Summary:
When a new version is created, we sort all the files at every
level based on their size. This is necessary because we want
to compact the largest file first. The sorting takes quite a
bit of CPU.
Moved the sorting code to be outside the mutex. Also, the
earlier code was sorting files at all levels but we do not
need to sort the highest-number level because those files
are never the cause of any compaction. To reduce sorting
costs, we sort only the first few files in each level
because it is likely that those are the only files in that
level that will be picked for compaction.
At steady state, I have seen that this patch increase
throughout from 1500 writes/sec to 1700 writes/sec at the
end of a 72 hour run. The cpu saving by not sorting the
last level was not distinctive in this test run because
there were only 100K files in the highest numbered level.
I expect the cpu saving to be significant when the number of
files is much higher.
This is mostly an early preview and not ready for rigorous review.
With this patch, the writs/sec is now bottlenecked not by the sorting code but by GetOverlappingInputs. I am working on a patch to optimize GetOverlappingInputs.
Test Plan: make check
Reviewers: MarkCallaghan, heyongqiang
Reviewed By: heyongqiang
Differential Revision: https://reviews.facebook.net/D6411
Summary:
Added a conditional flush in ~DBImpl to flush.
There is still a chance of writes not being persisted if there is a
crash (not a clean shutdown) before the DBImpl instance is destroyed.
Test Plan: modified db_test to meet the new expectations.
Reviewers: dhruba, heyongqiang
Differential Revision: https://reviews.facebook.net/D6519
Summary:
The default compilation process now uses "-Wall" to compile.
Fix all compilation error generated by gcc.
Test Plan: make all check
Reviewers: heyongqiang, emayanke, sheki
Reviewed By: heyongqiang
CC: MarkCallaghan
Differential Revision: https://reviews.facebook.net/D6525
Summary:
There are certain use-cases where the application intends to
delete older keys aftre they have expired a certian time period.
One option for those applications is to periodically scan the
entire database and delete appropriate keys.
A better way is to allow the application to hook into the
compaction process. This patch allows the application to set
a method callback for every key that is being compacted. If
this method returns true, then the key is not preserved in
the output of the compaction.
Test Plan:
This is mostly to preview the proposed new public api.
Since it is a public api, please do due diligence on reviewing it.
I will be writing test cases for this api in mynext version of
this patch.
Reviewers: MarkCallaghan, heyongqiang
Reviewed By: heyongqiang
CC: sheki, adsharma
Differential Revision: https://reviews.facebook.net/D6285
Summary:
as subject
Test Plan:
run db_bench and db_test
Reviewers: dhruba
Reviewed By: dhruba
Differential Revision: https://reviews.facebook.net/D6111
Summary:
This makes the stall timers in MakeRoomForWrite more accurate by timing
the sleeps. From looking at the logs the real sleep times are usually
about 2000 usecs each when SleepForMicros(1000) is called. The modified LOG messages are:
2012/10/29-12:06:33.271984 2b3cc872f700 delaying write 13 usecs for level0_slowdown_writes_trigger
2012/10/29-12:06:34.688939 2b3cc872f700 delaying write 1728 usecs for rate limits with max score 3.83
Task ID: #
Blame Rev:
Test Plan:
run db_bench, look at DB/LOG
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: dhruba
Reviewed By: dhruba
Differential Revision: https://reviews.facebook.net/D6297
Summary:
The leveldb API is enhanced to support different compression algorithms at
different levels.
This adds the option min_level_to_compress to db_bench that specifies
the minimum level for which compression should be done when
compression is enabled. This can be used to disable compression for levels
0 and 1 which are likely to suffer from stalls because of the CPU load
for memtable flushes and (L0,L1) compaction. Level 0 is special as it
gets frequent memtable flushes. Level 1 is special as it frequently
gets all:all file compactions between it and level 0. But all other levels
could be the same. For any level N where N > 1, the rate of sequential
IO for that level should be the same. The last level is the
exception because it might not be full and because files from it are
not read to compact with the next larger level.
The same amount of time will be spent doing compaction at any
level N excluding N=0, 1 or the last level. By this standard all
of those levels should use the same compression. The difference is that
the loss (using more disk space) from a faster compression algorithm
is less significant for N=2 than for N=3. So we might be willing to
trade disk space for faster write rates with no compression
for L0 and L1, snappy for L2, zlib for L3. Using a faster compression
algorithm for the mid levels also allows us to reclaim some cpu
without trading off much loss in disk space overhead.
