From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx186.postini.com [74.125.245.186]) by kanga.kvack.org (Postfix) with SMTP id 0AA296B13F0 for ; Thu, 2 Feb 2012 05:54:25 -0500 (EST) Received: by iagz16 with SMTP id z16so4200861iag.14 for ; Thu, 02 Feb 2012 02:54:25 -0800 (PST) Message-ID: <4F2A6B5F.3090303@gmail.com> Date: Thu, 02 Feb 2012 18:54:23 +0800 From: Sha Zhengju MIME-Version: 1.0 Subject: Re: [PATCH] memcg: make threshold index in the right position References: <1328175919-11209-1-git-send-email-handai.szj@taobao.com> <20120202101410.GA12291@shutemov.name> In-Reply-To: <20120202101410.GA12291@shutemov.name> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: linux-mm@kvack.org, cgroups@vger.kernel.org, KAMEZAWA Hiroyuki On 02/02/2012 06:14 PM, Kirill A. Shutemov wrote: > On Thu, Feb 02, 2012 at 05:45:19PM +0800, Sha Zhengju wrote: >> From: Sha Zhengju >> >> Index current_threshold may point to threshold that just equal to >> usage after __mem_cgroup_threshold is triggerd. > I don't see it. Could you describe conditions? > It is because of the following code path in __mem_cgroup_threshold: { ... i = t->current_threshold; for (; i >= 0 && unlikely(t->entries[i].threshold > usage); i--) eventfd_signal(t->entries[i].eventfd, 1); i++; for (; i < t->size && unlikely(t->entries[i].threshold <= usage); i++) eventfd_signal(t->entries[i].eventfd, 1); t->current_threshold = i - 1; ... } For example: now: threshold array: 3 5 7 9 (usage = 6) ^ index next turn: threshold array: 3 5 7 9 (usage = 7) ^ index after registering a new event(threshold = 10): threshold array: 3 5 7 9 10 (usage = 7) ^ index >> But after registering >> a new event, it will change (pointing to threshold just below usage). >> So make it consistent here. >> >> Cc: KAMEZAWA Hiroyuki >> Cc: Kirill A. Shutemov >> Signed-off-by: Sha Zhengju >> --- >> mm/memcontrol.c | 7 ++++--- >> 1 files changed, 4 insertions(+), 3 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 22d94f5..79f4a58 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -183,7 +183,7 @@ struct mem_cgroup_threshold { >> >> /* For threshold */ >> struct mem_cgroup_threshold_ary { >> - /* An array index points to threshold just below usage. */ >> + /* An array index points to threshold just below or equal to usage. */ >> int current_threshold; >> /* Size of entries[] */ >> unsigned int size; >> @@ -4319,14 +4319,15 @@ static int mem_cgroup_usage_register_event(struct cgroup *cgrp, >> /* Find current threshold */ >> new->current_threshold = -1; >> for (i = 0; i< size; i++) { >> - if (new->entries[i].threshold< usage) { >> + if (new->entries[i].threshold<= usage) { >> /* >> * new->current_threshold will not be used until >> * rcu_assign_pointer(), so it's safe to increment >> * it here. >> */ >> ++new->current_threshold; >> - } >> + } else >> + break; >> } >> >> /* Free old spare buffer and save old primary buffer as spare */ >> -- >> 1.7.4.1 >> -- 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