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ee1d69502b33cbadca274575cb5df7fb25508564
scylladb/row_cache.cc
Glauber Costa 1d7617723d row cache: pin real dirty during cache updates. 
Right now, once a region is moved to the cache is no longer visible to
the dirty memory system. Not as real dirty nor virtual dirty.

The problem is that until a particular partition is moved to the cache
it is not evictable. As a result we can OOM the system if we have a lot
of pending cache updates as the writes will not be throttled and memory
won't be made available.

This patch pins the memory used by the region as real dirty before the
cache update starts, and unpins it when it is over. In the mean time it
gradually releases memory of the partitions that are being moved to
cache.

I have verified in a couple of workloads that the amount of memory
accounted through this is the same amount of memory accounted through
the memtable flush procedure.

Fixes #1942

Signed-off-by: Glauber Costa <glauber@scylladb.com>
2017-11-08 19:46:36 -05:00

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/*
* Copyright (C) 2015 ScyllaDB
*/
/*
* This file is part of Scylla.
*
* Scylla is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Scylla is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
*/
#include "row_cache.hh"
#include "core/memory.hh"
#include "core/do_with.hh"
#include "core/future-util.hh"
#include <seastar/core/metrics.hh>
#include <seastar/util/defer.hh>
#include "memtable.hh"
#include "partition_snapshot_reader.hh"
#include <chrono>
#include "utils/move.hh"
#include <boost/version.hpp>
#include <sys/sdt.h>
#include "stdx.hh"
#include "cache_streamed_mutation.hh"
#include "read_context.hh"
#include "schema_upgrader.hh"
#include "dirty_memory_manager.hh"
using namespace std::chrono_literals;
using namespace cache;
static logging::logger clogger("cache");
thread_local seastar::thread_scheduling_group row_cache::_update_thread_scheduling_group(1ms, 0.2);
mutation_reader
row_cache::create_underlying_reader(read_context& ctx, mutation_source& src, const dht::partition_range& pr) {
ctx.on_underlying_created();
return src(_schema, pr, ctx.slice(), ctx.pc(), ctx.trace_state(), streamed_mutation::forwarding::yes);
}
cache_tracker& global_cache_tracker() {
static thread_local cache_tracker instance;
return instance;
}
cache_tracker::cache_tracker() {
setup_metrics();
_region.make_evictable([this] {
return with_allocator(_region.allocator(), [this] {
// Removing a partition may require reading large keys when we rebalance
// the rbtree, so linearize anything we read
return with_linearized_managed_bytes([&] {
try {
auto evict_last = [this](lru_type& lru) {
cache_entry& ce = lru.back();
auto it = row_cache::partitions_type::s_iterator_to(ce);
clear_continuity(*std::next(it));
lru.pop_back_and_dispose(current_deleter<cache_entry>());
};
if (_lru.empty()) {
return memory::reclaiming_result::reclaimed_nothing;
}
evict_last(_lru);
--_stats.partitions;
++_stats.partition_evictions;
return memory::reclaiming_result::reclaimed_something;
} catch (std::bad_alloc&) {
// Bad luck, linearization during partition removal caused us to
// fail. Drop the entire cache so we can make forward progress.
clear();
return memory::reclaiming_result::reclaimed_something;
}
});
});
});
}
cache_tracker::~cache_tracker() {
clear();
}
void
cache_tracker::setup_metrics() {
namespace sm = seastar::metrics;
_metrics.add_group("cache", {
sm::make_gauge("bytes_used", sm::description("current bytes used by the cache out of the total size of memory"), [this] { return _region.occupancy().used_space(); }),
sm::make_gauge("bytes_total", sm::description("total size of memory for the cache"), [this] { return _region.occupancy().total_space(); }),
sm::make_derive("partition_hits", sm::description("number of partitions needed by reads and found in cache"), _stats.partition_hits),
sm::make_derive("partition_misses", sm::description("number of partitions needed by reads and missing in cache"), _stats.partition_misses),
sm::make_derive("partition_insertions", sm::description("total number of partitions added to cache"), _stats.partition_insertions),
sm::make_derive("row_hits", sm::description("total number of rows needed by reads and found in cache"), _stats.row_hits),
sm::make_derive("row_misses", sm::description("total number of rows needed by reads and missing in cache"), _stats.row_misses),
sm::make_derive("row_insertions", sm::description("total number of rows added to cache"), _stats.row_insertions),
sm::make_derive("concurrent_misses_same_key", sm::description("total number of operation with misses same key"), _stats.concurrent_misses_same_key),
sm::make_derive("partition_merges", sm::description("total number of partitions merged"), _stats.partition_merges),
sm::make_derive("partition_evictions", sm::description("total number of evicted partitions"), _stats.partition_evictions),
sm::make_derive("partition_removals", sm::description("total number of invalidated partitions"), _stats.partition_removals),
sm::make_derive("mispopulations", sm::description("number of entries not inserted by reads"), _stats.mispopulations),
