Thanks Adam. Don't get too scared :) Ignore the commit history and just look at github's "Files changed" tab, the modification summary is:
"Showing 19 changed files with 730 additions and 402 deletions." More than half of those commits were merges with trunk, many snappy refactorings (before it was added to trunk) and other experiments that were reverted after. We'll try to break this into 2 or 3 patches. So the single patch is something relatively small: https://github.com/fdmanana/couchdb/compare/async_file_writes_no_test.diff On Fri, Jun 24, 2011 at 4:05 AM, Adam Kocoloski <[email protected]> wrote: > Hi Damien, I'd like to see these 220 commits rebased into a set of logical > patches against trunk. It'll make the review easier and will help future > devs track down any bugs that are introduced. Best, > > Adam > > On Jun 23, 2011, at 6:49 PM, Damien Katz wrote: > >> Hi everyone, >> >> As it’s known by many of you, Filipe and I have been working on improving >> performance, specially write performance [1]. This work has been public in >> the Couchbase github account since the beginning, and the non Couchbase >> specific changes are now isolated in [2] and [3]. >> In [3] there’s an Erlang module that is used to test the performance when >> writing and updating batches of documents with concurrency, which was used, >> amongst other tools, to measure the performance gains. This module bypasses >> the network stack and the JSON parsing, so that basically it allows us to >> see more easily how significant the changes in couch_file, couch_db and >> couch_db_updater are. >> >> The main and most important change is asynchronous writes. The file module >> no longer blocks callers until the write calls complete. Instead they >> immediately reply to the caller with the position in the file where the data >> is going to be written to. The data is then sent to a dedicated loop process >> that is continuously writing the data it receives, from the couch_file >> gen_server, to disk (and batching when possible). This allows callers (such >> as the db updater for.e.g.) to issue write calls and keep doing other work >> (preparing documents, etc) while the writes are being done in parallel. >> After issuing all the writes, callers simply call the new ‘flush’ function >> in the couch_file gen_server, which will block the caller until everything >> was effectively written to disk - normally this flush call ends up not >> blocking the caller or it blocks it for a very small period. >> >> There are other changes such as avoiding 2 btree lookups per document ID >> (COUCHDB-1084 [4]), faster sorting in the updater (O(n log n) vs O(n^2)) and >> avoid sorting already sorted lists in the updater. >> >> Checking if attachments are compressible was also moved into a new >> module/process. We verified this took much CPU time when all or most of the >> documents to write/update have attachments - building the regexps and >> matching against them for every single attachment is surprisingly expensive. >> >> There’s also a new couch_db:update_doc/s flag named ‘optimistic’ which >> basically changes the behaviour to write the document bodies before entering >> the updater and skip some attachment related checks (duplicated names for >> e.g.). This flag is not yet exposed to the HTTP api, but it could be via an >> X-Optimistic-Write header in the doc PUT/POST requests and _bulk_docs for >> e.g. We’ve seen this as good when the client knows that the documents to >> write don’t exist yet in the database and we aren’t already IO bound, such >> as when SSDs are used. >> >> We used relaximation, Filipe’s basho bench based tests [5] and the Erlang >> test module mentioned before [6, 7], exposed via the HTTP . Here follow some >> benchmark results. >> >> >> # Using the Erlang test module (test output) >> >> ## 1Kb documents, 10 concurrent writers, batches of 500 docs >> >> trunk before snappy was added: >> >> {"db":"load_test","total":100000,"batch":500,"concurrency":10,"rounds":10,"delayed_commits":false,"optimistic":false,"total_time_ms":270071} >> >> trunk: >> >> {"db":"load_test","total":100000,"batch":500,"concurrency":10,"rounds":10,"delayed_commits":false,"optimistic":false,"total_time_ms":157328} >> >> trunk + async writes (and snappy): >> >> {"db":"load_test","total":100000,"batch":500,"concurrency":10,"rounds":10,"delayed_commits":false,"optimistic":false,"total_time_ms":121518} >> >> ## 2.5Kb documents, 10 concurrent writers, batches of 500 docs >> >> trunk before snappy was added: >> >> {"db":"load_test","total":100000,"batch":500,"concurrency":10,"rounds":10,"delayed_commits":false,"optimistic":false,"total_time_ms":507098} >> >> trunk: >> >> {"db":"load_test","total":100000,"batch":500,"concurrency":10,"rounds":10,"delayed_commits":false,"optimistic":false,"total_time_ms":230391} >> >> trunk + async writes (and