Re: [PATCH 10/18] writeback: dirty position control - bdi reserve area
From: Wu Fengguang <hidden>
Date: 2011-09-18 14:17:05
Also in:
linux-fsdevel, lkml
On Mon, Sep 12, 2011 at 06:19:38PM +0800, Peter Zijlstra wrote:
On Wed, 2011-09-07 at 20:31 +0800, Wu Fengguang wrote:quoted
quoted
quoted
+ x_intercept = min(write_bw, freerun); + if (bdi_dirty < x_intercept) {So the point of the freerun point is that we never throttle before it, so basically all the below shouldn't be needed at all, right?Yes!quoted
quoted
+ if (bdi_dirty > x_intercept / 8) { + pos_ratio *= x_intercept; + do_div(pos_ratio, bdi_dirty); + } else + pos_ratio *= 8; + } + return pos_ratio; }Does that mean we can remove this whole block?
Right, if the bdi freerun concept is proved to work fine. Unfortunately I find it mostly yields lower performance than bdi reserve area. Patch is attached. If you would like me try other patches, I can easily kick off new tests and redo the comparison. Here is the nr_written numbers over various JBOD test cases, the larger, the better: bdi-reserve bdi-freerun diff case --------------------------------------------------------------------------------------- 38375271 31553807 -17.8% JBOD-10HDD-6G/xfs-100dd-1M-16p-5895M-20 30478879 28631491 -6.1% JBOD-10HDD-6G/xfs-10dd-1M-16p-5895M-20 29735407 28871956 -2.9% JBOD-10HDD-6G/xfs-1dd-1M-16p-5895M-20 30850350 28344165 -8.1% JBOD-10HDD-6G/xfs-2dd-1M-16p-5895M-20 17706200 16174684 -8.6% JBOD-10HDD-thresh=100M/xfs-100dd-1M-16p-5895M-100M 23374918 14376942 -38.5% JBOD-10HDD-thresh=100M/xfs-10dd-1M-16p-5895M-100M 20659278 19640375 -4.9% JBOD-10HDD-thresh=100M/xfs-1dd-1M-16p-5895M-100M 22517497 14552321 -35.4% JBOD-10HDD-thresh=100M/xfs-2dd-1M-16p-5895M-100M 68287850 61078553 -10.6% JBOD-10HDD-thresh=2G/xfs-100dd-1M-16p-5895M-2048M 33835247 32018425 -5.4% JBOD-10HDD-thresh=2G/xfs-10dd-1M-16p-5895M-2048M 30187817 29942083 -0.8% JBOD-10HDD-thresh=2G/xfs-1dd-1M-16p-5895M-2048M 30563144 30204022 -1.2% JBOD-10HDD-thresh=2G/xfs-2dd-1M-16p-5895M-2048M 34476862 34645398 +0.5% JBOD-10HDD-thresh=4G/xfs-10dd-1M-16p-5895M-4096M 30326479 30097263 -0.8% JBOD-10HDD-thresh=4G/xfs-1dd-1M-16p-5895M-4096M 30446767 30339683 -0.4% JBOD-10HDD-thresh=4G/xfs-2dd-1M-16p-5895M-4096M 40793956 45936678 +12.6% JBOD-10HDD-thresh=800M/xfs-100dd-1M-16p-5895M-800M 27481305 24867282 -9.5% JBOD-10HDD-thresh=800M/xfs-10dd-1M-16p-5895M-800M 25651257 22507406 -12.3% JBOD-10HDD-thresh=800M/xfs-1dd-1M-16p-5895M-800M 19849350 21298787 +7.3% JBOD-10HDD-thresh=800M/xfs-2dd-1M-16p-5895M-800M raw data by "grep": JBOD-10HDD-6G/xfs-100dd-1M-16p-5895M-20:10-3.1.0-rc4+/vmstat-end:nr_written 38375271 JBOD-10HDD-6G/xfs-10dd-1M-16p-5895M-20:10-3.1.0-rc4+/vmstat-end:nr_written 30478879 JBOD-10HDD-6G/xfs-1dd-1M-16p-5895M-20:10-3.1.0-rc4+/vmstat-end:nr_written 29735407 JBOD-10HDD-6G/xfs-2dd-1M-16p-5895M-20:10-3.1.0-rc4+/vmstat-end:nr_written 30850350 JBOD-10HDD-thresh=100M/xfs-100dd-1M-16p-5895M-100M:10-3.1.0-rc4+/vmstat-end:nr_written 17706200 JBOD-10HDD-thresh=100M/xfs-10dd-1M-16p-5895M-100M:10-3.1.0-rc4+/vmstat-end:nr_written 23374918 JBOD-10HDD-thresh=100M/xfs-1dd-1M-16p-5895M-100M:10-3.1.0-rc4+/vmstat-end:nr_written 20659278 