sm::make_gauge("partitions", sm::description("total number of cached partitions"), _stats.partitions),
sm::make_derive("reads", sm::description("number of started reads"), _stats.reads),
sm::make_derive("reads_with_misses", sm::description("number of reads which had to read from sstables"), _stats.reads_with_misses),
sm::make_gauge("active_reads", sm::description("number of currently active reads"), [this] { return _stats.active_reads(); }),
sm::make_derive("sstable_reader_recreations", sm::description("number of times sstable reader was recreated due to memtable flush"), _stats.underlying_recreations),
sm::make_derive("sstable_partition_skips", sm::description("number of times sstable reader was fast forwarded across partitions"), _stats.underlying_partition_skips),
sm::make_derive("sstable_row_skips", sm::description("number of times sstable reader was fast forwarded within a partition"), _stats.underlying_row_skips),
sm::make_derive("pinned_dirty_memory_overload", sm::description("amount of pinned bytes that we tried to unpin over the limit. This should sit constantly at 0, and any number different than 0 is indicative of a bug"), _stats.pinned_dirty_memory_overload),
});
}
void cache_tracker::clear() {
with_allocator(_region.allocator(), [this] {
auto clear = [this] (lru_type& lru) {
while (!lru.empty()) {
cache_entry& ce = lru.back();
auto it = row_cache::partitions_type::s_iterator_to(ce);
while (it->is_evictable()) {
cache_entry& to_remove = *it;
++it;
to_remove._lru_link.unlink();
current_deleter<cache_entry>()(&to_remove);
}
clear_continuity(*it);
}
};
clear(_lru);
});
_stats.partition_removals += _stats.partitions;
_stats.partitions = 0;
allocator().invalidate_references();
}
void cache_tracker::touch(cache_entry& e) {
auto move_to_front = [this] (lru_type& lru, cache_entry& e) {
lru.erase(lru.iterator_to(e));
lru.push_front(e);
};
move_to_front(_lru, e);
}
void cache_tracker::insert(cache_entry& entry) {
++_stats.partition_insertions;
++_stats.partitions;
// partition_range_cursor depends on this to detect invalidation of _end
_region.allocator().invalidate_references();
_lru.push_front(entry);
}
void cache_tracker::on_erase() {
--_stats.partitions;
++_stats.partition_removals;
allocator().invalidate_references();
}
void cache_tracker::on_merge() {
++_stats.partition_merges;
}
void cache_tracker::on_partition_hit() {
++_stats.partition_hits;
}
void cache_tracker::on_partition_miss() {
++_stats.partition_misses;
}
void cache_tracker::on_row_hit() {
++_stats.row_hits;
}
void cache_tracker::on_row_miss() {
++_stats.row_misses;
}
void cache_tracker::on_mispopulate() {
++_stats.mispopulations;
}
void cache_tracker::on_miss_already_populated() {
++_stats.concurrent_misses_same_key;
}
void cache_tracker::pinned_dirty_memory_overload(uint64_t bytes) {
_stats.pinned_dirty_memory_overload += bytes;
}
allocation_strategy& cache_tracker::allocator() {
return _region.allocator();
}
logalloc::region& cache_tracker::region() {
return _region;
}
const logalloc::region& cache_tracker::region() const {
return _region;
}
// Stable cursor over partition entries from given range.
//
// Must be accessed with reclaim lock held on the cache region.
// The position of the cursor is always valid, but cache entry reference
// is not always valid. It remains valid as long as the iterators
// into _cache._partitions remain valid. Cache entry reference can be
// brought back to validity by calling refresh().
//
class partition_range_cursor final {
std::reference_wrapper<row_cache> _cache;
row_cache::partitions_type::iterator _it;
row_cache::partitions_type::iterator _end;
dht::ring_position_view _start_pos;
dht::ring_position_view _end_pos;
stdx::optional<dht::decorated_key> _last;
uint64_t _last_reclaim_count;
private:
void set_position(cache_entry& e) {
// FIXME: make ring_position_view convertible to ring_position, so we can use e.position()
if (e.is_dummy_entry()) {
_last = {};
_start_pos = dht::ring_position_view::max();
} else {
_last = e.key();
_start_pos = dht::ring_position_view(*_last);
}
}
public:
// Creates a cursor positioned at the lower bound of the range.
// The cache entry reference is not valid.
// The range reference must remain live as long as this instance is used.
partition_range_cursor(row_cache& cache, const dht::partition_range& range)
: _cache(cache)
, _start_pos(dht::ring_position_view::for_range_start(range))
, _end_pos(dht::ring_position_view::for_range_end(range))
, _last_reclaim_count(std::numeric_limits<uint64_t>::max())
{ }
// Ensures that cache entry reference is valid.
// The cursor will point at the first entry with position >= the current position.
// Returns true if and only if the position of the cursor changed.
// Strong exception guarantees.
bool refresh() {
auto reclaim_count = _cache.get().get_cache_tracker().allocator().invalidate_counter();
if (reclaim_count == _last_reclaim_count) {
return true;
}
auto cmp = cache_entry::compare(_cache.get()._schema);
if (cmp(_end_pos, _start_pos)) { // next() may have moved _start_pos past the _end_pos.
