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Date: Mon, 02 Nov 2009 21:26:49 +0100 From: Thomas Pilarski <thomas.pi@...or.de> To: Mike Galbraith <efault@....de> Cc: Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Andrew Morton <akpm@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [Bug 12309] Large I/O operations result in slow performance and high iowait times Hi Mike, Am Montag, den 02.11.2009, 16:56 +0100 schrieb Mike Galbraith: > > --- Comment #412 from Thomas Pilarski <thomas.pi@...or.de> 2009-11-01 21:28:24 --- > > Created an attachment (id=23618) > > --> (http://bugzilla.kernel.org/attachment.cgi?id=23618) > > Simple sleeper test case > > > > [...] > > Can you please try the latest -rc? I spent the day trying to coax a > latency spike out of -tip, including thumping disk with dd, mysql+oltp > rw test et al, and failed. I have just tries the rc5 and the spikes are still there, but much shorter. The test case does not show latencies <15ms. For these tests, I have reduced the minimum printout time to 3ms. The notebook with the first generation ssd in not available for testing, till next weekend. The freezes still exists with the kernel 32, but the freezes are more seldom and shorter. But I am not sure, as the X-Server is unusable on my machine in vesa mode with the rc5 kernel. Here are the results with the rc5 kernel and the fedora kernel vmlinuz-2.6.31.5-96.fc12.x86_64. I have changed my system yesterday. This test was made during a kernel build. Kernel 32: Timediff 220114: 3.01ms Total: 9.44ms Timediff 222460: 3.58ms Total: 10.82ms Timediff 234968: 3.23ms Total: 9.99ms Timediff 235916: 3.19ms Total: 11.50ms Timediff 236448: 3.55ms Total: 12.71ms Timediff 236485: 3.56ms Total: 16.14ms Timediff 236793: 3.49ms Total: 10.54ms Timediff 237076: 3.58ms Total: 11.29ms Timediff 237417: 3.88ms Total: 12.05ms Timediff 237694: 4.03ms Total: 15.36ms Timediff 238039: 3.55ms Total: 11.64ms Timediff 238347: 3.57ms Total: 10.23ms Timediff 278945: 4.82ms Total: 11.25ms Timediff 306303: 3.14ms Total: 10.22ms Timediff 310378: 3.00ms Total: 9.49ms Timediff 312685: 3.08ms Total: 9.53ms Timediff 323824: 3.93ms Total: 10.37ms Timediff 324150: 3.25ms Total: 9.90ms With the kernel 31 the latencies are ~3-5ms with about 10 spikes every 10 seconds >15ms. This test was made with eight concurrent writing operations. With kernel 32, the system freezes for up to 5 seconds. With the 31 kernel the system is unusable and freezes for more than 15 seconds. Kernel 32: Timediff 541833: 5.45ms Total: 13.96ms Timediff 541835: 5.96ms Total: 20.69ms Timediff 562105: 47.17ms Total: 54.12ms Timediff 562108: 4.72ms Total: 62.26ms Timediff 562873: 3.51ms Total: 9.87ms Timediff 562965: 4.80ms Total: 14.66ms Timediff 563258: 5.82ms Total: 12.06ms Timediff 564122: 4.54ms Total: 10.64ms Timediff 564320: 4.41ms Total: 15.62ms Timediff 565994: 3.52ms Total: 11.82ms Timediff 571837: 4.84ms Total: 13.08ms Timediff 574202: 6.26ms Total: 15.30ms Timediff 580009: 4.26ms Total: 12.17ms Timediff 581148: 5.97ms Total: 14.01ms Timediff 604232: 8.06ms Total: 18.51ms Timediff 607985: 36.17ms Total: 43.24ms Timediff 607988: 6.44ms Total: 51.55ms Timediff 607991: 3.96ms