From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sha Zhengju Subject: Re: [PATCH] memcg: Free spare array to avoid memory leak Date: Thu, 08 Mar 2012 18:46:13 +0800 Message-ID: <4F588DF5.60300@gmail.com> References: <1331036004-7550-1-git-send-email-handai.szj@taobao.com> <20120307230819.GA10238@shutemov.name> <4F581554.6020801@gmail.com> <20120308103510.GA12897@shutemov.name> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; bh=+OvB1RctHh2d4/ZVtHcoSs0CUA2X1ONNj3nnV4x0ah0=; b=sXxnp+M1psIvcpcNeQv/KpzrCQZpQely2ZUjyh8aNb1DPbCfFuXOz9JzBnW+bgm9do BwbFbQTAPPzuQL5mi8nBj8LAHBX8rkptku8yE8CMOnkt0EVvGE6EZ0pNr5BygBwaGrPL 10j7NBMA8O8/umbZVHRUAGezLK0Bv4M+sJHOcf/6zeNSNa3dgDbFdGQZRJ028p24bKPE oe7vbroZRtBj+550UgOrc1M459z/4berDiyV/O4egaRmdWaPbLo/28uB73S73aM7WQQh S2CGW0mzbzBYsDIsMM/71S2R/kV2RmmpTLj03whPtcHTy90F8Fe3Jyvhb/BiHPfIfWCd ydQw== In-Reply-To: <20120308103510.GA12897-oKw7cIdHH8eLwutG50LtGA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: "Kirill A. Shutemov" Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, 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 >>>>