From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta12.messagelabs.com (mail6.bemta12.messagelabs.com [216.82.250.247]) by kanga.kvack.org (Postfix) with ESMTP id 69C446B0012 for ; Wed, 18 May 2011 20:37:53 -0400 (EDT) Received: by qyk30 with SMTP id 30so1582507qyk.14 for ; Wed, 18 May 2011 17:37:51 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: Date: Thu, 19 May 2011 09:37:51 +0900 Message-ID: Subject: Re: [PATCH mmotm] add the pagefault count into memcg stats: shmem fix From: Minchan Kim Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins Cc: Andrew Morton , Ying Han , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Daisuke Nishimura , Balbir Singh , linux-mm@kvack.org On Thu, May 19, 2011 at 9:28 AM, Hugh Dickins wrote: > On Thu, 19 May 2011, Minchan Kim wrote: >> On Wed, May 18, 2011 at 3:24 AM, Hugh Dickins wrote: >> > mem_cgroup_count_vm_event() should update the PGMAJFAULT count for the >> > target mm, not for current mm (but of course they're usually the same)= . >> > >> > We don't know the target mm in shmem_getpage(), so do it at the outer >> > level in shmem_fault(); and it's easier to follow if we move the >> > count_vm_event(PGMAJFAULT) there too. >> > >> > Hah, it was using __count_vm_event() before, sneaking that update into >> > the unpreemptible section under info->lock: well, it comes to the same >> > on x86 at least, and I still think it's best to keep these together. >> > >> > Signed-off-by: Hugh Dickins >> >> It's good to me but I have a nitpick. >> >> You are changing behavior a bit. >> Old behavior is to account FAULT although the operation got failed. >> But new one is to not account it. >> I think we have to account it regardless of whether it is successful or = not. >> That's because it is fact fault happens. > > That's a good catch: something I didn't think of at all. > > However, it looks as if the patch remains correct, and is fixing > a bug (or inconsistency) that we hadn't noticed before. > > If you look through filemap_fault() or do_swap_page() (or even > ncp_file_mmap_fault(), though I don't take that one as canonical!), > they clearly do not count the major fault on error (except in the > case where VM_FAULT_MAJOR needs VM_FAULT_RETRY, then gets > VM_FAULT_ERROR on the retry). > > So, shmem.c was the odd one out before. =C2=A0If you feel very strongly > about it ("it is fact fault happens") you could submit a patch to > change them all - but I think just leave them as is. Okay. I don't feel it strongly now. Then, could you repost your patch with corrected description about this behavior change which is a bug or inconsistency whatever. :) > > Hugh > --=20 Kind regards, Minchan Kim -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org