Actually, I'm concerned about the correctness of benchmark using MemStore. AFAR it may cause lots of memory frag and cause performance degraded hugely. Maybe set "filestore_blackhole=true" is more precious? On Fri, Feb 20, 2015 at 5:49 PM, Blair Bethwaite <blair.bethwaite@xxxxxxxxx> wrote: > Hi James, > > Interesting results, but did you do any tests with a NUMA system? IIUC > the original report was from a dual socket setup, and that'd > presumably be the standard setup for most folks (both OSD server and > client side). > > Cheers, > > On 20 February 2015 at 20:07, James Page <james.page@xxxxxxxxxx> wrote: >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA256 >> >> Hi All >> >> The Ubuntu Kernel team have spent the last few weeks investigating the >> apparent performance disparity between RHEL 7 and Ubuntu 14.04; we've >> focussed efforts in a few ways (see below). >> >> All testing has been done using the latest Firefly release. >> >> 1) Base network latency >> >> Jay Vosburgh looked at the base network latencies between RHEL 7 and >> Ubuntu 14.04; under default install, RHEL actually had slightly worse >> latency than Ubuntu due to the default enablement of a firewall; >> disabling this brought latency back inline between the two distributions: >> >> OS rtt min/avg/max/mdev >> Ubuntu 14.04 (3.13) 0.013/0.016/0.018/0.005 ms >> RHEL7 (3.10) 0.010/0.018/0.025/0.005 ms >> >> ...base network latency is pretty much the same. >> >> This testing was performed on a matched pair of Dell Poweredge R610's, >> configured with a single 4 core CPU and 8G of RAM. >> >> 2) Latency and performance in Ceph using Rados bench >> >> Colin King spent a number of days testing and analysing results using >> rados bench against a single node ceph deployment, configured with a >> single memory backed OSD, to see if we could reproduce the disparities >> reported. >> >> He ran 120 second OSD benchmarks on RHEL 7 as well as Ubuntu 14.04 LTS >> with a selection of kernels including 3.10 vanilla, 3.13.0-44 (release >> kernel), 3.16.0-30 (utopic HWE kernel), 3.18.0-12 (vivid HWE kernel) >> and 3.19-rc6 with 1, 16 and 128 client threads. The data collected is >> available at [0]. >> >> Each round of tests consisted of 15 runs, from which we computed >> average latency, latency deviation and latency distribution: >> >>> 120 second x 1 thread >> >> Results all seem to cluster around 0.04->0.05ms, with RHEL 7 averaging >> at 0.044 and recent Ubuntu kernels at 0.036-0.037ms. The older 3.10 >> kernel in RHEL 7 does have some slightly higher average latency. >> >>> 120 second x 16 threads >> >> Results all seem to cluster around 0.6-0.7ms. 3.19.0-rc6 had a couple >> of 1.4ms outliers which pushed it out to be worse than RHEL 7. On the >> whole Ubuntu 3.10-3.18 kernels are better than RHEL 7 by ~0.1ms. RHEL >> shows a far higher standard deviation, due to the bimodal latency >> distribution, which from the casual observer may appear to be more >> "jittery". >> >>> 120 second x 128 threads >> >> Later kernels show up to have less standard deviation than RHEL 7, so >> that shows perhaps less jitter in the stats than RHEL 7's 3.10 kernel. >> With this many threads pounding the test, we get a wider spread of >> latencies and it is hard to tell any kind of latency distribution >> patterns with just 15 rounds because of the large amount of latency >> jitter. All systems show a latency of ~ 5ms. Taking into >> consideration the amount of jitter, we think these results do not make >> much sense unless we repeat these tests with say 100 samples. >> >> 3) Conclusion >> >> We’ve have not been able to show any major anomalies in Ceph on Ubuntu >> compared to RHEL 7 when using memstore. Our current hypothesis is that >> one needs to run the OSD bench stressor many times to get a fair capture >> of system latency stats. The reason for this is: >> >> * Latencies are very low with memstore, so any small jitter in >> scheduling etc will show up as a large distortion (as shown by the large >> standard deviations in the samples). >> >> * When memstore is heavily utilized, memory pressure causes the system >> to page heavily and so we are subject to the nature of perhaps delays on >> paging that cause some latency jitters. Latency differences may be just >> down to where a random page is in memory or in swap, and with memstore >> these may cause the large perturbations we see when running just a >> single test. >> >> * We needed to make *many* tens of measurements to get a typical idea of >> average latency and the latency distributions. Don't trust the results >> from just one test >> >> * We ran the tests with a pool configured to 100 pgs and 100 pgps [1]. >> One can get different results with different placement group configs. >> >> I've CC'ed both Colin and Jay on this mail - so if anyone has any >> specific questions about the testing they can chime in with responses. >> >> Regards >> >> James >> >> [0] http://kernel.ubuntu.com/~cking/.ceph/ceph-benchmarks.ods >> [1] http://ceph.com/docs/master/rados/configuration/pool-pg-config-ref/ >> >> - -- >> James Page >> Ubuntu and Debian Developer >> james.page@xxxxxxxxxx >> jamespage@xxxxxxxxxx >> -----BEGIN PGP SIGNATURE----- >> Version: GnuPG v1 >> >> iQIcBAEBCAAGBQJU5vlrAAoJEL/srsug59jDMvAQAIhSR4GFTXNc4RLpHtLT6h/X >> K5uyauKZGtL+wqtPKRfsXqbbUw9I5AZDifQuOEJ0APccLIPbgqxEN3d2uht/qygH >> G8q2Ax+M8OyZz07yqTitnD4JV3RmL8wNHUveWPLV0gs2TzBBYwP1ywExbRPed3PY >> cfDrszgkQszA/JwT5W5YNf1LZc+5VpOEFrTiLIaRzUDoxg7mm6Hwr3XT8OFjZhjm >> LSenKREHtrKKWoBh+OKTvuCUnHzEemK+CiwwRbNQ8l7xbp71wLyS08NpSB5C1y70 >> 7uft+kP6XOGE9AKLvsdEL1PIXHfeKNonBEN5mO6nsXIW+MQzou01zHgDtne7AxDA >> 5OebQJfJtArmKt78WHuVg7h8gPcIRTRSW43LqJiADnIHL8fnZxj2v5yDiUQj7isw >> nYWXEJ3rR7mlVgydN34KQ7gpVWmGjhrVb8N01+zYOMAaTBnekldHdueEAXR07eU0 >> PXiP9aOZiAxbEnDiJmreehjCuNFTagQqNeECRIHssSacfQXPxVljaImvuSfrxf8i >> myQLzftiObINTIHSN4TVDKMyveYrU2hILCKfYuxnSJh29j35wsRSeftjntOEyHai >> RDnrLD3fCPk4h3hCY6l60nqu9MQfbgdSB/FItvhiBGYqXvGb4+wuBeU9RT9SwG8N >> XPih7nLNvqDNw38IkkDN >> =qcvG >> -----END PGP SIGNATURE----- >> -- >> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > -- > Cheers, > ~Blairo > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Best Regards, Wheat -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