_end_pos = _start_pos;
}
_end = _cache.get()._partitions.lower_bound(_end_pos, cmp);
_it = _cache.get()._partitions.lower_bound(_start_pos, cmp);
auto same = !cmp(_start_pos, _it->position());
set_position(*_it);
_last_reclaim_count = reclaim_count;
return same;
}
// Positions the cursor at the next entry.
// May advance past the requested range. Use in_range() after the call to determine that.
// Call only when in_range() and cache entry reference is valid.
// Strong exception guarantees.
void next() {
auto next = std::next(_it);
set_position(*next);
_it = std::move(next);
}
// Valid only after refresh() and before _cache._partitions iterators are invalidated.
// Points inside the requested range if in_range().
cache_entry& entry() {
return *_it;
}
// Call only when cache entry reference is valid.
bool in_range() {
return _it != _end;
}
// Returns current position of the cursor.
// Result valid as long as this instance is valid and not advanced.
dht::ring_position_view position() const {
return _start_pos;
}
};
future<> read_context::create_sm() {
if (_range_query) {
// FIXME: Singular-range mutation readers don't support fast_forward_to(), so need to use a wide range
// here in case the same reader will need to be fast forwarded later.
_sm_range = dht::partition_range({dht::ring_position(*_key)}, {dht::ring_position(*_key)});
} else {
_sm_range = dht::partition_range::make_singular({dht::ring_position(*_key)});
}
return _underlying.fast_forward_to(std::move(_sm_range), *_underlying_snapshot, _phase).then([this] {
return _underlying.read_next_same_phase().then([this] (auto&& smo) {
if (!smo) {
_sm = make_empty_streamed_mutation(_cache.schema(), *_key, streamed_mutation::forwarding::yes);
} else {
_sm = std::move(*smo);
}
});
});
}
static streamed_mutation read_directly_from_underlying(streamed_mutation&& sm, read_context& reader) {
if (reader.schema()->version() != sm.schema()->version()) {
sm = transform(std::move(sm), schema_upgrader(reader.schema()));
}
if (reader.fwd() == streamed_mutation::forwarding::no) {
sm = streamed_mutation_from_forwarding_streamed_mutation(std::move(sm));
}
return std::move(sm);
}
// Reader which populates the cache using data from the delegate.
class single_partition_populating_reader final : public mutation_reader::impl {
row_cache& _cache;
mutation_reader _delegate;
lw_shared_ptr<read_context> _read_context;
public:
single_partition_populating_reader(row_cache& cache,
lw_shared_ptr<read_context> context)
: _cache(cache)
, _read_context(std::move(context))
{ }
virtual future<streamed_mutation_opt> operator()() override {
if (!_read_context) {
return make_ready_future<streamed_mutation_opt>(streamed_mutation_opt());
}
auto src_and_phase = _cache.snapshot_of(_read_context->range().start()->value());
auto phase = src_and_phase.phase;
_delegate = _cache.create_underlying_reader(*_read_context, src_and_phase.snapshot, _read_context->range());
return _delegate().then([this, phase] (auto sm) mutable -> streamed_mutation_opt {
auto ctx = std::move(_read_context);
if (!sm) {
if (phase == _cache.phase_of(ctx->range().start()->value())) {
_cache._read_section(_cache._tracker.region(), [this, ctx = std::move(ctx)] {
with_allocator(_cache._tracker.allocator(), [this, &ctx] {
dht::decorated_key dk = ctx->range().start()->value().as_decorated_key();
_cache.do_find_or_create_entry(dk, nullptr, [&] (auto i) {
mutation_partition mp(_cache._schema);
cache_entry* entry = current_allocator().construct<cache_entry>(
_cache._schema, std::move(dk), std::move(mp));
_cache._tracker.insert(*entry);
entry->set_continuous(i->continuous());
return _cache._partitions.insert(i, *entry);
}, [&] (auto i) {
_cache._tracker.on_miss_already_populated();
});
});
});
} else {
_cache._tracker.on_mispopulate();
}
return std::move(sm);
}
if (phase == _cache.phase_of(ctx->range().start()->value())) {
return _cache._read_section(_cache._tracker.region(), [&] {
cache_entry& e = _cache.find_or_create(sm->decorated_key(), sm->partition_tombstone(), phase);
return e.read(_cache, *ctx, std::move(*sm), phase);
});
} else {
_cache._tracker.on_mispopulate();
return read_directly_from_underlying(std::move(*sm), *ctx);
}
});
}