Total: 57.71ms Timediff 608839: 3.15ms Total: 11.97ms Timediff 621034: 11.70ms Total: 18.12ms Timediff 626739: 14.79ms Total: 21.28ms Timediff 628626: 4.29ms Total: 10.76ms Timediff 630171: 3.17ms Total: 11.80ms Timediff 630230: 4.68ms Total: 16.98ms Timediff 645119: 5.24ms Total: 14.22ms Timediff 645126: 3.01ms Total: 18.15ms Timediff 665520: 23.39ms Total: 30.43ms Timediff 665522: 7.21ms Total: 38.46ms Timediff 665524: 4.05ms Total: 45.33ms Timediff 665525: 12.37ms Total: 57.62ms Timediff 665526: 8.55ms Total: 66.10ms Timediff 666559: 7.40ms Total: 13.55ms Timediff 666722: 9.98ms Total: 17.39ms Timediff 692704: 3.91ms Total: 14.77ms Timediff 709733: 5.22ms Total: 12.83ms Timediff 713358: 9.96ms Total: 16.92ms Timediff 713711: 6.71ms Total: 13.14ms Timediff 713762: 9.60ms Total: 22.32ms Timediff 715036: 6.61ms Total: 13.02ms Timediff 715333: 8.16ms Total: 14.72ms Timediff 716295: 5.69ms Total: 11.85ms Timediff 717586: 13.30ms Total: 19.65ms Timediff 720534: 4.00ms Total: 11.11ms Timediff 724444: 3.78ms Total: 11.39ms Timediff 742710: 5.91ms Total: 16.60ms Timediff 746094: 9.36ms Total: 16.82ms Timediff 746253: 3.01ms Total: 10.58ms Timediff 750732: 3.12ms Total: 9.07ms Timediff 750970: 4.66ms Total: 10.74ms Timediff 751004: 11.48ms Total: 22.13ms Timediff 751344: 3.24ms Total: 10.00ms Timediff 752615: 6.09ms Total: 12.77ms Timediff 752692: 10.48ms Total: 23.34ms Timediff 752750: 5.66ms Total: 24.95ms Timediff 753517: 5.40ms Total: 11.87ms Timediff 764817: 3.01ms Total: 10.55ms Timediff 780410: 7.68ms Total: 14.25ms Timediff 781238: 3.22ms Total: 9.80ms Timediff 781751: 4.32ms Total: 10.41ms Timediff 783193: 3.02ms Total: 9.11ms Timediff 783376: 5.04ms Total: 13.13ms Timediff 783443: 10.43ms Total: 21.73ms Timediff 783849: 3.56ms Total: 9.63ms Timediff 783998: 4.75ms Total: 11.03ms Timediff 789922: 14.12ms Total: 23.77ms Timediff 791834: 10.17ms Total: 17.70ms Timediff 791968: 4.33ms Total: 10.70ms Timediff 803919: 8.23ms Total: 18.95ms Timediff 814559: 22.20ms Total: 29.33ms Timediff 814561: 8.97ms Total: 39.13ms Timediff 814562: 9.33ms Total: 48.39ms Timediff 814564: 3.54ms Total: 52.41ms Timediff 814565: 11.44ms Total: 63.78ms Timediff 814959: 6.00ms Total: 12.12ms Timediff 816641: 7.36ms Total: 14.17ms Timediff 817586: 8.70ms Total: 17.21ms Timediff 817600: 3.01ms Total: 23.88ms Timediff 818541: 11.60ms Total: 17.78ms Timediff 836524: 9.60ms Total: 18.08ms Timediff 847263: 7.33ms Total: 14.82ms Timediff 847581: 3.92ms Total: 10.61ms Timediff 857510: 5.21ms Total: 16.21ms Timediff 875426: 34.63ms Total: 42.72ms Timediff 875428: 15.56ms Total: 58.63ms Timediff 875430: 4.25ms Total: 64.14ms Timediff 875432: 9.90ms Total: 74.97ms Kernel 31: Timediff 3051355: 3.56ms Total: 12.01ms Timediff 3052075: 3.04ms Total: 11.18ms Timediff 3052727: 5.05ms Total: 11.98ms Timediff 3052728: 6.32ms Total: 18.23ms Timediff 3064913: 209.00ms Total: 215.89ms Timediff 3087930: 7.33ms Total: 13.96ms Timediff 3087931: 8.93ms Total: 22.84ms Timediff 3088666: 10.73ms Total: 17.63ms Timediff 3129442: 50.38ms Total: 57.85ms Timediff 3129443: 6.97ms Total: 64.75ms Timediff 3129444: 3.97ms Total: 68.64ms Timediff 3129561: 9.71ms Total: 15.97ms Timediff 