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Date: Thu, 20 Jun 2013 17:42:04 +0800 From: Bob Liu <lliubbo@...il.com> To: Seth Jennings <sjenning@...ux.vnet.ibm.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Nitin Gupta <ngupta@...are.org>, Minchan Kim <minchan@...nel.org>, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, Dan Magenheimer <dan.magenheimer@...cle.com>, Robert Jennings <rcj@...ux.vnet.ibm.com>, Jenifer Hopper <jhopper@...ibm.com>, Mel Gorman <mgorman@...e.de>, Johannes Weiner <jweiner@...hat.com>, Rik van Riel <riel@...hat.com>, Larry Woodman <lwoodman@...hat.com>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Dave Hansen <dave@...1.net>, Joe Perches <joe@...ches.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, Cody P Schafer <cody@...ux.vnet.ibm.com>, Hugh Dickens <hughd@...gle.com>, Paul Mackerras <paulus@...ba.org>, Linux-MM <linux-mm@...ck.org>, Linux-Kernel <linux-kernel@...r.kernel.org>, devel@...verdev.osuosl.org Subject: Re: [PATCHv13 3/4] zswap: add to mm/ On Thu, Jun 20, 2013 at 10:37 AM, Seth Jennings <sjenning@...ux.vnet.ibm.com> wrote: > On Mon, Jun 17, 2013 at 02:20:05PM +0800, Bob Liu wrote: >> Hi Seth, >> >> On Tue, Jun 4, 2013 at 4:33 AM, Seth Jennings >> <sjenning@...ux.vnet.ibm.com> wrote: >> > zswap is a thin backend for frontswap that takes pages that are in the process >> > of being swapped out and attempts to compress them and store them in a >> > RAM-based memory pool. This can result in a significant I/O reduction on the >> > swap device and, in the case where decompressing from RAM is faster than >> > reading from the swap device, can also improve workload performance. >> > >> > It also has support for evicting swap pages that are currently compressed in >> > zswap to the swap device on an LRU(ish) basis. This functionality makes zswap a >> > true cache in that, once the cache is full, the oldest pages can be moved out >> > of zswap to the swap device so newer pages can be compressed and stored in >> > zswap. >> > >> > This patch adds the zswap driver to mm/ >> > >> >> Do you have any more benchmark can share with me ? To figure out that >> we can benefit from zswap. >> >> I found zswap will cause performance drop when using mmtests-0.10 to test it. >> The config file I'm using is: config-global-dhp__parallelio-memcachetest >> >> The result is: >> (v3.10-rc4-2G-nozswap was without zswap but the performance is better.) >> >> v3.10-rc4 v3.10-rc4 >> 2G-zswap-base 2G-nozswap >> Ops memcachetest-0M 604.00 ( 0.00%) 1077.00 ( 78.31%) >> Ops memcachetest-198M 630.00 ( 0.00%) 1007.00 ( 59.84%) >> Ops memcachetest-430M 609.00 ( 0.00%) 939.00 ( 54.19%) >> Ops memcachetest-661M 604.00 ( 0.00%) 845.00 ( 39.90%) >> Ops memcachetest-893M 591.00 ( 0.00%) 839.00 ( 41.96%) >> Ops memcachetest-1125M 599.00 ( 0.00%) 781.00 ( 30.38%) >> Ops memcachetest-1356M 588.00 ( 0.00%) 771.00 ( 31.12%) >> Ops io-duration-0M 0.00 ( 0.00%) 1.00 (-99.00%) >> Ops io-duration-198M 177.00 ( 0.00%) 21.00 ( 88.14%) >> Ops io-duration-430M 168.00 ( 0.00%) 25.00 ( 85.12%) >> Ops io-duration-661M 214.00 ( 0.00%) 30.00 ( 85.98%) >> Ops io-duration-893M 186.00 ( 0.00%) 32.00 ( 82.80%) >> Ops io-duration-1125M 175.00 ( 0.00%) 42.00 ( 76.00%) >> Ops io-duration-1356M 245.00 ( 0.00%) 51.00 ( 79.18%) >> Ops swaptotal-0M 487760.00 ( 0.00%) 459754.00 ( 5.74%) >> Ops swaptotal-198M 563581.00 ( 0.00%) 485194.00 ( 13.91%) >> Ops swaptotal-430M 579472.00 ( 0.00%) 500817.00 ( 13.57%) >> Ops swaptotal-661M 568086.00 ( 0.00%) 524209.00 ( 7.72%) >> Ops swaptotal-893M 584405.00 ( 0.00%) 509846.00 ( 12.76%) >> Ops swaptotal-1125M 572992.00 ( 0.00%) 534115.00 ( 6.78%) >> Ops swaptotal-1356M 573259.00 ( 0.00%) 529814.00 ( 7.58%) >> Ops swapin-0M 231250.00 ( 0.00%) 236069.00 ( -2.08%) >> Ops