Also note that little is to be gained by compressing levels 0 and 1. For
a 4-level tree they account for 10% of the data. For a 5-level tree they
account for 1% of the data.
With compression enabled:
* memtable flush rate is ~18MB/second
* (L0,L1) compaction rate is ~30MB/second
With compression enabled but min_level_to_compress=2
* memtable flush rate is ~320MB/second
* (L0,L1) compaction rate is ~560MB/second
This practicaly takes the same code from https://reviews.facebook.net/D6225
but makes the leveldb api more general purpose with a few additional
lines of code.
Test Plan: make check
Differential Revision: https://reviews.facebook.net/D6261
Summary:
Adds the "MB/sec in" and "MB/sec out" to this line:
Amplification: 1.7 rate, 0.01 GB in, 0.02 GB out, 8.24 MB/sec in, 13.75 MB/sec out
Changes all values to be reported per interval and since test start for this line:
... thread 0: (10000,60000) ops and (19155.6,27307.5) ops/second in (0.522041,2.197198) seconds
Task ID: #
Blame Rev:
Test Plan:
run db_bench
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: dhruba
Reviewed By: dhruba
Differential Revision: https://reviews.facebook.net/D6291
Summary:
Adds a method that returns the score for the next level that most
needs compaction. That method is then used by db_bench to rate limit threads.
Threads are put to sleep at the end of each stats interval until the score
is less than the limit. The limit is set via the --rate_limit=$double option.
The specified value must be > 1.0. Also adds the option --stats_per_interval
to enable additional metrics reported every stats interval.
Task ID: #
Blame Rev:
Test Plan:
run db_bench
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: dhruba
Reviewed By: dhruba
Differential Revision: https://reviews.facebook.net/D6243
Summary: Enable LevelDb to create a new log file if current log file is too large.
Test Plan:
Write a script and manually check the generated info LOG.
Task ID: 1803577
Blame Rev:
Reviewers: dhruba, heyongqiang
Reviewed By: heyongqiang
CC: zshao
Differential Revision: https://reviews.facebook.net/D6003
Summary:
I used server uptime to compute per-level IO throughput rates. I
intended to use time spent doing compaction at that level. This fixes that.
Task ID: #
Blame Rev:
Test Plan:
run db_bench, look at results
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: dhruba
Reviewed By: dhruba
Differential Revision: https://reviews.facebook.net/D6237
Summary:
This adds more statistics to be reported by GetProperty("leveldb.stats").
The new stats include time spent waiting on stalls in MakeRoomForWrite.
This also includes the total amplification rate where that is:
(#bytes of sequential IO during compaction) / (#bytes from Put)
This also includes a lot more data for the per-level compaction report.
* Rn(MB) - MB read from level N during compaction between levels N and N+1
* Rnp1(MB) - MB read from level N+1 during compaction between levels N and N+1
* Wnew(MB) - new data written to the level during compaction
* Amplify - ( Write(MB) + Rnp1(MB) ) / Rn(MB)
* Rn - files read from level N during compaction between levels N and N+1
* Rnp1 - files read from level N+1 during compaction between levels N and N+1
* Wnp1 - files written to level N+1 during compaction between levels N and N+1
* NewW - new files written to level N+1 during compaction
* Count - number of compactions done for this level
This is the new output from DB::GetProperty("leveldb.stats"). The old output stopped at Write(MB)
Compactions
Level Files Size(MB) Time(sec) Read(MB) Write(MB) Rn(MB) Rnp1(MB) Wnew(MB) Amplify Read(MB/s) Write(MB/s) Rn Rnp1 Wnp1 NewW Count
-------------------------------------------------------------------------------------------------------------------------------------
0 3 6 33 0 576 0 0 576 -1.0 0.0 1.3 0 0 0 0 290
1 127 242 351 5316 5314 570 4747 567 17.0 12.1 12.1 287 2399 2685 286 32
2 161 328 54 822 824 326 496 328 4.0 1.9 1.9 160 251 411 160 161
Amplification: 22.3 rate, 0.56 GB in, 12.55 GB out
Uptime(secs): 439.8
Stalls(secs): 206.938 level0_slowdown, 0.000 level0_numfiles, 24.129 memtable_compaction
Task ID: #
Blame Rev:
Test Plan:
run db_bench
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
(cherry picked from commit ecdeead38f86cc02e754d0032600742c4f02fec8)
Reviewers: dhruba
Differential Revision: https://reviews.facebook.net/D6153
Summary:
The compaction process deletes a large number of files. This takes
quite a bit of time and is best done outside the mutex lock.