3147899: 195.24ms Total: 202.19ms Timediff 3202247: 4.25ms Total: 12.78ms Timediff 3202480: 12.92ms Total: 19.53ms Timediff 3202811: 8.06ms Total: 14.62ms Timediff 3202812: 9.92ms Total: 24.48ms Timediff 3207028: 10.27ms Total: 19.03ms Timediff 3221487: 155.74ms Total: 162.68ms Timediff 3245089: 16.85ms Total: 23.19ms Timediff 3245090: 5.94ms Total: 29.07ms Timediff 3245091: 8.93ms Total: 37.95ms Timediff 3245092: 8.97ms Total: 46.85ms Timediff 3283440: 33.92ms Total: 41.07ms And this test during coping a file from one encrypted ext4 to a ext3 (data=ordered) partition. Kernel 32: Timediff 3519663: 4.30ms Total: 12.02ms Timediff 3519949: 5.09ms Total: 15.30ms Timediff 3520668: 4.49ms Total: 13.65ms Timediff 3524199: 3.56ms Total: 12.34ms Timediff 3525677: 4.10ms Total: 10.87ms Timediff 3526071: 13.81ms Total: 21.45ms Timediff 3526347: 11.53ms Total: 18.21ms Timediff 3526606: 10.62ms Total: 17.31ms Timediff 3526847: 9.90ms Total: 16.45ms Timediff 3527074: 9.07ms Total: 15.46ms Timediff 3529137: 5.50ms Total: 14.79ms Timediff 3563927: 3.39ms Total: 13.19ms Timediff 3622363: 3.96ms Total: 11.33ms Timediff 3626268: 6.53ms Total: 14.77ms Timediff 3626270: 5.92ms Total: 21.57ms Timediff 3644582: 11.01ms Total: 21.53ms Timediff 3654125: 8.69ms Total: 16.16ms Timediff 3663323: 6.19ms Total: 12.83ms Timediff 3663471: 5.55ms Total: 12.51ms Timediff 3669593: 4.50ms Total: 11.63ms Timediff 3679411: 4.84ms Total: 12.92ms Timediff 3710494: 8.88ms Total: 18.84ms Kernel 31: Timediff 418897: 7.69ms Total: 32.66ms Timediff 419046: 12.44ms Total: 21.66ms Timediff 419048: 4.89ms Total: 26.98ms Timediff 419788: 3.12ms Total: 13.01ms Timediff 424485: 3.96ms Total: 12.58ms Timediff 424492: 8.26ms Total: 20.69ms Timediff 424909: 12.77ms Total: 22.17ms Timediff 425081: 4.48ms Total: 23.68ms Timediff 425362: 10.47ms Total: 19.98ms Timediff 425365: 8.95ms Total: 28.83ms Timediff 438326: 11.14ms Total: 21.51ms Timediff 438534: 4.49ms Total: 24.64ms Timediff 438817: 4.50ms Total: 26.54ms Timediff 439276: 3.35ms Total: 10.78ms Timediff 439278: 12.95ms Total: 23.66ms Timediff 439717: 17.05ms Total: 26.49ms Timediff 439937: 15.20ms Total: 22.50ms Timediff 451047: 4.21ms Total: 12.41ms Timediff 451454: 10.25ms Total: 19.86ms Timediff 451606: 3.56ms Total: 23.22ms Timediff 451984: 5.60ms Total: 18.60ms The last test: dd if=/dev/zero of=test1 bs=1M count=8K to a ext3 (data=ordered) partition Kernel 32: (Throughput 34,3 MB/s) Timediff 3758684: 3.95ms Total: 14.74ms Timediff 3761994: 3.53ms Total: 13.84ms Timediff 3765917: 3.32ms Total: 14.68ms Timediff 3770973: 3.63ms Total: 14.05ms Timediff 3771301: 3.27ms Total: 13.44ms Timediff 3774010: 3.02ms Total: 13.68ms Timediff 3774263: 3.96ms Total: 14.41ms Timediff 3777798: 4.01ms Total: 15.53ms Timediff 3787290: 3.55ms Total: 14.39ms Timediff 3787611: 3.60ms Total: 14.21ms Timediff 3790433: 3.37ms Total: 14.14ms Timediff 3790676: 3.09ms Total: 13.66ms Timediff 3792464: 3.25ms Total: 13.16ms Timediff 3792747: 3.34ms Total: 14.28ms Timediff 3795961: 3.60ms Total: 13.72ms Timediff 3797212: 4.00ms Total: 14.60ms Timediff 3798908: 3.76ms Total: 14.49ms Timediff 3803617: 4.48ms Total: 14.85ms Timediff 3803855: 4.06ms Total: 