83b004b2fb
Originally, lsa allocated each segment independently what could result in high memory fragmentation. As a result many compaction and eviction passes may be needed to release a sufficiently big contiguous memory block. These problems are solved by introduction of segment zones, contiguous groups of segments. All segments are allocated from zones and the algorithm tries to keep the number of zones to a minimum. Moreover, segments can be migrated between zones or inside a zone in order to deal with fragmentation inside zone. Segment zones can be shrunk but cannot grow. Segment pool keeps a tree containing all zones ordered by their base addresses. This tree is used only by the memory reclamer. There is also a list of zones that have at least one free segments that is used during allocation. Segment allocation doesn't have any preferences which segment (and zone) to choose. Each zone contains a free list of unused segments. If there are no zones with free segments a new one is created. Segment reclamation migrates segments from the zones higher in memory to the ones at lower addresses. The remaining zones are shrunk until the requested number of segments is reclaimed. Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
250 lines
9.9 KiB
C++
250 lines
9.9 KiB
C++
/*
|
|
* Copyright 2015 Cloudius Systems
|
|
*/
|
|
|
|
/*
|
|
* 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 <core/distributed.hh>
|
|
#include <core/app-template.hh>
|
|
#include <core/sstring.hh>
|
|
#include <core/thread.hh>
|
|
|
|
#include "utils/managed_bytes.hh"
|
|
#include "utils/logalloc.hh"
|
|
#include "row_cache.hh"
|
|
#include "log.hh"
|
|
#include "schema_builder.hh"
|
|
#include "memtable.hh"
|
|
|
|
static
|
|
partition_key new_key(schema_ptr s) {
|
|
static thread_local int next = 0;
|
|
return partition_key::from_single_value(*s, to_bytes(sprint("key%d", next++)));
|
|
}
|
|
|
|
static
|
|
clustering_key new_ckey(schema_ptr s) {
|
|
static thread_local int next = 0;
|
|
return clustering_key::from_single_value(*s, to_bytes(sprint("ckey%d", next++)));
|
|
}
|
|
|
|
int main(int argc, char** argv) {
|
|
namespace bpo = boost::program_options;
|
|
app_template app;
|
|
app.add_options()
|
|
("debug", "enable debug logging");
|
|
|
|
return app.run(argc, argv, [&app] {
|
|
if (app.configuration().count("debug")) {
|
|
logging::logger_registry().set_all_loggers_level(logging::log_level::debug);
|
|
}
|
|
|
|
// This test is supposed to verify that when we're low on memory but
|
|
// we still have plenty of evictable memory in cache, we should be
|
|
// able to populate cache with large mutations This test works only
|
|
// with seastar's allocator.
|
|
return seastar::async([] {
|
|
auto s = schema_builder("ks", "cf")
|
|
.with_column("pk", bytes_type, column_kind::partition_key)
|
|
.with_column("ck", bytes_type, column_kind::clustering_key)
|
|
.with_column("v", bytes_type, column_kind::regular_column)
|
|
.build();
|
|
|
|
auto mt = make_lw_shared<memtable>(s);
|
|
|
|
cache_tracker tracker;
|
|
row_cache cache(s, mt->as_data_source(), mt->as_key_source(), tracker);
|
|
|
|
std::vector<dht::decorated_key> keys;
|
|
|
|
size_t cell_size = 1024;
|
|
size_t row_count = 40 * 1024; // 40M mutations
|
|
|
|
auto make_small_mutation = [&] {
|
|
mutation m(new_key(s), s);
|
|
m.set_clustered_cell(new_ckey(s), "v", data_value(bytes(bytes::initialized_later(), cell_size)), 1);
|
|
return m;
|
|
};
|
|
|
|
auto make_large_mutation = [&] {
|
|
mutation m(new_key(s), s);
|
|
for (size_t j = 0; j < row_count; j++) {
|
|
m.set_clustered_cell(new_ckey(s), "v", data_value(bytes(bytes::initialized_later(), cell_size)), 2);
|
|
}
|
|
return m;
|
|
};
|
|
|
|
for (int i = 0; i < 10; i++) {
|
|
auto key = dht::global_partitioner().decorate_key(*s, new_key(s));
|
|
|
|
mutation m1(key, s);
|
|
m1.set_clustered_cell(new_ckey(s), "v", data_value(bytes(bytes::initialized_later(), cell_size)), 1);
|
|
cache.populate(m1);
|
|
|
|
// Putting large mutations into the memtable. Should take about row_count*cell_size each.