Test Plan: make check
Differential Revision: https://reviews.facebook.net/D6123
Summary:
The compaction process deletes a large number of files. This takes
quite a bit of time and is best done outside the mutex lock.
Test Plan: make check
Differential Revision: https://reviews.facebook.net/D6123
Summary:
The compaction process deletes a large number of files. This takes
quite a bit of time and is best done outside the mutex lock.
Test Plan:
Reviewers:
CC:
Task ID: #
Blame Rev:
published in https://reviews.facebook.net/D5997.
Summary:
This patch allows compaction to occur in multiple background threads
concurrently.
If a manual compaction is issued, the system falls back to a
single-compaction-thread model. This is done to ensure correctess
and simplicity of code. When the manual compaction is finished,
the system resumes its concurrent-compaction mode automatically.
The updates to the manifest are done via group-commit approach.
Test Plan: run db_bench
Summary:
The method DeleteObsolete files is a very costly methind, especially
when the number of files in a system is large. It makes a list of
all live-files and then scans the directory to compute the diff.
By default, this method is executed after every compaction run.
This patch makes it such that DeleteObsolete files is never
invoked twice within a configured period.
Test Plan: run all unit tests
Reviewers: heyongqiang, MarkCallaghan
Reviewed By: MarkCallaghan
Differential Revision: https://reviews.facebook.net/D6045
Summary:
If ReadCompaction is switched off, then it is better to not even
submit background compaction jobs. I see about 3% increase in
read-throughput on a pure memory database.
Test Plan: run db_bench
Reviewers: heyongqiang
Reviewed By: heyongqiang
Differential Revision: https://reviews.facebook.net/D5673
Summary: Print out the compile version in the LOG.
Test Plan: run dbbench and verify LOG
Reviewers: heyongqiang
Reviewed By: heyongqiang
Differential Revision: https://reviews.facebook.net/D5529
Summary:
A set of apis that allows an application to backup data from the
leveldb database based on a set of files.
Test Plan: unint test attached. more coming soon.
Reviewers: heyongqiang
Reviewed By: heyongqiang
Differential Revision: https://reviews.facebook.net/D5439
Summary: added a new option db_log_dir, which points the log dir. Inside that dir, in order to make log names unique, the log file name is prefixed with the leveldb data dir absolute path.
Test Plan: db_test
Reviewers: dhruba
Reviewed By: dhruba
Differential Revision: https://reviews.facebook.net/D5205
Summary:
Clean up compiler warnings generated by -Wall option.
make clean all OPT=-Wall
This is a pre-requisite before making a new release.
Test Plan: compile and run unit tests
Reviewers: heyongqiang
Reviewed By: heyongqiang
Differential Revision: https://reviews.facebook.net/D5019
Summary: as subject. ported the change from google code leveldb 1.5
Test Plan: run db_test
Reviewers: dhruba
Differential Revision: https://reviews.facebook.net/D4839
Summary:
Introduce a new method Env->Fsync() that issues fsync (instead of fdatasync).
This is needed for data durability when running on ext3 filesystems.
Added options to the benchmark db_bench to generate performance numbers
with either fsync or fdatasync enabled.
Cleaned up Makefile to build leveldb_shell only when building the thrift
leveldb server.
Test Plan: build and run benchmark
Reviewers: heyongqiang
Reviewed By: heyongqiang
Differential Revision: https://reviews.facebook.net/D4911
Summary: Log the open-options to the LOG. Use options_ instead of options because SanitizeOptions could modify the max_file_open limit.
Test Plan: num db_bench
Reviewers: heyongqiang
Reviewed By: heyongqiang
Differential Revision: https://reviews.facebook.net/D4833
Summary:
Fixed unit test c_test by initializing logger=NULL.
Removed "atomic" from last_log_ts so that unit tests do not require C11 compiler.
Anyway, last_log_ts is mostly used for logging, so it is ok if it is loosely
accurate.
Test Plan: run c_test
Reviewers: heyongqiang
Reviewed By: heyongqiang
Differential Revision: https://reviews.facebook.net/D4803
Summary: Record the version of the source that we are compiling. We keep a record of the git revision in util/version.cc. This source file is then built as a regular source file as part of the compilation process. One can run "strings executable_filename | grep _build_" to find the version of the source that we used to build the executable file.
