On Tue, Mar 02, 2010 at 10:05:29AM -0500, Vivek Goyal wrote: > On Mon, Mar 01, 2010 at 11:18:31PM +0100, Andrea Righi wrote: > > On Mon, Mar 01, 2010 at 05:02:08PM -0500, Vivek Goyal wrote: > > > > @@ -686,10 +699,14 @@ void throttle_vm_writeout(gfp_t gfp_mask) > > > > */ > > > > dirty_thresh += dirty_thresh / 10; /* wheeee... */ > > > > > > > > - if (global_page_state(NR_UNSTABLE_NFS) + > > > > - global_page_state(NR_WRITEBACK) <= dirty_thresh) > > > > - break; > > > > - congestion_wait(BLK_RW_ASYNC, HZ/10); > > > > + > > > > + dirty = mem_cgroup_page_stat(MEMCG_NR_DIRTY_WRITEBACK_PAGES); > > > > + if (dirty < 0) > > > > + dirty = global_page_state(NR_UNSTABLE_NFS) + > > > > + global_page_state(NR_WRITEBACK); > > > > > > dirty is unsigned long. As mentioned last time, above will never be true? > > > In general these patches look ok to me. I will do some testing with these. > > > > Re-introduced the same bug. My bad. :( > > > > The value returned from mem_cgroup_page_stat() can be negative, i.e. > > when memory cgroup is disabled. We could simply use a long for dirty, > > the unit is in # of pages so s64 should be enough. Or cast dirty to long > > only for the check (see below). > > > > Thanks! > > -Andrea > > > > Signed-off-by: Andrea Righi <arighi@xxxxxxxxxxx> > > --- > > mm/page-writeback.c | 2 +- > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > > index d83f41c..dbee976 100644 > > --- a/mm/page-writeback.c > > +++ b/mm/page-writeback.c > > @@ -701,7 +701,7 @@ void throttle_vm_writeout(gfp_t gfp_mask) > > > > > > dirty = mem_cgroup_page_stat(MEMCG_NR_DIRTY_WRITEBACK_PAGES); > > - if (dirty < 0) > > + if ((long)dirty < 0) > > This will also be problematic as on 32bit systems, your uppper limit of > dirty memory will be 2G? > > I guess, I will prefer one of the two. > > - return the error code from function and pass a pointer to store stats > in as function argument. > > - Or Peter's suggestion of checking mem_cgroup_has_dirty_limit() and if > per cgroup dirty control is enabled, then use per cgroup stats. In that > case you don't have to return negative values. > > Only tricky part will be careful accouting so that none of the stats go > negative in corner cases of migration etc. What do you think about Peter's suggestion + the locking stuff? (see the previous email). Otherwise, I'll choose the other solution, passing a pointer and always return the error code is not bad. Thanks, -Andrea -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>