Hi, Juan I'll read the series soon. Thanks for sending that to me!
Denis On 24.01.2020 15:43, Juan Quintela wrote: > Denis Plotnikov <dplotni...@virtuozzo.com> wrote: >> zstd date compression algorithm shows better performance on data compression. >> It might be useful to employ the algorithm in VM migration to reduce CPU >> usage. >> A user will be able to choose between those algorithms, therefor >> compress-type >> migration parameter is added. >> >> Here are some results of performance comparison zstd vs gzip: > Please, could you comment on the series: > > [PATCH v3 00/21] Multifd Migration Compression > > That series integrated zstd/zlib compression on top of multifd, > advantages over "old" compression code are: > - We don't have to copy data back and forth > - The unit of compression is 512KB instead of 4kb > - We "conserve" the compression state between packets (this is specially > interesting for zstd, that uses dictionaries) > >> host: i7-4790 8xCPU @ 3.60GHz, 16G RAM >> migration to the same host >> VM: 2xVCPU, 8G RAM total >> 5G RAM used, memory populated with postgreqsl data >> produced by pgbench performance benchmark >> >> >> Threads: 1 compress – 1 decompress >> >> zstd provides slightly less compression ratio with almost the same >> CPU usage but copes with RAM compression roghly 2 times faster >> >> compression type zlib | zstd >> --------------------------------------------------------- >> compression level 1 5 | 1 5 >> compression ratio 6.92 7.05 | 6.69 6.89 >> cpu idle, % 82 83 | 86 80 >> time, sec 49 71 | 26 31 >> time diff to zlib, sec -25 -41 >> >> >> Threads: 8 compress – 2 decompress >> >> zstd provides the same migration time with less cpu consumption >> >> compression type none | gzip(zlib) | zstd >> ------------------------------------------------------------------------------ >> compression level - | 1 5 9 | 1 5 15 >> compression ratio - | 6.94 6.99 7.14 | 6.64 6.89 >> 6.93 >> time, sec 154 | 22 23 27 | 23 23 25 >> cpu idle, % 99 | 45 30 12 | 70 52 23 >> cpu idle diff to zlib | | -25% -22% -11% > I don't have handy results, but it looked for me like you: > - zstd has a way better latency than zlib (i.e. the packet cames sooner) > - And it compress much better > > On the migration test (best possible case for a compressor, as we are > writting just one byte of each page, and we write the same value in all > pages): > > - zlib: compress 512KB -> 2500 bytes > - zstd: compess 512KB -> 52 bytes (yeap, I tested several times, it > looked too small) > > See that I posted another patch to "delete" the old compression code. > Why? > - I have been unable to modify migration-test to test it and work > reliablely (only way was to allow a really huge downtime) > - Even with slow networking (1Gigabit) I got really mixed results, > because as it is so slow, the guest continue dirtying memory, and in > my tests it was never a winner > > Thanks, Juan. >
