From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id E31736B0078 for ; Tue, 2 Mar 2010 17:22:53 -0500 (EST) Date: Tue, 2 Mar 2010 23:22:48 +0100 From: Andrea Righi Subject: Re: [PATCH -mmotm 3/3] memcg: dirty pages instrumentation Message-ID: <20100302222248.GD2369@linux> References: <1267478620-5276-1-git-send-email-arighi@develer.com> <1267478620-5276-4-git-send-email-arighi@develer.com> <20100301220208.GH3109@redhat.com> <20100301221830.GA5460@linux> <20100302150529.GA12855@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100302150529.GA12855@redhat.com> Sender: owner-linux-mm@kvack.org To: Vivek Goyal Cc: Balbir Singh , KAMEZAWA Hiroyuki , Suleiman Souhlal , Greg Thelen , Daisuke Nishimura , "Kirill A. Shutemov" , Andrew Morton , containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: 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 > > --- > > 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org