Some gcc versions incorrectly complain:
tests/log_histogram_test.cc:87:22: error: ‘opts1’ is not a valid template argument for type ‘const log_histogram_options&’ because object ‘opts1’ has not external linkage
size_t hist_key<node<opts1>>(const node<opts1>& n) { return n.v; }
Apparently this is a bug in gcc:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52036Fixes#2307.
Message-Id: <1493108791-11247-1-git-send-email-tgrabiec@scylladb.com>
"This series fixes some more errors found by clang, with the aim of enabling
clang/zapcc as a supported compiler. A single issue remains, but it's
probably in std::experimental::optional::swap(); not in our code."
* tag 'clang/2/v1' of https://github.com/avikivity/scylla:
sstable_test: avoid passing negative non-type template arguments to unsigned parameters
UUID: add more comparison operators
sstable_datafile_test: avoid string_view user-defined literal conversion operator
mutation_source_test: avoid template function without template keyword
cql_query_test: define static variable
cql_query_test: add braces for single-item collection initializers
storage_service: don't use typeid(temporary)
logalloc: remove unused max_occupancy_for_compaction
storage_proxy: drop overzealous use of __int128_t in recently-modified-no-read-repair logic
storage_proxy: drop unused member access from return value
storage_proxy: fix reference bound to temporary in data_read_resolver::less_compare
read_repair_decision: fix operator<<(std::ostream&, ...)
Fixes the following error in "scylla segment-descs" and a similar one in "scylla lsa-segment":
Traceback (most recent call last):
File "scylla-gdb.py", line 530, in invoke
gdb.write('0x%x: lsa free=%d region=0x%x zone=0x%x\n' % (addr, desc['_free_space'], desc['_region'], desc['_zone']))
TypeError: %x format: an integer is required, not gdb.Value
Message-Id: <1493029465-6482-1-git-send-email-tgrabiec@scylladb.com>
Every lsa-allocated object is prefixed by a header that contains information
needed to free or migrate it. This includes its size (for freeing) and
an 8-byte migrator (for migrating). Together with some flags, the overhead
is 14 bytes (16 bytes if the default alignment is used).
This patch reduces the header size to 1 byte (8 bytes if the default alignment
is used). It uses the following techniques:
- ULEB128-like encoding (actually more like ULEB64) so a live object's header
can typically be stored using 1 byte
- indirection, so that migrators can be encoded in a small index pointing
to a migrator table, rather than using an 8-byte pointer; this exploits
the fact that only a small number of types are stored in LSA
- moving the responsibility for determining an object's size to its
migrator, rather than storing it in the header; this exploits the fact
that the migrator stores type information, and object size is in fact
information about the type
The patch improves the results of memory_footprint_test as following:
Before:
- in cache: 976
- in memtable: 947
After:
mutation footprint:
- in cache: 880
- in memtable: 858
A reduction of about 10%. Further reductions are possible by reducing the
alignment of lsa objects.
logalloc_test was adjusted to free more objects, since with the lower
footprint, rounding errors (to full segments) are different and caused
false errors to be detected.
Missing: adjustments to scylla-gdb.py; will be done after we agree on the
new descriptor's format.
We both move names_ to its destination, and call names_.size() in the same
expression; this has undefined evaluation order, and fails with clang.
With this patch as well as the clang build fixes, Scylla starts and is
able to serve requests (light cassandra-stress load).
Message-Id: <20170423121727.1948-1-avi@scylladb.com>
This patch fixes a failure of virtual_reader_test, where both the test
itself and the cql_test_env initialize the messaging_service to listen
on the same address and port, triggering an assert in
posix_ap_server_socket_impl::accept().
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Message-Id: <20170423104240.21275-1-duarte@scylladb.com>
Clang warns that the expression will be evaluated (doh). While the warning
seems dubious, keep it and change the code to call the function outside
typeid(), in case it does help someone one day.
Clang's std::abs() doesn't support __int128_t, so use __int64_t instead. With
this change, it's possible that a read repair 252,700 years after a write
will be interpreted as a recent write and the read repair will incorrectly
be skipped; hopefully by that time __int128_t will be standardized.
Argument-dependent lookup requires that the operator be declared in the
same namespace as the class; move it there.
While at it, de-static it, it only causes bloat.
"Currently, a shared sstable is rewritten at all shards it belongs to, and only
after that, it's deleted.
This new algorithm adds the ability to reshard a set of sstables together at a
single shard and produce unshared sstable for all shards involved.