};
void cache_tracker::clear_continuity(cache_entry& ce) {
ce.set_continuous(false);
}
void row_cache::on_partition_hit() {
_tracker.on_partition_hit();
}
void row_cache::on_partition_miss() {
_tracker.on_partition_miss();
}
void row_cache::on_row_hit() {
_stats.hits.mark();
_tracker.on_row_hit();
}
void row_cache::on_mispopulate() {
_tracker.on_mispopulate();
}
void row_cache::on_row_miss() {
_stats.misses.mark();
_tracker.on_row_miss();
}
void row_cache::on_row_insert() {
++_tracker._stats.row_insertions;
}
class range_populating_reader {
row_cache& _cache;
autoupdating_underlying_reader& _reader;
stdx::optional<row_cache::previous_entry_pointer> _last_key;
read_context& _read_context;
private:
bool can_set_continuity() const {
return _last_key && _reader.creation_phase() == _cache.phase_of(_reader.population_range_start());
}
void handle_end_of_stream() {
if (!can_set_continuity()) {
_cache.on_mispopulate();
return;
}
if (!_reader.range().end() || !_reader.range().end()->is_inclusive()) {
cache_entry::compare cmp(_cache._schema);
auto it = _reader.range().end() ? _cache._partitions.find(_reader.range().end()->value(), cmp)
: std::prev(_cache._partitions.end());
if (it != _cache._partitions.end()) {
if (it == _cache._partitions.begin()) {
if (!_last_key->_key) {
it->set_continuous(true);
} else {
_cache.on_mispopulate();
}
} else {
auto prev = std::prev(it);
if (prev->key().equal(*_cache._schema, *_last_key->_key)) {
it->set_continuous(true);
} else {
_cache.on_mispopulate();
}
}
}
}
}
public:
range_populating_reader(row_cache& cache, read_context& ctx)
: _cache(cache)
, _reader(ctx.underlying())
, _read_context(ctx)
{}
future<streamed_mutation_opt> operator()() {
return _reader().then([this] (streamed_mutation_opt smopt) mutable -> streamed_mutation_opt {
{
if (!smopt) {
handle_end_of_stream();
return std::move(smopt);
}
_cache.on_partition_miss();
if (_reader.creation_phase() == _cache.phase_of(smopt->decorated_key())) {
return _cache._read_section(_cache._tracker.region(), [&] {
cache_entry& e = _cache.find_or_create(smopt->decorated_key(), smopt->partition_tombstone(), _reader.creation_phase(),
can_set_continuity() ? &*_last_key : nullptr);
_last_key = row_cache::previous_entry_pointer(smopt->decorated_key());
return e.read(_cache, _read_context, std::move(*smopt), _reader.creation_phase());
});
} else {
_cache._tracker.on_mispopulate();
_last_key = row_cache::previous_entry_pointer(smopt->decorated_key());
return read_directly_from_underlying(std::move(*smopt), _read_context);
}
}
});
}
future<> fast_forward_to(dht::partition_range&& pr) {
if (!pr.start()) {
_last_key = row_cache::previous_entry_pointer();
} else if (!pr.start()->is_inclusive() && pr.start()->value().has_key()) {
_last_key = row_cache::previous_entry_pointer(pr.start()->value().as_decorated_key());
} else {
// Inclusive start bound, cannot set continuity flag.
_last_key = {};
}
return _reader.fast_forward_to(std::move(pr));
}
};
class scanning_and_populating_reader final : public mutation_reader::impl {
const dht::partition_range* _pr;
row_cache& _cache;
lw_shared_ptr<read_context> _read_context;
partition_range_cursor _primary;
range_populating_reader _secondary_reader;
bool _secondary_in_progress = false;
bool _advance_primary = false;
stdx::optional<dht::partition_range::bound> _lower_bound;
dht::partition_range _secondary_range;
private:
streamed_mutation read_from_entry(cache_entry& ce) {
_cache.upgrade_entry(ce);
_cache._tracker.touch(ce);
_cache.on_partition_hit();
return ce.read(_cache, *_read_context);
}
streamed_mutation_opt do_read_from_primary() {
return _cache._read_section(_cache._tracker.region(), [this] {
return with_linearized_managed_bytes([&] () -> streamed_mutation_opt {
auto not_moved = _primary.refresh();
if (_advance_primary && not_moved) {
_primary.next();
not_moved = false;
}
_advance_primary = false;
if (not_moved || _primary.entry().continuous()) {
if (!_primary.in_range()) {
return stdx::nullopt;
}
cache_entry& e = _primary.entry();
auto sm = read_from_entry(e);
_lower_bound = dht::partition_range::bound{e.key(), false};
// Delay the call to next() so that we don't see stale continuity on next invocation.
