Hi Dave, On Mon, Nov 01, 2010 at 02:24:46PM +0800, Dave Chinner wrote: > On Wed, Oct 13, 2010 at 08:26:27PM +1100, Dave Chinner wrote: > > On Wed, Oct 13, 2010 at 04:26:12PM +0800, Wu Fengguang wrote: > > > On Wed, Oct 13, 2010 at 11:07:33AM +0800, Dave Chinner wrote: > > > > On Tue, Oct 12, 2010 at 10:17:16AM -0400, Christoph Hellwig wrote: > > > > > Wu, what's the state of this series? It looks like we'll need it > > > > > rather sooner than later - try to get at least the preparations in > > > > > ASAP would be really helpful. > > > > > > > > Not ready in it's current form. This load (creating millions of 1 > > > > byte files in parallel): > > > > > > > > $ /usr/bin/time ./fs_mark -D 10000 -S0 -n 100000 -s 1 -L 63 \ > > > > > -d /mnt/scratch/0 -d /mnt/scratch/1 \ > > > > > -d /mnt/scratch/2 -d /mnt/scratch/3 \ > > > > > -d /mnt/scratch/4 -d /mnt/scratch/5 \ > > > > > -d /mnt/scratch/6 -d /mnt/scratch/7 > > > > > > > > Locks up all the fs_mark processes spinning in traces like the > > > > following and no further progress is made when the inode cache > > > > fills memory. > > > > > > I reproduced the problem on a 6G/8p 2-socket 11-disk box. > > > > > > The root cause is, pageout() is somehow called with low scan priority, > > > which deserves more investigation. > > > > > > The direct cause is, balance_dirty_pages() then keeps nr_dirty too low, > > > which can be improved easily by not pushing down the soft dirty limit > > > to less than 1-second worth of dirty pages. > > > > > > My test box has two nodes, and their memory usage are rather unbalanced: > > > (Dave, maybe you have NUMA setup too?) > > > > No, I'm running the test in a single node VM. > > > > FYI, I'm running the test on XFS (16TB 12 disk RAID0 stripe), using > > the mount options "inode64,nobarrier,logbsize=262144,delaylog". > > Any update on the current status of this patchset? The last 3 patches to dynamically lower the 20% dirty limit seem to hurt writeback throughput when it goes too small. That's not surprising. I tried moderately increase the low bound of dynamic dirty limit but tests show that it's still not enough. Days ago I came up with another low bound scheme, however the test box has been running LKP (and other) benchmarks for the new -rc1 release.. Anyway I see some tricky points in deciding the low bound for dynamic dirty limit. It seems reasonable to bypass this feature for now, and to test/submit the other important parts first. I'm feeling relatively good about the first 14 patches to do IO-less balance_dirty_pages() and larger writeback chunk size. I'll repost them separately as v2 after returning to Shanghai. Some days ago I prepared some slides which has some figures on the old and new dirty throttling schemes. Hope it helps. http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/dirty-throttling.pdf Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>