That's important for the leveled compaction strategy issue, in which the number
of sstables growing considerably after resharding. What happened is that every
sstable was being split into N ones, so we could end up with tons of small
sstables. Now, we will reshard together a set of adjacent sstables."
* 'sstable_resharding_revamp_v9' of github.com:raphaelsc/scylla:
tests: add test for new sstable resharding
database: kill column_family::start_rewrite
database: wire up new resharding algorithm
database: implement new sstable resharding algorithm
database: introduce function to replace new sstables by their ancestors
prevent regular compaction from choosing shared sstables
compaction_strategy: implement resharding strategy for compaction strategies
sstables: store more info in foreign_sstable_open_info
sstables: make it possible to get open info from loaded sstable
database: export column family dir
database: inform if column family has shared tables
sstables: add method to export ancestors
lcs: implement get_level_count
compaction_manager: introduce method to check if manager stopped
lcs: restore invariant instead of sending overlapping sst to L0
sstables: extend compaction for new resharding
sstables: allow shard A to correctly create sstable for shard B
compaction: rework compacting_sstable_writer to work with multiple writers
compaction: prepare compacting_sstable_writer to work with writers
sstables: rework compaction to make it easy to extend
NOTE: it's not wired yet.
Currently, a shared sstable is rewritten at all shards it belongs
to and only after that, it's deleted. With this new algorithm, a
shared sstable will be read only once and N unshared sstables
will be created, each of them with 1/N of the data. After it's
done, each owner shard will receive its new unshared sstable
replacing its ancestors.
Another benefit is that we'll no longer have resharding resulting
in number of sstables growing considerably after resharding.
A full-sized leveled sstable is usually 160MB, so after resharding,
we could have N files of 160MB/N. Now, leveled strategy will help
resharding. N adjacent sstables of same level will be resharded
together, so we'll end up with N files of N*160MB/N.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
When resharding, we're working with sstables from all shards. So let's say
we're done with resharding of sstable A that belongs to shard 0 and 1 and
sstable B that belongs to shard 1 and 2. SStables were generated for
shards 0, 1, and 2. So shards 0, 1, and 2 need to load the new sstables
and remove the ancestors. Shard 1 for example will remove sstables A and
B (ancestors) and add the new one. Then it comes this new function.
We'll forward new sstables to their target shards using foreign sstable
open info.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
For new resharding, it's important to exclude resharding sstables
from the list of candidates for regular compaction. That's doesn't
affect current resharding because it marks the sstables as
compacting. That won't work with new resharding which will work
with sstables from multiple shards.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Strategies other than leveled will reshard one shared sstable at
a time, and the target shard, shard at which job will run, for each
job will be chosen in a round-robin fashion.
For leveled strategy, we will reshard together smp::count adjacent
sstables that belong to same level.
The reason for that is because resharding one sstable at a time
may result in creation of file for each shard, meaning after
resharding we could end up with NO_SSTABLES*NO_SHARDS.
These resharding strategies will be used for our new resharding
algorithm.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
We need that info for opening a sstable at different shard, unlike
sstable loader which has everything in entry_descriptor, obtained
from components in sstable filename.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
It will be useful for resharding which will need to move a
sstable across shards, and to do that without reloading the
sstable at target shard, we need to be able to get the open
info and move it to the target shard instead.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
That's gonna be useful to quickly determine if it's worth resharding
a column family.
Reviewed-by: Nadav Har'El <nyh@scylladb.com>
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
A large token span sstable may find its way into high level due to resharding,
which means the strategy invariant is broken. The invariant is restored by
compacting first set of overlapping sstables, meaning that the restoration
is done incrementally for multiple overlapping sets.
Invariant is restored by regular compaction after resharding puts new unshared
sstables into their original level, where level > 0.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Extends compaction for new resharding algorithm. Not wired yet.
New resharding will compact shared sstable(s) and create one
sstable for each owner. It's up to the caller to open these
new unshared sstables at their respective column families.
This new approach will save a lot of bandwidth because we'll
no longer read the entire shared sstable #smp::count times.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
That's possible by shard A explicitly saying that sstable is created
for shard B. If we don't do that, sharding metadata isn't correct,
and consequently sstable will report wrong owners.
We'll need this for resharding which will create sstables for all
shards that own the shared sstable.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
compacting_sstable_writer only allowed one writer so far, but we will need
multiple ones for resharding.
It's done by moving writer management to compaction.
finish_sstable_writer() is added for compaction impl to stop all writers,
whereas stop_sstable_writer() will only stop current writer (needed when
current sstable reaches max limit size for example).