snappy): >> >> {"db":"load_test","total":100000,"batch":500,"concurrency":10,"rounds":10,"delayed_commits":false,"optimistic":false,"total_time_ms":190151} >> >> >> # bash bench tests, via the public HTTP APIs >> >> ## batches of 1 1Kb docs, 50 writers, 5 minutes run >> >> trunk: 147 702 docs written >> branch: 149 534 docs written >> >> ## batches of 10 1Kb docs, 50 writers, 5 minutes run >> >> trunk: 878 520 docs written >> branch: 991 330 docs written >> >> ## batches of 100 1Kb docs, 50 writers, 5 minutes run >> >> trunk: 1 627 600 docs written >> branch: 1 865 800 docs written >> >> ## batches of 1 2.5Kb docs, 50 writers, 5 minutes run >> >> trunk: 142 531 docs written >> branch: 143 012 docs written >> >> ## batches of 10 2.5Kb docs, 50 writers, 5 minutes run >> >> trunk: 724 880 docs written >> branch: 780 690 docs written >> >> ## batches of 100 2.5Kb docs, 50 writers, 5 minutes run >> >> trunk: 1 028 600 docs written >> branch: 1 152 800 docs written >> >> >> # bash bench tests, via the internal Erlang APIs >> ## batches of 100 2.5Kb docs, 50 writers, 5 minutes run >> >> trunk: 3 170 100 docs written >> branch: 3 359 900 docs written >> >> >> # Relaximation tests >> >> 1Kb docs: >> >> http://graphs.mikeal.couchone.com/#/graph/4843dbdf8fa104783870094b83002a1a >> >> 2.5Kb docs: >> >> http://graphs.mikeal.couchone.com/#/graph/4843dbdf8fa104783870094b830022c0 >> >> 4Kb docs: >> >> http://graphs.mikeal.couchone.com/#/graph/4843dbdf8fa104783870094b8300330d >> >> >> All the documents used for these tests can be found at: >> https://github.com/fdmanana/basho_bench_couch/tree/master/couch_docs >> >> >> Now some view indexing tests. >> >> # indexer_test_2 database >> (http://fdmanana.couchone.com/_utils/database.html?indexer_test_2) >> >> ## trunk >> >> $ time curl >> http://localhost:5984/indexer_test_2/_design/test/_view/view1?limit=1 >> {"total_rows":1102400,"offset":0,"rows":[ >> {"id":"00d49881-7bcf-4c3d-a65d-e44435eeb513","key":["dwarf","assassin",2,1.1],"value":[{"x":174347.18,"y":127272.8},{"x":35179.93,"y":41550.55},{"x":157014.38,"y":172052.63},{"x":116185.83,"y":69871.73},{"x":153746.28,"y":190006.59}]} >> ]} >> >> real 20m51.388s >> user 0m0.040s >> sys 0m0.000s >> >> >> ## branch async writes >> >> $ time curl >> http://localhost:5984/indexer_test_2/_design/test/_view/view1?limit=1 >> {"total_rows":1102400,"offset":0,"rows":[ >> {"id":"00d49881-7bcf-4c3d-a65d-e44435eeb513","key":["dwarf","assassin",2,1.1],"value":[{"x":174347.18,"y":127272.8},{"x":35179.93,"y":41550.55},{"x":157014.38,"y":172052.63},{"x":116185.83,"y":69871.73},{"x":153746.28,"y":190006.59}]} >> ]} >> >> real 15m17.908s >> user 0m0.008s >> sys 0m0.020s >> >> >> # indexer_test_3_database >> (http://fdmanana.couchone.com/_utils/database.html?indexer_test_3) >> >> ## trunk >> >> $ time curl >> http://localhost:5984/indexer_test_3/_design/test/_view/view1?limit=1 >> {"total_rows":1102400,"offset":0,"rows":[ >> {"id":"00d49881-7bcf-4c3d-a65d-e44435eeb513","key":["dwarf","assassin",2,1.1],"value":[{"x":174347.18,"y":127272.8},{"x":35179.93,"y":41550.55},{"x":157014.38,"y":172052.63},{"x":116185.83,"y":69871.73},{"x":153746.28,"y":190006.59}]} >> ]} >> >> real 21m17.346s >> user 0m0.012s >> sys 0m0.028s >> >> ## branch async writes >> >> $ time curl >> http://localhost:5984/indexer_test_3/_design/test/_view/view1?limit=1 >> {"total_rows":1102400,"offset":0,"rows":[ >> {"id":"00d49881-7bcf-4c3d-a65d-e44435eeb513","key":["dwarf","assassin",2,1.1],"value":[{"x":174347.18,"y":127272.8},{"x":35179.93,"y":41550.55},{"x":157014.38,"y":172052.63},{"x":116185.83,"y":69871.73},{"x":153746.28,"y":190006.59}]} >> ]} >> >> real 16m28.558s >> user 0m0.012s >> sys 0m0.020s >> >> We don’t show nearly as big of improvements for single write per request >> benchmarks as we do with bulk writes. This is due to the HTTP request >> overhead and our own inefficiencies at that layer. We have lots of room yet >> for optimizations at the networking layer. >> >> We'd like to merge this code into trunk next week by next wednesday. Please >> respond with any improvement, objections or comments by then. Thanks! >> >> -Damien >> >> >> [1] - >> http://blog.couchbase.com/driving-performance-improvements-couchbase-single-server-two-dot-zero >> [2] - https://github.com/fdmanana/couchdb/compare/async_file_writes_no_test >> [3] - https://github.com/fdmanana/couchdb/compare/async_file_writes >> [4] - https://issues.apache.org/jira/browse/COUCHDB-1084 >> [5] - https://github.com/fdmanana/basho_bench_couch >> [6] - https://github.com/fdmanana/couchdb/blob/async_file_writes/gen_load.sh >> [7] - >> https://github.com/fdmanana/couchdb/blob/async_file_writes/src/couchdb/couch_internal_load_gen.erl > > -- Filipe David Manana, [email protected], [email protected] "Reasonable men adapt themselves to the world. Unreasonable men adapt the world to themselves. That's why all progress depends on unreasonable men."
