From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx179.postini.com [74.125.245.179]) by kanga.kvack.org (Postfix) with SMTP id 98B166B002C for ; Thu, 8 Mar 2012 05:46:17 -0500 (EST) Received: by pbcup15 with SMTP id up15so1622846pbc.14 for ; Thu, 08 Mar 2012 02:46:16 -0800 (PST) Message-ID: <4F588DF5.60300@gmail.com> Date: Thu, 08 Mar 2012 18:46:13 +0800 From: Sha Zhengju MIME-Version: 1.0 Subject: Re: [PATCH] memcg: Free spare array to avoid memory leak References: <1331036004-7550-1-git-send-email-handai.szj@taobao.com> <20120307230819.GA10238@shutemov.name> <4F581554.6020801@gmail.com> <20120308103510.GA12897@shutemov.name> In-Reply-To: <20120308103510.GA12897@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.hiroyu@jp.fujitsu.com, Sha Zhengju On 03/08/2012 06:35 PM, Kirill A. Shutemov wrote: > On Thu, Mar 08, 2012 at 10:11:32AM +0800, Sha Zhengju wrote: >> On 03/08/2012 07:08 AM, Kirill A. Shutemov wrote: >>> On Tue, Mar 06, 2012 at 08:13:24PM +0800, Sha Zhengju wrote: >>>> From: Sha Zhengju >>>> >>>> When the last event is unregistered, there is no need to keep the spare >>>> array anymore. So free it to avoid memory leak. >>> It's not a leak. It will be freed on next event register. >> >> Yeah, I noticed that. But what if it is just the last one and no more >> event registering ? > See my question below. ;) > >>> Yeah, we don't have to keep spare if primary is empty. But is it worth to >>> make code more complicated to save few bytes of memory? >>> If we unregister the last event and *don't* register a new event anymore, the primary is freed but the spare is still kept which has no chance to free. IMHO, it's obvious not a problem of saving bytes but *memory leak*. >>>> Signed-off-by: Sha Zhengju >>>> >>>> --- >>>> mm/memcontrol.c | 6 ++++++ >>>> 1 files changed, 6 insertions(+), 0 deletions(-) >>>> >>>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >>>> index 22d94f5..3c09a84 100644 >>>> --- a/mm/memcontrol.c >>>> +++ b/mm/memcontrol.c >>>> @@ -4412,6 +4412,12 @@ static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp, >>>> swap_buffers: >>>> /* Swap primary and spare array */ >>>> thresholds->spare = thresholds->primary; >>>> + /* If all events are unregistered, free the spare array */ >>>> + if (!new) { >>>> + kfree(thresholds->spare); >>>> + thresholds->spare = NULL; >>>> + } >>>> + >>>> rcu_assign_pointer(thresholds->primary, new); >>>> >>>> /* To be sure that nobody uses thresholds */ >>>> -- >>>> 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