JBOD-10HDD-thresh=100M/xfs-2dd-1M-16p-5895M-100M:10-3.1.0-rc4+/vmstat-end:nr_written 22517497 JBOD-10HDD-thresh=2G/xfs-100dd-1M-16p-5895M-2048M:10-3.1.0-rc4+/vmstat-end:nr_written 68287850 JBOD-10HDD-thresh=2G/xfs-10dd-1M-16p-5895M-2048M:10-3.1.0-rc4+/vmstat-end:nr_written 33835247 JBOD-10HDD-thresh=2G/xfs-1dd-1M-16p-5895M-2048M:10-3.1.0-rc4+/vmstat-end:nr_written 30187817 JBOD-10HDD-thresh=2G/xfs-2dd-1M-16p-5895M-2048M:10-3.1.0-rc4+/vmstat-end:nr_written 30563144 JBOD-10HDD-thresh=4G/xfs-10dd-1M-16p-5895M-4096M:10-3.1.0-rc4+/vmstat-end:nr_written 34476862 JBOD-10HDD-thresh=4G/xfs-1dd-1M-16p-5895M-4096M:10-3.1.0-rc4+/vmstat-end:nr_written 30326479 JBOD-10HDD-thresh=4G/xfs-2dd-1M-16p-5895M-4096M:10-3.1.0-rc4+/vmstat-end:nr_written 30446767 JBOD-10HDD-thresh=800M/xfs-100dd-1M-16p-5895M-800M:10-3.1.0-rc4+/vmstat-end:nr_written 40793956 JBOD-10HDD-thresh=800M/xfs-10dd-1M-16p-5895M-800M:10-3.1.0-rc4+/vmstat-end:nr_written 27481305 JBOD-10HDD-thresh=800M/xfs-1dd-1M-16p-5895M-800M:10-3.1.0-rc4+/vmstat-end:nr_written 25651257 JBOD-10HDD-thresh=800M/xfs-2dd-1M-16p-5895M-800M:10-3.1.0-rc4+/vmstat-end:nr_written 19849350 JBOD-10HDD-6G/xfs-100dd-1M-16p-5895M-20:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 31553807 JBOD-10HDD-6G/xfs-10dd-1M-16p-5895M-20:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 28631491 JBOD-10HDD-6G/xfs-1dd-1M-16p-5895M-20:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 28871956 JBOD-10HDD-6G/xfs-2dd-1M-16p-5895M-20:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 28344165 JBOD-10HDD-thresh=100M/xfs-100dd-1M-16p-5895M-100M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 16174684 JBOD-10HDD-thresh=100M/xfs-10dd-1M-16p-5895M-100M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 14376942 JBOD-10HDD-thresh=100M/xfs-1dd-1M-16p-5895M-100M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 19640375 JBOD-10HDD-thresh=100M/xfs-2dd-1M-16p-5895M-100M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 14552321 JBOD-10HDD-thresh=2G/xfs-100dd-1M-16p-5895M-2048M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 61078553 JBOD-10HDD-thresh=2G/xfs-10dd-1M-16p-5895M-2048M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 32018425 JBOD-10HDD-thresh=2G/xfs-1dd-1M-16p-5895M-2048M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 29942083 JBOD-10HDD-thresh=2G/xfs-2dd-1M-16p-5895M-2048M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 30204022 JBOD-10HDD-thresh=4G/xfs-10dd-1M-16p-5895M-4096M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 34645398 JBOD-10HDD-thresh=4G/xfs-1dd-1M-16p-5895M-4096M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 30097263 JBOD-10HDD-thresh=4G/xfs-2dd-1M-16p-5895M-4096M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 30339683 JBOD-10HDD-thresh=800M/xfs-100dd-1M-16p-5895M-800M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 45936678 JBOD-10HDD-thresh=800M/xfs-10dd-1M-16p-5895M-800M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 24867282 JBOD-10HDD-thresh=800M/xfs-1dd-1M-16p-5895M-800M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 22507406 JBOD-10HDD-thresh=800M/xfs-2dd-1M-16p-5895M-800M:10-3.1.0-rc4-bdi-freerun+/vmstat-end:nr_written 21298787
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