Hi, arg sorry i got it. Building the test right now. Will report results shortly. Greets, Stefan Am 04.11.2017 um 21:10 schrieb Sage Weil: > On Sat, 4 Nov 2017, Stefan Priebe - Profihost AG wrote: >> Hi Sage, >> >> Am 26.10.2017 um 13:58 schrieb Sage Weil: >>> On Thu, 26 Oct 2017, Stefan Priebe - Profihost AG wrote: >>>> Hi Sage, >>>> >>>> Am 25.10.2017 um 21:54 schrieb Sage Weil: >>>>> On Wed, 25 Oct 2017, Stefan Priebe - Profihost AG wrote: >>>>>> Hello, >>>>>> >>>>>> in the lumious release notes is stated that zstd is not supported by >>>>>> bluestor due to performance reason. I'm wondering why btrfs instead >>>>>> states that zstd is as fast as lz4 but compresses as good as zlib. >>>>>> >>>>>> Why is zlib than supported by bluestor? And why does btrfs / facebook >>>>>> behave different? >>>>>> >>>>>> "BlueStore supports inline compression using zlib, snappy, or LZ4. (Ceph >>>>>> also supports zstd for RGW compression but zstd is not recommended for >>>>>> BlueStore for performance reasons.)" >>>>> >>>>> zstd will work but in our testing the performance wasn't great for >>>>> bluestore in particular. The problem was that for each compression run >>>>> there is a relatively high start-up cost initializing the zstd >>>>> context/state (IIRC a memset of a huge memory buffer) that dominated the >>>>> execution time... primarily because bluestore is generally compressing >>>>> pretty small chunks of data at a time, not big buffers or streams. >>>>> >>>>> Take a look at unittest_compression timings on compressing 16KB buffers >>>>> (smaller than bluestore needs usually, but illustrated of the problem): >>>>> >>>>> [ RUN ] Compressor/CompressorTest.compress_16384/0 >>>>> [plugin zlib (zlib/isal)] >>>>> [ OK ] Compressor/CompressorTest.compress_16384/0 (294 ms) >>>>> [ RUN ] Compressor/CompressorTest.compress_16384/1 >>>>> [plugin zlib (zlib/noisal)] >>>>> [ OK ] Compressor/CompressorTest.compress_16384/1 (1755 ms) >>>>> [ RUN ] Compressor/CompressorTest.compress_16384/2 >>>>> [plugin snappy (snappy)] >>>>> [ OK ] Compressor/CompressorTest.compress_16384/2 (169 ms) >>>>> [ RUN ] Compressor/CompressorTest.compress_16384/3 >>>>> [plugin zstd (zstd)] >>>>> [ OK ] Compressor/CompressorTest.compress_16384/3 (4528 ms) >>>>> >>>>> It's an order of magnitude slower than zlib or snappy, which probably >>>>> isn't acceptable--even if it is a bit smaller. >> >> i've fixed the zstd compression plugin to use reset stream instead of >> initializing new objects. >> >> What's needed to run only / just the unittest_compression test? > > make unittest_compression && bin/unittest_compression > > should do it! > > sage > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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