On Mon, Sep 07 2009, Richard Kennedy wrote: > 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? ~10% is rounded, it was 8.9x%. Pretty bad! It's a 64-way, and there's nothing special about the workload (just buffered IO with 4k blocks). It's just going rather fast. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