_advance_primary = true;
return streamed_mutation_opt(std::move(sm));
} else {
if (_primary.in_range()) {
cache_entry& e = _primary.entry();
_secondary_range = dht::partition_range(_lower_bound ? std::move(_lower_bound) : _pr->start(),
dht::partition_range::bound{e.key(), false});
_lower_bound = dht::partition_range::bound{e.key(), true};
_secondary_in_progress = true;
return stdx::nullopt;
} else {
dht::ring_position_comparator cmp(*_read_context->schema());
auto range = _pr->trim_front(std::move(_lower_bound), cmp);
if (!range) {
return stdx::nullopt;
}
_lower_bound = dht::partition_range::bound{dht::ring_position::max()};
_secondary_range = std::move(*range);
_secondary_in_progress = true;
return stdx::nullopt;
}
}
});
});
}
future<streamed_mutation_opt> read_from_primary() {
auto smo = do_read_from_primary();
if (!_secondary_in_progress) {
return make_ready_future<streamed_mutation_opt>(std::move(smo));
}
return _secondary_reader.fast_forward_to(std::move(_secondary_range)).then([this] {
return read_from_secondary();
});
}
future<streamed_mutation_opt> read_from_secondary() {
return _secondary_reader().then([this] (streamed_mutation_opt smopt) {
if (smopt) {
return make_ready_future<streamed_mutation_opt>(std::move(smopt));
} else {
_secondary_in_progress = false;
return read_from_primary();
}
});
}
public:
scanning_and_populating_reader(row_cache& cache,
const dht::partition_range& range,
lw_shared_ptr<read_context> context)
: _pr(&range)
, _cache(cache)
, _read_context(std::move(context))
, _primary(cache, range)
, _secondary_reader(cache, *_read_context)
{ }
future<streamed_mutation_opt> operator()() {
if (_secondary_in_progress) {
return read_from_secondary();
} else {
return read_from_primary();
}
}
future<> fast_forward_to(const dht::partition_range& pr) {
_secondary_in_progress = false;
_advance_primary = false;
_pr = &pr;
_primary = partition_range_cursor{_cache, pr};
_lower_bound = {};
return make_ready_future<>();
}
};
mutation_reader
row_cache::make_scanning_reader(const dht::partition_range& range, lw_shared_ptr<read_context> context) {
return make_mutation_reader<scanning_and_populating_reader>(*this, range, std::move(context));
}
mutation_reader
row_cache::make_reader(schema_ptr s,
const dht::partition_range& range,
const query::partition_slice& slice,
const io_priority_class& pc,
tracing::trace_state_ptr trace_state,
streamed_mutation::forwarding fwd,
mutation_reader::forwarding fwd_mr)
{
auto ctx = make_lw_shared<read_context>(*this, std::move(s), range, slice, pc, trace_state, fwd, fwd_mr);
if (!ctx->is_range_query()) {
return _read_section(_tracker.region(), [&] {
return with_linearized_managed_bytes([&] {
cache_entry::compare cmp(_schema);
auto&& pos = ctx->range().start()->value();
auto i = _partitions.lower_bound(pos, cmp);
if (i != _partitions.end() && !cmp(pos, i->position())) {
cache_entry& e = *i;
_tracker.touch(e);
upgrade_entry(e);
on_partition_hit();
return make_reader_returning(e.read(*this, *ctx));
} else if (i->continuous()) {
return make_empty_reader();
} else {
on_partition_miss();
return make_mutation_reader<single_partition_populating_reader>(*this, std::move(ctx));
}
});
});
}
return make_scanning_reader(range, std::move(ctx));
}
row_cache::~row_cache() {
with_allocator(_tracker.allocator(), [this] {
_partitions.clear_and_dispose([this, deleter = current_deleter<cache_entry>()] (auto&& p) mutable {
if (!p->is_dummy_entry()) {
_tracker.on_erase();
}
deleter(p);
});
});
}
void row_cache::clear_now() noexcept {
with_allocator(_tracker.allocator(), [this] {
auto it = _partitions.erase_and_dispose(_partitions.begin(), partitions_end(), [this, deleter = current_deleter<cache_entry>()] (auto&& p) mutable {
_tracker.on_erase();
deleter(p);
});
_tracker.clear_continuity(*it);
});
}
template<typename CreateEntry, typename VisitEntry>
//requires requires(CreateEntry create, VisitEntry visit, row_cache::partitions_type::iterator it) {
// { create(it) } -> row_cache::partitions_type::iterator;
// { visit(it) } -> void;
// }
cache_entry& row_cache::do_find_or_create_entry(const dht::decorated_key& key,
const previous_entry_pointer* previous, CreateEntry&& create_entry, VisitEntry&& visit_entry)
{
return with_allocator(_tracker.allocator(), [&] () -> cache_entry& {
return with_linearized_managed_bytes([&] () -> cache_entry& {
auto i = _partitions.lower_bound(key, cache_entry::compare(_schema));
if (i == _partitions.end() || !i->key().equal(*_schema, key)) {
i = create_entry(i);
} else {
visit_entry(i);
}
if (!previous) {
return *i;
}
if ((!previous->_key && i == _partitions.begin())
|| (previous->_key && i != _partitions.begin()
&& std::prev(i)->key().equal(*_schema, *previous->_key))) {
i->set_continuous(true);
} else {
on_mispopulate();
}
return *i;
});
});
}
cache_entry& row_cache::find_or_create(const dht::decorated_key& key, tombstone t, row_cache::phase_type phase, const previous_entry_pointer* previous) {
return do_find_or_create_entry(key, previous, [&] (auto i) { // create
auto entry = current_allocator().construct<cache_entry>(cache_entry::incomplete_tag{}, _schema, key, t);
_tracker.insert(*entry);
return _partitions.insert(i, *entry);
}, [&] (auto i) { // visit
_tracker.on_miss_already_populated();
cache_entry& e = *i;
e.partition().open_version(*e.schema(), phase).partition().apply(t);
_tracker.touch(e);
upgrade_entry(e);
});
}
void row_cache::populate(const mutation& m, const previous_entry_pointer* previous) {
_populate_section(_tracker.region(), [&] {
do_find_or_create_entry(m.decorated_key(), previous, [&] (auto i) {
cache_entry* entry = current_allocator().construct<cache_entry>(
m.schema(), m.decorated_key(), m.partition());
upgrade_entry(*entry);
_tracker.insert(*entry);
entry->set_continuous(i->continuous());
return _partitions.insert(i, *entry);
}, [&] (auto i) {
throw std::runtime_error(sprint("cache already contains entry for {}", m.key()));
});
});
}
mutation_source& row_cache::snapshot_for_phase(phase_type phase) {
if (phase == _underlying_phase) {
return _underlying;
} else {
if (phase + 1 < _underlying_phase) {
throw std::runtime_error(sprint("attempted to read from retired phase {} (current={})", phase, _underlying_phase));
}
return *_prev_snapshot;
}
}
row_cache::snapshot_and_phase row_cache::snapshot_of(dht::ring_position_view pos) {
dht::ring_position_less_comparator less(*_schema);
if (!_prev_snapshot_pos || less(pos, *_prev_snapshot_pos)) {
return {_underlying, _underlying_phase};
}
return {*_prev_snapshot, _underlying_phase - 1};
}
void row_cache::invalidate_sync(memtable& m) noexcept {
with_allocator(_tracker.allocator(), [&m, this] () {
logalloc::reclaim_lock _(_tracker.region());
bool blow_cache = false;
// Note: clear_and_dispose() ought not to look up any keys, so it doesn't require
// with_linearized_managed_bytes(), but invalidate() does.