swapin-198M 312259.00 ( 0.00%) 239149.00 ( 23.41%) >> Ops swapin-430M 327178.00 ( 0.00%) 246803.00 ( 24.57%) >> Ops swapin-661M 319575.00 ( 0.00%) 273644.00 ( 14.37%) >> Ops swapin-893M 328195.00 ( 0.00%) 257327.00 ( 21.59%) >> Ops swapin-1125M 317345.00 ( 0.00%) 271109.00 ( 14.57%) >> Ops swapin-1356M 312858.00 ( 0.00%) 266050.00 ( 14.96%) >> Ops minorfaults-0M 592150.00 ( 0.00%) 646076.00 ( -9.11%) >> Ops minorfaults-198M 637339.00 ( 0.00%) 676441.00 ( -6.14%) >> Ops minorfaults-430M 626228.00 ( 0.00%) 684715.00 ( -9.34%) >> Ops minorfaults-661M 625089.00 ( 0.00%) 670639.00 ( -7.29%) >> Ops minorfaults-893M 612877.00 ( 0.00%) 669723.00 ( -9.28%) >> Ops minorfaults-1125M 624800.00 ( 0.00%) 667025.00 ( -6.76%) >> Ops minorfaults-1356M 618800.00 ( 0.00%) 657600.00 ( -6.27%) >> Ops majorfaults-0M 67664.00 ( 0.00%) 40060.00 ( 40.80%) >> Ops majorfaults-198M 72377.00 ( 0.00%) 39517.00 ( 45.40%) >> Ops majorfaults-430M 71822.00 ( 0.00%) 38895.00 ( 45.85%) >> Ops majorfaults-661M 70009.00 ( 0.00%) 39625.00 ( 43.40%) >> Ops majorfaults-893M 74988.00 ( 0.00%) 38073.00 ( 49.23%) >> Ops majorfaults-1125M 72458.00 ( 0.00%) 38206.00 ( 47.27%) >> Ops majorfaults-1356M 70549.00 ( 0.00%) 37430.00 ( 46.94%) > > Just made a mmtests run of my own and got very different results: > It's strange, I'll update to rc6 and try again. By the way, are you using 824 hardware compressor instead of lzo? > parallelio-memcachetest > v3.10-rc6 v3.10-rc6 > base zswap > Ops memcachetest-0M 7815.00 ( 0.00%) 7843.00 ( 0.36%) > Ops memcachetest-596M 12116.00 ( 0.00%) 12158.00 ( 0.35%) > Ops memcachetest-1989M 2226.00 ( 0.00%) 5314.00 (138.72%) > Ops memcachetest-3382M 1910.00 ( 0.00%) 4427.00 (131.78%) > Ops io-duration-0M 0.00 ( 0.00%) 0.00 ( 0.00%) > Ops io-duration-596M 18.00 ( 0.00%) 12.00 ( 33.33%) > Ops io-duration-1989M 82.00 ( 0.00%) 57.00 ( 30.49%) > Ops io-duration-3382M 91.00 ( 0.00%) 94.00 ( -3.30%) > Ops swaptotal-0M 0.00 ( 0.00%) 0.00 ( 0.00%) > Ops swaptotal-596M 0.00 ( 0.00%) 0.00 ( 0.00%) > Ops swaptotal-1989M 305182.00 ( 0.00%) 91508.00 ( 70.02%) > Ops swaptotal-3382M 353389.00 ( 0.00%) 74932.00 ( 78.80%) > Ops swapin-0M 0.00 ( 0.00%) 0.00 ( 0.00%) > Ops swapin-596M 0.00 ( 0.00%) 0.00 ( 0.00%) > Ops swapin-1989M 131071.00 ( 0.00%) 45657.00 ( 65.17%) > Ops swapin-3382M 135003.00 ( 0.00%) 37245.00 ( 72.41%) > Ops minorfaults-0M 1201113.00 ( 0.00%) 1201229.00 ( -0.01%) > Ops minorfaults-596M 1218437.00 ( 0.00%) 1218824.00 ( -0.03%) > Ops minorfaults-1989M 1260652.00 ( 0.00%) 1270762.00 ( -0.80%) > Ops minorfaults-3382M 1251389.00 ( 0.00%) 1248756.00 ( 0.21%) > Ops majorfaults-0M 0.00 ( 0.00%) 0.00 ( 0.00%) > Ops majorfaults-596M 34.00 ( 0.00%) 0.00 ( 0.00%) > Ops majorfaults-1989M 16561.00 ( 0.00%) 7789.00 ( 52.97%) > Ops majorfaults-3382M 17031.00 ( 0.00%) 6372.00 ( 62.59%) > > Basically the results show that once swapping starts (which happens even in the > 0MB case in your results which is puzzling), zswap reduces swapins by around > 70% (and as a result swaptotal and majorfaults) and increases memcached > throughput by over 130% compared to the normal swapping case w/o zswap. > > This test illustrates a great use case for zswap. The test is really designed > to detect suboptimal page reclaim decisions. Ideally the memcached pages would > never reach the end of the inactive LRU and be swapped out. However, since > there is a lot of I/O going on, if a memcached page does get put on the > inactive list, it can quickly move to the end. In this case, zswap catches the > page and memcached has a chance to fault it back in from the compressed cache > before actual swapping to disk occurs. > > Seth > -- Regards, --Bob -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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