Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [RFC PATCH] v2 mm: balance_dirty_pages. reduce calls to global_page_state to reduce cache references | From | Richard Kennedy <> | Date | Mon, 07 Sep 2009 11:11:30 +0100 |
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On Sun, 2009-09-06 at 20:42 +0200, Jens Axboe wrote: > On Fri, Sep 04 2009, Richard Kennedy wrote: > > Reducing the number of times balance_dirty_pages calls global_page_state > > reduces the cache references and so improves write performance on a > > variety of workloads. > > > > 'perf stats' of simple fio write tests shows the reduction in cache > > access. > > Where the test is fio 'write,mmap,600Mb,pre_read' on AMD AthlonX2 with > > 3Gb memory (dirty_threshold approx 600 Mb) > > running each test 10 times, dropping the fasted & slowest values then > > taking > > the average & standard deviation > > > > average (s.d.) in millions (10^6) > > 2.6.31-rc8 648.6 (14.6) > > +patch 620.1 (16.5) > > This patch looks good to me, I have workloads too here where up to 10% > of the time is spent in balance_dirty_pages() because of this. I'll give > this patch a go on the box and test in question tomorrow, but it looks > promising. >
Thanks Jens,
It will be interesting to see how it works on different hardware & workload. How many cores are you going to run it on? wow 10% in balance_dirty_pages! Is that on a large server? or do you think its peculiar to your workload?
regards Richard
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