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
No need for compacting_sstable_writer to store items that are available
in compaction class. Also, that's a step towards supporting multiple
writers for compaction.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
compact_sstables() supported both regular and cleanup compaction,
but with lots of conditions that made it ugly and hard to extend.
In the future, we want to introduce a new type of compaction for
resharding that will create one sstable for every shard owning
the sstable(s) given as input. That will be easier now.
Reviewed-by: Nadav Har'El <nyh@scylladb.com>
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
* seastar 2eec212...194d80f (4):
> removing the collectd tests
> fix fstream metrics reporting.
> do_for_each: Make it check for need preempt
> core/sharded: introduce copy method to foreign_ptr
"Currently eviction is performed until occupancy of the whole region
drops below the 85% threshold. This may take a while if region had
high occupancy and is large. We could improve the situation by only
evicting until occupancy of the sparsest segment drops below the
threshold, as is done by this change.
I tested this using a c-s read workload in which the condition
triggers in the cache region, with 1G per shard:
lsa-timing - Reclamation cycle took 12.934 us.
lsa-timing - Reclamation cycle took 47.771 us.
lsa-timing - Reclamation cycle took 125.946 us.
lsa-timing - Reclamation cycle took 144356 us.
lsa-timing - Reclamation cycle took 655.765 us.
lsa-timing - Reclamation cycle took 693.418 us.
lsa-timing - Reclamation cycle took 509.869 us.
lsa-timing - Reclamation cycle took 1139.15 us.
The 144ms pause is when large eviction is necessary.
Statistics for reclamation pauses for a read workload over
larger-than-memory data set:
Before:
avg = 865.796362
stdev = 10253.498038
min = 93.891000
max = 264078.000000
sum = 574022.988000
samples = 663
After:
avg = 513.685650
stdev = 275.270157
min = 212.286000
max = 1089.670000
sum = 340573.586000
samples = 663
Refs #1634."
* tag 'tgrabiec/lsa-reduce-reclaim-latency-v3' of github.com:cloudius-systems/seastar-dev:
lsa: Reduce reclamation latency
tests: Add test for log_histogram
log_histogram: Allow non-power-of-two minimum values
lsa: Use regular compaction threshold in on-idle compaction
tests: row_cache_test: Induce update failure more reliably
lsa: Add getter for region's eviction function
Currently eviction is performed until occupancy of the whole region
drops below the 85% threshold. This may take a while if region had
high occupancy and is large. We could improve the situation by only
evicting until occupancy of the sparsest segment drops below the
threshold, as is done by this change.
I tested this using a c-s read workload in which the condition
triggers in the cache region, with 1G per shard:
lsa-timing - Reclamation cycle took 12.934 us.
lsa-timing - Reclamation cycle took 47.771 us.
lsa-timing - Reclamation cycle took 125.946 us.
lsa-timing - Reclamation cycle took 144356 us.
lsa-timing - Reclamation cycle took 655.765 us.
lsa-timing - Reclamation cycle took 693.418 us.
lsa-timing - Reclamation cycle took 509.869 us.
lsa-timing - Reclamation cycle took 1139.15 us.
The 144ms pause is when large eviction is necessary.
Statistics for reclamation pauses for a read workload over
larger-than-memory data set:
Before:
avg = 865.796362
stdev = 10253.498038
min = 93.891000
max = 264078.000000
sum = 574022.988000
samples = 663
After:
avg = 513.685650
stdev = 275.270157
min = 212.286000
max = 1089.670000
sum = 340573.586000
samples = 663
Refs #1634.
Message-Id: <1484730859-11969-1-git-send-email-tgrabiec@scylladb.com>
We will want to reuse the min_size mechanism for the whole compaction
threshold, including the occupancy threshold. That threshold is close
to the segment size and we cannot pick a power of two which would be
close enough to what we need.
Therefore, change log_histogram to support arbitrary minimum base.
bucket_of() was moved into log_histogram_options so that it can be used
in number_of_buckets(), which makes for a simple and much less
error-prone implementation.
Idle-time compaction should not produce not-compactible segments
becuase that means we would have to evict a lot when we finally need
to reclaim some memory, so that occupancy falls below the regular
compaction threshold. This may cause latency spikes.
Refs #1634.
After changing region evicitability condition to be less strict, cache
update stopped failing because reclamation was able to compact dense
region. Induce failure by installing evictor which refuses to evict
from cache beyond few elements.