Test Plan: none
Differential Revision: https://reviews.facebook.net/D4785
Summary:
as subject.
A new log is written to scribe via thrift client when a new db is opened and when there is
a compaction.
a new option var scribe_log_db_stats is added.
Test Plan: manually checked using command "ptail -time 0 leveldb_deploy_stats"
Reviewers: dhruba
Differential Revision: https://reviews.facebook.net/D4659
Summary: as subject and only maintain 10 log files.
Test Plan: new test in db_test
Reviewers: dhruba
Differential Revision: https://reviews.facebook.net/D4731
Summary: as subject. The flush will flush everything in the db.
Test Plan: new test in db_test.cc
Reviewers: dhruba
Reviewed By: dhruba
Differential Revision: https://reviews.facebook.net/D4029
Summary:
Added option --writes=xxx to specify the number of keys that we want to overwrite in the benchmark.
Task ID: #
Blame Rev:
Test Plan: Revert Plan:
Reviewers: adsharma
CC: sc
Differential Revision: https://reviews.facebook.net/D3465
In particular, we add a new FilterPolicy class. An instance
of this class can be supplied in Options when opening a
database. If supplied, the instance is used to generate
summaries of keys (e.g., a bloom filter) which are placed in
sstables. These summaries are consulted by DB::Get() so we
can avoid reading sstable blocks that are guaranteed to not
contain the key we are looking for.
This change provides one implementation of FilterPolicy
based on bloom filters.
Other changes:
- Updated version number to 1.4.
- Some build tweaks.
- C binding for CompactRange.
- A few more benchmarks: deleteseq, deleterandom, readmissing, seekrandom.
- Minor .gitignore update.
- Replace raw slice comparison with a call to user comparator.
Added test for custom comparators.
- Fix end of namespace comments.
- Fixed bug in picking inputs for a level-0 compaction.
When finding overlapping files, the covered range may expand
as files are added to the input set. We now correctly expand
the range when this happens instead of continuing to use the
old range. For example, suppose L0 contains files with the
following ranges:
F1: a .. d
F2: c .. g
F3: f .. j
and the initial compaction target is F3. We used to search
for range f..j which yielded {F2,F3}. However we now expand
the range as soon as another file is added. In this case,
when F2 is added, we expand the range to c..j and restart the
search. That picks up file F1 as well.
This change fixes a bug related to deleted keys showing up
incorrectly after a compaction as described in Issue 44.
(Sync with upstream @25072954)
- Added DB::CompactRange() method.
Changed manual compaction code so it breaks up compactions of
big ranges into smaller compactions.
Changed the code that pushes the output of memtable compactions
to higher levels to obey the grandparent constraint: i.e., we
must never have a single file in level L that overlaps too
much data in level L+1 (to avoid very expensive L-1 compactions).
Added code to pretty-print internal keys.
- Fixed bug where we would not detect overlap with files in
level-0 because we were incorrectly using binary search
on an array of files with overlapping ranges.
Added "leveldb.sstables" property that can be used to dump
all of the sstables and ranges that make up the db state.
- Removing post_write_snapshot support. Email to leveldb mailing
list brought up no users, just confusion from one person about
what it meant.
- Fixing static_cast char to unsigned on BIG_ENDIAN platforms.
Fixes Issue 35 and Issue 36.
- Comment clarification to address leveldb Issue 37.
- Change license in posix_logger.h to match other files.
- A build problem where uint32 was used instead of uint32_t.
Sync with upstream @24408625
- Fix bug in Get: when it triggers a compaction, it could sometimes
mark the compaction with the wrong level (if there was a gap
in the set of levels examined for the Get).
- Do not hold mutex while writing to the log file or to the
MANIFEST file.
Added a new benchmark that runs a writer thread concurrently with
reader threads.
Percentiles
------------------------------
micros/op: avg median 99 99.9 99.99 99.999 max
------------------------------------------------------
before: 42 38 110 225 32000 42000 48000
after: 24 20 55 65 130 1100 7000
- Fixed race in optimized Get. It should have been using the
pinned memtables, not the current memtables.
git-svn-id: https://leveldb.googlecode.com/svn/trunk@50 62dab493-f737-651d-591e-8d6aee1b9529
- Fix for issue 33 (non-null-terminated result from
leveldb_property_value())
- Support for running multiple instances of a benchmark in parallel.