m.partitions.clear_and_dispose([this, deleter = current_deleter<memtable_entry>(), &blow_cache] (memtable_entry* entry) {
with_linearized_managed_bytes([&] {
try {
invalidate_locked(entry->key());
} catch (...) {
blow_cache = true;
}
deleter(entry);
});
});
if (blow_cache) {
// We failed to invalidate the key, presumably due to with_linearized_managed_bytes()
// running out of memory. Recover using clear_now(), which doesn't throw.
clear_now();
}
});
}
row_cache::phase_type row_cache::phase_of(dht::ring_position_view pos) {
dht::ring_position_less_comparator less(*_schema);
if (!_prev_snapshot_pos || less(pos, *_prev_snapshot_pos)) {
return _underlying_phase;
}
return _underlying_phase - 1;
}
// makes sure that cache updates handles real dirty memory correctly.
class real_dirty_memory_accounter {
dirty_memory_manager& _mgr;
cache_tracker& _tracker;
uint64_t _bytes;
public:
real_dirty_memory_accounter(memtable& m, cache_tracker& tracker)
: _mgr(m.get_dirty_memory_manager())
, _tracker(tracker)
, _bytes(m.occupancy().used_space()) {
_mgr.pin_real_dirty_memory(_bytes);
}
~real_dirty_memory_accounter() {
_mgr.unpin_real_dirty_memory(_bytes);
}
real_dirty_memory_accounter(real_dirty_memory_accounter&& c) : _mgr(c._mgr), _tracker(c._tracker), _bytes(c._bytes) {
c._bytes = 0;
}
real_dirty_memory_accounter(const real_dirty_memory_accounter& c) = delete;
void unpin_memory(uint64_t bytes) {
// this should never happen - if it does it is a bug. But we'll try to recover and log
// instead of asserting. Once it happens, though, it can keep happening until the update is
// done. So using metrics is better-suited than printing to the logs
if (bytes > _bytes) {
_tracker.pinned_dirty_memory_overload(bytes - _bytes);
}
auto delta = std::min(bytes, _bytes);
_bytes -= delta;
_mgr.unpin_real_dirty_memory(delta);
}
};
template <typename Updater>
future<> row_cache::do_update(external_updater eu, memtable& m, Updater updater) {
return do_update(std::move(eu), [this, &m, updater = std::move(updater)] {
real_dirty_memory_accounter real_dirty_acc(m, _tracker);
m.on_detach_from_region_group();
_tracker.region().merge(m); // Now all data in memtable belongs to cache
STAP_PROBE(scylla, row_cache_update_start);
auto cleanup = defer([&m, this] {
invalidate_sync(m);
STAP_PROBE(scylla, row_cache_update_end);
});
auto attr = seastar::thread_attributes();
attr.scheduling_group = &_update_thread_scheduling_group;
return seastar::async(std::move(attr), [this, &m, updater = std::move(updater), real_dirty_acc = std::move(real_dirty_acc)] () mutable {
// In case updater fails, we must bring the cache to consistency without deferring.
auto cleanup = defer([&m, this] {
invalidate_sync(m);
_prev_snapshot_pos = {};
_prev_snapshot = {};
});
partition_presence_checker is_present = _prev_snapshot->make_partition_presence_checker();
while (!m.partitions.empty()) {
with_allocator(_tracker.allocator(), [&] () {
unsigned quota = 30;
auto cmp = cache_entry::compare(_schema);
{
_update_section(_tracker.region(), [&] {
STAP_PROBE(scylla, row_cache_update_one_batch_start);
unsigned quota_before = quota;
// FIXME: we should really be checking should_yield() here instead of
// need_preempt() + quota. However, should_yield() is currently quite
// expensive and we need to amortize it somehow.
