From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx187.postini.com [74.125.245.187]) by kanga.kvack.org (Postfix) with SMTP id 1677D6B13F0 for ; Thu, 2 Feb 2012 06:08:47 -0500 (EST) Received: by iagz16 with SMTP id z16so4223798iag.14 for ; Thu, 02 Feb 2012 03:08:46 -0800 (PST) Message-ID: <4F2A6EBC.5090207@gmail.com> Date: Thu, 02 Feb 2012 19:08:44 +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> <4F2A6B5F.3090303@gmail.com> In-Reply-To: <4F2A6B5F.3090303@gmail.com> 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 06:54 PM, Sha Zhengju wrote: > 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 Err.. Sorry for showing inaccurate index position... (may because of the mail format) now: threshold array: 3 [5] 7 9 (usage = 6, index = 5) next turn: threshold array: 3 5 [7] 9 (usage = 7, index = 7) after registering a new event(threshold = 10): threshold array: 3 [5] 7 9 10 (usage = 7, index = 5) >>> 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