On Wed, Feb 03, 2010 at 10:24:54AM -0500, Vivek Goyal wrote: > On Wed, Feb 03, 2010 at 02:27:56PM +0800, Wu Fengguang wrote: > > Vivek, > > > > On Wed, Feb 03, 2010 at 06:38:03AM +0800, Vivek Goyal wrote: > > > On Tue, Feb 02, 2010 at 11:28:35PM +0800, Wu Fengguang wrote: > > > > Andrew, > > > > > > > > This is to lift default readahead size to 512KB, which I believe yields > > > > more I/O throughput without noticeably increasing I/O latency for today's HDD. > > > > > > > > > > Hi Fengguang, > > > > > > I was doing a quick test with the patches. I was using fio to run some > > > sequential reader threads. I have got one access to one Lun from an HP > > > EVA. In my case it looks like with the patches throughput has come down. > > > > Thank you for the quick testing! > > > > This patchset does 3 things: > > > > 1) 512K readahead size > > 2) new readahead algorithms > > 3) new readahead tracing/stats interfaces > > > > (1) will impact performance, while (2) _might_ impact performance in > > case of bugs. > > > > Would you kindly retest the patchset with readahead size manually set > > to 128KB? That would help identify the root cause of the performance > > drop: > > > > DEV=sda > > echo 128 > /sys/block/$DEV/queue/read_ahead_kb > > > > I have got two paths to the HP EVA and got multipath device setup(dm-3). I > noticed with vanilla kernel read_ahead_kb=128 after boot but with your patches > applied it is set to 4. So looks like something went wrong with device > size/capacity detection hence wrong defaults. Manually setting > read_ahead_kb=512, got me better performance as compare to vanilla kernel. > I put a printk in add_disk and noticed that for multipath device get_capacity() is returning 0 and that's why ra_pages is being set to 1. Thanks Vivek -- 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
