Messages in this thread | | | Date | Thu, 25 Jun 2009 11:26:43 +0200 | From | Jens Axboe <> | Subject | Re: [RFC][PATCH] mm: stop balance_dirty_pages doing too much work |
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On Thu, Jun 25 2009, Jens Axboe wrote: > On Thu, Jun 25 2009, Peter Zijlstra wrote: > > On Wed, 2009-06-24 at 15:27 -0700, Andrew Morton wrote: > > > On Wed, 24 Jun 2009 11:38:24 +0100 > > > Richard Kennedy <richard@rsk.demon.co.uk> wrote: > > > > > > > When writing to 2 (or more) devices at the same time, stop > > > > balance_dirty_pages moving dirty pages to writeback when it has reached > > > > the bdi threshold. This prevents balance_dirty_pages overshooting its > > > > limits and moving all dirty pages to writeback. > > > > > > > > > > > > Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk> > > > > --- > > > > Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > > After doing some integration and update work on the writeback branch, I > threw 2.6.31-rc1, 2.6.31-rc1+patch, 2.6.31-rc1+writeback into the test > mix. The writeback series include this patch as a prep patch. Results > for the mmap write test case: > > Kernel Throughput usr sys ctx util > -------------------------------------------------------------- > vanilla 184MB/sec 19.51% 50.49% 12995 82.88% > vanilla 184MB/sec 19.60% 50.77% 12846 83.47% > vanilla 182MB/sec 19.25% 51.18% 14692 82.76% > vanilla+patch 169MB/sec 18.08% 43.61% 9507 76.38% > vanilla+patch 170MB/sec 18.37% 43.46% 10275 76.62% > vanilla+patch 165MB/sec 17.59% 42.06% 10165 74.39% > writeback 215MB/sec 22.69% 53.23% 4085 92.32% > writeback 214MB/sec 24.31% 52.90% 4495 92.40% > writeback 208MB/sec 23.14% 52.12% 4067 91.68% > > To be perfectly clear: > > vanilla 2.6.31-rc1 stock > vanilla+patch 2.6.31-rc1 + bdi_thresh patch > writeback 2.6.31-rc1 + bdi_thresh patch + writeback series > > This is just a single spindle w/ext4, nothing fancy. I'll do a 3-series > run with the writeback and this patch backed out, to see if it makes a > difference here. I didn't do that initially, since the results were in > the range that I expected.
Results for writeback without the bdi_thresh patch
Kernel Throughput usr sys ctx util -------------------------------------------------------------- wb-bdi_thresh 211MB/sec 22.71% 53.30% 4050 91.19% wb-bdi_thresh 212MB/sec 22.78% 53.55% 4809 91.51% wb-bdi_thresh 212MB/sec 22.99% 54.23% 4715 93.10%
Not a lot of difference there, without more than three runs it's hard to say what is significant. Could be a small decrease in throughput, if the 208MB/sec results from above is an outlier (I think it is, ~215MB/sec is usually the most consistent result).
-- Jens Axboe
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