|
|
mutation m2(key, s);
|
|
for (size_t j = 0; j < row_count; j++) {
|
|
m2.set_clustered_cell(new_ckey(s), "v", data_value(bytes(bytes::initialized_later(), cell_size)), 2);
|
|
}
|
|
|
|
mt->apply(m2);
|
|
keys.push_back(key);
|
|
}
|
|
|
|
std::cout << "memtable occupancy: " << mt->occupancy() << "\n";
|
|
std::cout << "Cache occupancy: " << tracker.region().occupancy() << "\n";
|
|
std::cout << "Free memory: " << memory::stats().free_memory() << "\n";
|
|
|
|
// We need to have enough Free memory to copy memtable into cache
|
|
// When this assertion fails, increase amount of memory
|
|
assert(mt->occupancy().used_space() < memory::stats().free_memory());
|
|
|
|
auto checker = [](const partition_key& key) {
|
|
return partition_presence_checker_result::maybe_exists;
|
|
};
|
|
|
|
std::deque<dht::decorated_key> cache_stuffing;
|
|
auto fill_cache_to_the_top = [&] {
|
|
std::cout << "Filling up memory with evictable data\n";
|
|
while (true) {
|
|
// Ensure that entries matching memtable partitions are evicted
|
|
// last, we want to hit the merge path in row_cache::update()
|
|
for (auto&& key : keys) {
|
|
cache.touch(key);
|
|
}
|
|
auto occupancy_before = tracker.region().occupancy().used_space();
|
|
auto m = make_small_mutation();
|
|
cache_stuffing.push_back(m.decorated_key());
|
|
cache.populate(m);
|
|
if (tracker.region().occupancy().used_space() <= occupancy_before) {
|
|
break;
|
|
}
|
|
}
|
|
std::cout << "Shuffling..\n";
|
|
// Evict in random order to create fragmentation.
|
|
std::random_shuffle(cache_stuffing.begin(), cache_stuffing.end());
|
|
for (auto&& key : cache_stuffing) {
|
|
cache.touch(key);
|
|
}
|
|
// Ensure that entries matching memtable partitions are evicted
|
|
// last, we want to hit the merge path in row_cache::update()
|
|
for (auto&& key : keys) {
|
|
cache.touch(key);
|
|
}
|
|
std::cout << "Free memory: " << memory::stats().free_memory() << "\n";
|
|
std::cout << "Cache occupancy: " << tracker.region().occupancy() << "\n";
|
|
};
|
|
|
|
std::deque<std::unique_ptr<char[]>> stuffing;
|
|
auto fragment_free_space = [&] {
|
|
stuffing.clear();
|
|
std::cout << "Free memory: " << memory::stats().free_memory() << "\n";
|
|
std::cout << "Cache occupancy: " << tracker.region().occupancy() << "\n";
|
|
|
|
// Induce memory fragmentation by taking down cache segments,
|
|
// which should be evicted in random order, and inducing high
|
|
// waste level in them. Should leave around up to 100M free,
|
|
// but no LSA segment should fit.
|
|
for (unsigned i = 0; i < 100 * 1024 * 1024 / (logalloc::segment_size / 2); ++i) {
|
|
stuffing.emplace_back(std::make_unique<char[]>(logalloc::segment_size / 2 + 1));
|
|
}
|
|
|
|
std::cout << "After fragmenting:\n";
|
|
std::cout << "Free memory: " << memory::stats().free_memory() << "\n";
|
|
std::cout << "Cache occupancy: " << tracker.region().occupancy() << "\n";
|
|
};
|
|
|
|
fill_cache_to_the_top();
|
|
|
|
fragment_free_space();
|
|
|
|
cache.update(*mt, checker).get();
|
|
|
|
stuffing.clear();
|
|
cache_stuffing.clear();
|
|
|
|
// Verify that all mutations from memtable went through
|
|
for (auto&& key : keys) {
|
|
auto range = query::partition_range::make_singular(key);
|
|
auto reader = cache.make_reader(range);
|
|
auto mo = reader().get0();
|
|
assert(mo);
|
|
assert(mo->partition().live_row_count(*s) ==
|
|
row_count + 1 /* one row was already in cache before update()*/);
|
|
}
|
|
|
|
std::cout << "Testing reading from cache.\n";
|
|
|
|
fill_cache_to_the_top();
|
|
|
|
for (auto&& key : keys) {
|
|
cache.touch(key);
|
|
}
|
|
|
|
for (auto&& key : keys) {
|
|
auto range = query::partition_range::make_singular(key);
|
|
auto reader = cache.make_reader(range);
|
|
auto mo = reader().get0();
|
|
assert(mo);
|
|
}
|
|
|
|
std::cout << "Testing reading when memory can't be reclaimed.\n";
|
|
// We want to check that when we really can't reserve memory, allocating_section
|
|
// throws rather than enter infinite loop.
|
|
{
|
|
stuffing.clear();
|
|
cache_stuffing.clear();
|
|
tracker.clear();
|
|
|
|
// eviction victims
|
|
for (unsigned i = 0; i < logalloc::segment_size / cell_size; ++i) {
|
|
cache.populate(make_small_mutation());
|
|
}
|
|
|
|
const mutation& m = make_large_mutation();
|
|
auto range = query::partition_range::make_singular(m.decorated_key());
|
|
|
|
cache.populate(m);
|
|
|
|
logalloc::shard_tracker().reclaim_all_free_segments();
|
|
|
|
{
|
|
logalloc::reclaim_lock _(tracker.region());
|
|
try {
|
|
while (true) {
|
|
stuffing.emplace_back(std::make_unique<char[]>(logalloc::segment_size));
|
|
}
|
|
} catch (const std::bad_alloc&) {
|
|
//expected
|
|
}
|
|
}
|
|
|
|
try {
|
|
auto reader = cache.make_reader(range);
|
|
assert(!reader().get0());
|
|
auto evicted_from_cache = logalloc::segment_size + cell_size * row_count;
|
|
new char[evicted_from_cache + logalloc::segment_size];
|
|
assert(false); // The test is not invoking the case which it's supposed to test
|
|
} catch (const std::bad_alloc&) {
|
|
// expected
|
|
}
|
|
}
|
|
});
|
|
});
|
|
}
|