do {
auto i = m.partitions.begin();
STAP_PROBE(scylla, row_cache_update_partition_start);
with_linearized_managed_bytes([&] {
{
memtable_entry& mem_e = *i;
auto size_entry = mem_e.size_in_allocator(_tracker.allocator());
// FIXME: Optimize knowing we lookup in-order.
auto cache_i = _partitions.lower_bound(mem_e.key(), cmp);
updater(cache_i, mem_e, is_present);
real_dirty_acc.unpin_memory(size_entry);
i = m.partitions.erase(i);
current_allocator().destroy(&mem_e);
--quota;
}
});
STAP_PROBE(scylla, row_cache_update_partition_end);
} while (!m.partitions.empty() && quota && !need_preempt());
with_allocator(standard_allocator(), [&] {
if (m.partitions.empty()) {
_prev_snapshot_pos = {};
} else {
_prev_snapshot_pos = dht::ring_position(m.partitions.begin()->key());
}
});
STAP_PROBE1(scylla, row_cache_update_one_batch_end, quota_before - quota);
});
if (quota == 0 && seastar::thread::should_yield()) {
return;
}
}
});
seastar::thread::yield();
}
}).finally([cleanup = std::move(cleanup)] {});
});
}
future<> row_cache::update(external_updater eu, memtable& m) {
return do_update(std::move(eu), m, [this] (row_cache::partitions_type::iterator cache_i, memtable_entry& mem_e,
partition_presence_checker& is_present) mutable {
// If cache doesn't contain the entry we cannot insert it because the mutation may be incomplete.
// FIXME: keep a bitmap indicating which sstables we do cover, so we don't have to
// search it.
if (cache_i != partitions_end() && cache_i->key().equal(*_schema, mem_e.key())) {
cache_entry& entry = *cache_i;
upgrade_entry(entry);
entry.partition().apply_to_incomplete(*_schema, std::move(mem_e.partition()), *mem_e.schema());
_tracker.touch(entry);
_tracker.on_merge();
} else if (cache_i->continuous() || is_present(mem_e.key()) == partition_presence_checker_result::definitely_doesnt_exist) {
cache_entry* entry = current_allocator().construct<cache_entry>(
mem_e.schema(), std::move(mem_e.key()), std::move(mem_e.partition()));
entry->set_continuous(cache_i->continuous());
_tracker.insert(*entry);
_partitions.insert(cache_i, *entry);
}
});
}
future<> row_cache::update_invalidating(external_updater eu, memtable& m) {
return do_update(std::move(eu), m, [this] (row_cache::partitions_type::iterator cache_i, memtable_entry& mem_e,
partition_presence_checker& is_present) {
if (cache_i != partitions_end() && cache_i->key().equal(*_schema, mem_e.key())) {
// FIXME: Invalidate only affected row ranges.
// This invalidates all row ranges and the static row, leaving only the partition tombstone continuous,
// which has to always be continuous.
cache_entry& e = *cache_i;
e.partition().evict(); // FIXME: evict gradually
upgrade_entry(e);
e.partition().apply_to_incomplete(*_schema, std::move(mem_e.partition()), *mem_e.schema());
} else {
_tracker.clear_continuity(*cache_i);
}
});
}
void row_cache::refresh_snapshot() {
_underlying = _snapshot_source();
}
void row_cache::touch(const dht::decorated_key& dk) {
_read_section(_tracker.region(), [&] {
with_linearized_managed_bytes([&] {
auto i = _partitions.find(dk, cache_entry::compare(_schema));
if (i != _partitions.end()) {
_tracker.touch(*i);
}
});
});
}
void row_cache::invalidate_locked(const dht::decorated_key& dk) {
auto pos = _partitions.lower_bound(dk, cache_entry::compare(_schema));
if (pos == partitions_end() || !pos->key().equal(*_schema, dk)) {
_tracker.clear_continuity(*pos);
} else {
auto it = _partitions.erase_and_dispose(pos,
[this, &dk, deleter = current_deleter<cache_entry>()](auto&& p) mutable {
_tracker.on_erase();
deleter(p);
});
_tracker.clear_continuity(*it);
}
}
future<> row_cache::invalidate(external_updater eu, const dht::decorated_key& dk) {
return invalidate(std::move(eu), dht::partition_range::make_singular(dk));
}
future<> row_cache::invalidate(external_updater eu, const dht::partition_range& range) {
return invalidate(std::move(eu), dht::partition_range_vector({range}));
}
future<> row_cache::invalidate(external_updater eu, dht::partition_range_vector&& ranges) {
return do_update(std::move(eu), [this, ranges = std::move(ranges)] {
auto on_failure = defer([this] { this->clear_now(); });
with_linearized_managed_bytes([&] {
for (auto&& range : ranges) {
this->invalidate_unwrapped(range);
}
});
on_failure.cancel();
return make_ready_future<>();
});
}
void row_cache::evict(const dht::partition_range& range) {
invalidate_unwrapped(range);
}
