No change in behavior even in case of low memory systems. I confirmed it running on 1Gig machine. Thanks --Chakri On 9/28/07, Chakri n <chakriin5@xxxxxxxxx> wrote: > Here is a the snapshot of vmstats when the problem happened. I believe > this could help a little. > > crash> kmem -V > NR_FREE_PAGES: 680853 > NR_INACTIVE: 95380 > NR_ACTIVE: 26891 > NR_ANON_PAGES: 2507 > NR_FILE_MAPPED: 1832 > NR_FILE_PAGES: 119779 > NR_FILE_DIRTY: 0 > NR_WRITEBACK: 18272 > NR_SLAB_RECLAIMABLE: 1305 > NR_SLAB_UNRECLAIMABLE: 2085 > NR_PAGETABLE: 123 > NR_UNSTABLE_NFS: 0 > NR_BOUNCE: 0 > NR_VMSCAN_WRITE: 0 > > In my testing, I always saw the processes are waiting in > balance_dirty_pages_ratelimited(), never in throttle_vm_writeout() > path. > > But this could be because I have about 4Gig of memory in the system > and plenty of mem is still available around. > > I will rerun the test limiting memory to 1024MB and lets see if it > takes in any different path. > > Thanks > --Chakri > > > On 9/28/07, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, 28 Sep 2007 16:32:18 -0400 > > Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote: > > > > > On Fri, 2007-09-28 at 13:10 -0700, Andrew Morton wrote: > > > > On Fri, 28 Sep 2007 15:52:28 -0400 > > > > Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote: > > > > > > > > > On Fri, 2007-09-28 at 12:26 -0700, Andrew Morton wrote: > > > > > > On Fri, 28 Sep 2007 15:16:11 -0400 Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote: > > > > > > > Looking back, they were getting caught up in > > > > > > > balance_dirty_pages_ratelimited() and friends. See the attached > > > > > > > example... > > > > > > > > > > > > that one is nfs-on-loopback, which is a special case, isn't it? > > > > > > > > > > I'm not sure that the hang that is illustrated here is so special. It is > > > > > an example of a bog-standard ext3 write, that ends up calling the NFS > > > > > client, which is hanging. The fact that it happens to be hanging on the > > > > > nfsd process is more or less irrelevant here: the same thing could > > > > > happen to any other process in the case where we have an NFS server that > > > > > is down. > > > > > > > > hm, so ext3 got stuck in nfs via __alloc_pages direct reclaim? > > > > > > > > We should be able to fix that by marking the backing device as > > > > write-congested. That'll have small race windows, but it should be a 99.9% > > > > fix? > > > > > > No. The problem would rather appear to be that we're doing > > > per-backing_dev writeback (if I read sync_sb_inodes() correctly), but > > > we're measuring variables which are global to the VM. The backing device > > > that we are selecting may not be writing out any dirty pages, in which > > > case, we're just spinning in balance_dirty_pages_ratelimited(). > > > > OK, so it's unrelated to page reclaim. > > > > > Should we therefore perhaps be looking at adding per-backing_dev stats > > > too? > > > > That's what mm-per-device-dirty-threshold.patch and friends are doing. > > Whether it works adequately is not really known at this time. > > Unfortunately kernel developers don't test -mm much. > > > _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