- Reduce lock contention on Get():
(1) Do not hold the lock while searching memtables.
(2) Shard block and table caches 16-ways.
Benchmark for evaluating this change:
$ db_bench --benchmarks=fillseq1,readrandom --threads=$n
(fillseq1 is a small hack to make sure fillseq runs once regardless
of number of threads specified on the command line).
git-svn-id: https://leveldb.googlecode.com/svn/trunk@49 62dab493-f737-651d-591e-8d6aee1b9529
- Removed one copy of an uncompressed block contents changing
the signature of Snappy_Uncompress() so it uncompresses into a
flat array instead of a std::string.
Speeds up readrandom ~10%.
- Instead of a combination of Env/WritableFile, we now have a
Logger interface that can be easily overridden applications
that want to supply their own logging.
- Separated out the gcc and Sun Studio parts of atomic_pointer.h
so we can use 'asm', 'volatile' keywords for Sun Studio.
git-svn-id: https://leveldb.googlecode.com/svn/trunk@39 62dab493-f737-651d-591e-8d6aee1b9529
Slight tweak to the no-overlap optimization: only push to
level 2 to reduce the amount of wasted space when the same
small key range is being repeatedly overwritten.
Fix for Issue 18: Avoid failure on Windows by avoiding
deletion of lock file until the end of DestroyDB().
Fix for Issue 19: Disregard sequence numbers when checking for
overlap in sstable ranges. This fixes issue 19: when writing
the same key over and over again, we would generate a sequence
of sstables that were never merged together since their sequence
numbers were disjoint.
Don't ignore map/unmap error checks.
Miscellaneous fixes for small problems Sanjay found while diagnosing
issue/9 and issue/16 (corruption_testr failures).
- log::Reader reports the record type when it finds an unexpected type.
- log::Reader no longer reports an error when it encounters an expected
zero record regardless of the setting of the "checksum" flag.
- Added a missing forward declaration.
- Documented a side-effects of larger write buffer sizes
(longer recovery time).
git-svn-id: https://leveldb.googlecode.com/svn/trunk@37 62dab493-f737-651d-591e-8d6aee1b9529
- Implemented Get() directly instead of building on top of a full
merging iterator stack. This speeds up the "readrandom" benchmark
by up to 15-30%.
- Fixed an opensource compilation problem.
Added --db=<name> flag to control where the database is placed.
- Automatically compact a file when we have done enough
overlapping seeks to that file.
- Fixed a performance bug where we would read from at least one
file in a level even if none of the files overlapped the key
being read.
- Makefile fix for Mac OSX installations that have XCode 4 without XCode 3.
- Unified the two occurrences of binary search in a file-list
into one routine.
- Found and fixed a bug where we would unnecessarily search the
last file when looking for a key larger than all data in the
level.
- A fix to avoid the need for trivial move compactions and
therefore gets rid of two out of five syncs in "fillseq".
- Removed the MANIFEST file write when switching to a new
memtable/log-file for a 10-20% improvement on fill speed on ext4.
- Adding a SNAPPY setting in the Makefile for folks who have
Snappy installed. Snappy compresses values and speeds up writes.
git-svn-id: https://leveldb.googlecode.com/svn/trunk@32 62dab493-f737-651d-591e-8d6aee1b9529
Fixed race condition reported by Dave Smit (dizzyd@dizzyd,com)
on the leveldb mailing list. We were not signalling
waiters after a trivial move from level-0. The result was
that in some cases (hard to reproduce), a write would get
stuck forever waiting for the number of level-0 files to drop
below its hard limit.
The new code is simpler: there is just one condition variable
instead of two, and the condition variable is signalled after
every piece of background work finishes. Also, all compaction
work (including for manual compactions) is done in the
background thread, and therefore we can remove the
"compacting_" variable.
git-svn-id: https://leveldb.googlecode.com/svn/trunk@31 62dab493-f737-651d-591e-8d6aee1b9529
* Patch LevelDB to build for OSX and iOS
* Fix race condition in memtable iterator deletion.
* Other small fixes.
git-svn-id: https://leveldb.googlecode.com/svn/trunk@29 62dab493-f737-651d-591e-8d6aee1b9529
* env_chromium.cc should not export symbols.
* Fix MSVC warnings.
* Removed large value support.
* Fix broken reference to documentation file
git-svn-id: https://leveldb.googlecode.com/svn/trunk@24 62dab493-f737-651d-591e-8d6aee1b9529
