On Mon, 12 Jul 2010, Andrew Morton wrote: > On Sun, 11 Jul 2010 10:06:57 +0800 > Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote: > > > > > Signed-off-by: Richard Kennedy <richard@xxxxxxxxxxxxxxx> > > Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> > > --- > > mm/page-writeback.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > --- linux-next.orig/mm/page-writeback.c 2010-07-11 08:41:37.000000000 +0800 > > +++ linux-next/mm/page-writeback.c 2010-07-11 08:42:14.000000000 +0800 > > @@ -503,11 +503,12 @@ static void balance_dirty_pages(struct a > > }; > > > > get_dirty_limits(&background_thresh, &dirty_thresh, > > - &bdi_thresh, bdi); > > + &bdi_thresh, bdi); > > > > nr_reclaimable = global_page_state(NR_FILE_DIRTY) + > > - global_page_state(NR_UNSTABLE_NFS); > > - nr_writeback = global_page_state(NR_WRITEBACK); > > + global_page_state(NR_UNSTABLE_NFS); > > + nr_writeback = global_page_state(NR_WRITEBACK) + > > + global_page_state(NR_WRITEBACK_TEMP); > > > > bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); > > bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); > > > > hm, OK. Hm, hm. I'm not sure this is right. The VM has absolutely no control over NR_WRITEBACK_TEMP pages, they may clear quickly or may not make any progress. So it's usually wrong to make a decision based on NR_WRITEBACK_TEMP for an unrelated device. Using it in throttle_vm_writeout() would actually be deadlocky, since the userspace filesystem will probably depend on memory allocations to complete the writeout. The only place where we should be taking NR_WRITEBACK_TEMP into account is calculating the remaining memory that can be devided between dirtyers, and that's (clip_bdi_dirty_limit) where it is already used. > I wonder whether we could/should have unified NR_WRITEBACK_TEMP and > NR_UNSTABLE_NFS. Their "meanings" aren't quite the same, but perhaps > some "treat page as dirty because the fs is futzing with it" thing. AFAICS NR_UNSTABLE_NFS is something akin to NR_DIRTY, only on the server side. So nfs can very much do something about making NR_UNSTABLE_NFS go away, while there's nothing that can be done about NR_WRITEBACK_TEMP. Thanks, Miklos -- 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