14.67ms Timediff 3805129: 3.71ms Total: 14.51ms Timediff 3805431: 4.52ms Total: 15.55ms Timediff 3807400: 4.17ms Total: 15.40ms Timediff 3809013: 5.45ms Total: 16.39ms Timediff 3811439: 3.51ms Total: 12.84ms Timediff 3811680: 3.75ms Total: 14.83ms Timediff 3823024: 4.02ms Total: 14.95ms Timediff 3828474: 4.25ms Total: 14.74ms Timediff 3836624: 3.03ms Total: 13.54ms Timediff 3836919: 4.86ms Total: 16.72ms Timediff 3845647: 3.74ms Total: 14.55ms Timediff 3847453: 4.41ms Total: 15.06ms Timediff 3847758: 3.12ms Total: 12.52ms Timediff 3860736: 3.26ms Total: 14.12ms Timediff 3860824: 5.95ms Total: 19.24ms Timediff 3864060: 4.24ms Total: 14.29ms Timediff 3866621: 4.02ms Total: 14.38ms Timediff 3866863: 3.25ms Total: 13.00ms Timediff 3871055: 4.54ms Total: 15.55ms Timediff 3876891: 3.66ms Total: 15.05ms Timediff 3883110: 4.13ms Total: 14.36ms Timediff 3883432: 4.69ms Total: 15.04ms Timediff 3890870: 4.31ms Total: 15.56ms Timediff 3899279: 4.50ms Total: 15.60ms Timediff 3906261: 3.82ms Total: 12.61ms Timediff 3906605: 4.85ms Total: 15.35ms Timediff 3908836: 4.27ms Total: 15.62ms Timediff 3909079: 4.50ms Total: 15.37ms Timediff 3910731: 3.57ms Total: 12.76ms Timediff 3911044: 4.70ms Total: 14.80ms Timediff 3912716: 4.67ms Total: 15.22ms Timediff 3913027: 4.59ms Total: 15.39ms Timediff 3914187: 4.00ms Total: 13.14ms Timediff 3919700: 3.11ms Total: 14.77ms Timediff 3921904: 4.76ms Total: 15.35ms Timediff 3926853: 3.32ms Total: 14.19ms Timediff 3926920: 4.03ms Total: 17.92ms Timediff 3929504: 3.73ms Total: 14.70ms Timediff 3929767: 4.13ms Total: 13.80ms Timediff 3931576: 3.62ms Total: 14.70ms Timediff 3931670: 3.04ms Total: 16.53ms Timediff 3933039: 5.11ms Total: 16.19ms Timediff 3935405: 3.83ms Total: 15.33ms Timediff 3939429: 3.23ms Total: 14.50ms Timediff 3940606: 4.34ms Total: 15.47ms Timediff 3940825: 3.20ms Total: 15.06ms Timediff 3950448: 3.14ms Total: 14.98ms Timediff 3950727: 3.16ms Total: 14.17ms Timediff 3968492: 3.16ms Total: 14.46ms Kernel 31: (Throughput 33,7 MB/s) Timediff 3759425: 8.49ms Total: 16.14ms Timediff 3766033: 7.79ms Total: 15.44ms Timediff 3786336: 10.13ms Total: 17.75ms Timediff 3788547: 4.97ms Total: 12.63ms Timediff 3790714: 4.80ms Total: 12.82ms Timediff 3792863: 4.82ms Total: 12.52ms Timediff 3795029: 5.45ms Total: 13.28ms Timediff 3797198: 4.78ms Total: 13.02ms Timediff 3797664: 109.83ms Total: 118.02ms Timediff 3800212: 4.91ms Total: 13.50ms Timediff 3806437: 5.78ms Total: 15.46ms Timediff 3807558: 14.73ms Total: 23.01ms Timediff 3808257: 16.44ms Total: 24.05ms Timediff 3810303: 14.62ms Total: 23.92ms Timediff 3812049: 18.96ms Total: 27.83ms Timediff 3813914: 11.95ms Total: 20.75ms Timediff 3814444: 4.79ms Total: 12.90ms Timediff 3818132: 5.22ms Total: 14.41ms Timediff 3831185: 5.02ms Total: 14.17ms Timediff 3833362: 5.75ms Total: 13.66ms Timediff 3845301: 8.16ms Total: 18.06ms As you can see, the spikes are still there, but much more seldom and shorter. Perhaps the opposite way, a delay or something equal in the block-layer or scheduler to maximize this problem, can help to locate the culprit. Thomas -- 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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