void row_cache::invalidate_unwrapped(const dht::partition_range& range) {
logalloc::reclaim_lock _(_tracker.region());
auto cmp = cache_entry::compare(_schema);
auto begin = _partitions.lower_bound(dht::ring_position_view::for_range_start(range), cmp);
auto end = _partitions.lower_bound(dht::ring_position_view::for_range_end(range), cmp);
with_allocator(_tracker.allocator(), [this, begin, end] {
auto it = _partitions.erase_and_dispose(begin, end, [this, deleter = current_deleter<cache_entry>()] (auto&& p) mutable {
_tracker.on_erase();
deleter(p);
});
assert(it != _partitions.end());
_tracker.clear_continuity(*it);
});
}
row_cache::row_cache(schema_ptr s, snapshot_source src, cache_tracker& tracker, is_continuous cont)
: _tracker(tracker)
, _schema(std::move(s))
, _partitions(cache_entry::compare(_schema))
, _underlying(src())
, _snapshot_source(std::move(src))
{
with_allocator(_tracker.allocator(), [this, cont] {
cache_entry* entry = current_allocator().construct<cache_entry>(cache_entry::dummy_entry_tag());
_partitions.insert(*entry);
entry->set_continuous(bool(cont));
});
}
cache_entry::cache_entry(cache_entry&& o) noexcept
: _schema(std::move(o._schema))
, _key(std::move(o._key))
, _pe(std::move(o._pe))
, _flags(o._flags)
, _lru_link()
, _cache_link()
{
if (o._lru_link.is_linked()) {
auto prev = o._lru_link.prev_;
o._lru_link.unlink();
cache_tracker::lru_type::node_algorithms::link_after(prev, _lru_link.this_ptr());
}
{
using container_type = row_cache::partitions_type;
container_type::node_algorithms::replace_node(o._cache_link.this_ptr(), _cache_link.this_ptr());
container_type::node_algorithms::init(o._cache_link.this_ptr());
}
}
cache_entry::~cache_entry() {
_pe.evict();
}
void row_cache::set_schema(schema_ptr new_schema) noexcept {
_schema = std::move(new_schema);
}
streamed_mutation cache_entry::read(row_cache& rc, read_context& reader) {
auto source_and_phase = rc.snapshot_of(_key);
reader.enter_partition(_key, source_and_phase.snapshot, source_and_phase.phase);
return do_read(rc, reader);
}
streamed_mutation cache_entry::read(row_cache& rc, read_context& reader,
streamed_mutation&& sm, row_cache::phase_type phase) {
reader.enter_partition(std::move(sm), phase);
return do_read(rc, reader);
}
// Assumes reader is in the corresponding partition
streamed_mutation cache_entry::do_read(row_cache& rc, read_context& reader) {
auto snp = _pe.read(rc._tracker.region(), _schema, reader.phase());
auto ckr = query::clustering_key_filter_ranges::get_ranges(*_schema, reader.slice(), _key.key());
auto sm = make_cache_streamed_mutation(_schema, _key, std::move(ckr), rc, reader.shared_from_this(), std::move(snp));
if (reader.schema()->version() != _schema->version()) {
sm = transform(std::move(sm), schema_upgrader(reader.schema()));
}
if (reader.fwd() == streamed_mutation::forwarding::yes) {
sm = make_forwardable(std::move(sm));
}
return std::move(sm);
}
const schema_ptr& row_cache::schema() const {
return _schema;
}
void row_cache::upgrade_entry(cache_entry& e) {
if (e._schema != _schema) {
auto& r = _tracker.region();
assert(!r.reclaiming_enabled());
with_allocator(r.allocator(), [this, &e] {
with_linearized_managed_bytes([&] {
e.partition().upgrade(e._schema, _schema);
e._schema = _schema;
});
});
}
}
std::ostream& operator<<(std::ostream& out, row_cache& rc) {
rc._read_section(rc._tracker.region(), [&] {
out << "{row_cache: " << ::join(", ", rc._partitions.begin(), rc._partitions.end()) << "}";
});
return out;
}
future<> row_cache::do_update(row_cache::external_updater eu, row_cache::internal_updater iu) noexcept {
return futurize_apply([this] {
return get_units(_update_sem, 1);
}).then([this, eu = std::move(eu), iu = std::move(iu)] (auto permit) mutable {
auto pos = dht::ring_position::min();
eu();
[&] () noexcept {
_prev_snapshot_pos = std::move(pos);
_prev_snapshot = std::exchange(_underlying, _snapshot_source());
++_underlying_phase;
}();
return futurize_apply([&iu] {
return iu();
}).then_wrapped([this, permit = std::move(permit)] (auto f) {
_prev_snapshot_pos = {};
_prev_snapshot = {};
if (f.failed()) {
clogger.warn("Failure during cache update: {}", f.get_exception());
}
});
});
}
std::ostream& operator<<(std::ostream& out, cache_entry& e) {
return out << "{cache_entry: " << e.position()
<< ", cont=" << e.continuous()
<< ", dummy=" << e.is_dummy_entry()
<< ", " << e.partition()
<< "}";
}
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