From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 420A9C433DF for ; Fri, 15 May 2020 08:20:17 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F2F5A206F4 for ; Fri, 15 May 2020 08:20:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F2F5A206F4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A3F0D90000C; Fri, 15 May 2020 04:20:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9EF338E0005; Fri, 15 May 2020 04:20:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9032090000C; Fri, 15 May 2020 04:20:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0226.hostedemail.com [216.40.44.226]) by kanga.kvack.org (Postfix) with ESMTP id 7641F8E0005 for ; Fri, 15 May 2020 04:20:16 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 3A8214DD9 for ; Fri, 15 May 2020 08:20:16 +0000 (UTC) X-FDA: 76818256032.05.wind32_76b0c08f83c49 X-HE-Tag: wind32_76b0c08f83c49 X-Filterd-Recvd-Size: 4603 Received: from huawei.com (szxga07-in.huawei.com [45.249.212.35]) by imf46.hostedemail.com (Postfix) with ESMTP for ; Fri, 15 May 2020 08:20:15 +0000 (UTC) Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 549A62D7613678341757; Fri, 15 May 2020 16:20:08 +0800 (CST) Received: from [10.133.206.78] (10.133.206.78) by smtp.huawei.com (10.3.19.206) with Microsoft SMTP Server (TLS) id 14.3.487.0; Fri, 15 May 2020 16:20:05 +0800 Subject: Re: [PATCH v2] memcg: Fix memcg_kmem_bypass() for remote memcg charging To: Michal Hocko , Roman Gushchin CC: Johannes Weiner , Vladimir Davydov , Cgroups , , Andrew Morton , Shakeel Butt References: <20200513090502.GV29153@dhcp22.suse.cz> <76f71776-d049-7407-8574-86b6e9d80704@huawei.com> <20200513112905.GX29153@dhcp22.suse.cz> <3a721f62-5a66-8bc5-247b-5c8b7c51c555@huawei.com> <20200513161110.GA70427@carbon.DHCP.thefacebook.com> <20e89344-cf00-8b0c-64c3-0ac7efd601e6@huawei.com> <20200514225259.GA81563@carbon.dhcp.thefacebook.com> <20200515065645.GD29153@dhcp22.suse.cz> From: Zefan Li Message-ID: Date: Fri, 15 May 2020 16:20:04 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: <20200515065645.GD29153@dhcp22.suse.cz> Content-Type: text/plain; charset="gbk" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.133.206.78] X-CFilter-Loop: Reflected X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2020/5/15 14:56, Michal Hocko wrote: > On Thu 14-05-20 15:52:59, Roman Gushchin wrote: >> On Thu, May 14, 2020 at 09:16:29AM +0800, Zefan Li wrote: >>> On 2020/5/14 0:11, Roman Gushchin wrote: >>>> On Wed, May 13, 2020 at 07:47:49PM +0800, Zefan Li wrote: >>>>> While trying to use remote memcg charging in an out-of-tree kernel module >>>>> I found it's not working, because the current thread is a workqueue thread. >>>>> >>>>> As we will probably encounter this issue in the future as the users of >>>>> memalloc_use_memcg() grow, it's better we fix it now. >>>>> >>>>> Signed-off-by: Zefan Li >>>>> --- >>>>> >>>>> v2: add a comment as sugguested by Michal. and add changelog to explain why >>>>> upstream kernel needs this fix. >>>>> >>>>> --- >>>>> >>>>> mm/memcontrol.c | 3 +++ >>>>> 1 file changed, 3 insertions(+) >>>>> >>>>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >>>>> index a3b97f1..43a12ed 100644 >>>>> --- a/mm/memcontrol.c >>>>> +++ b/mm/memcontrol.c >>>>> @@ -2802,6 +2802,9 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg, >>>>> >>>>> static inline bool memcg_kmem_bypass(void) >>>>> { >>>>> + /* Allow remote memcg charging in kthread contexts. */ >>>>> + if (unlikely(current->active_memcg)) >>>>> + return false; >>>>> if (in_interrupt() || !current->mm || (current->flags & PF_KTHREAD)) >>>>> return true; >>>> >>>> Shakeel is right about interrupts. How about something like this? >>>> >>>> static inline bool memcg_kmem_bypass(void) >>>> { >>>> if (in_interrupt()) >>>> return true; >>>> >>>> if ((!current->mm || current->flags & PF_KTHREAD) && !current->active_memcg) >>>> return true; >>>> >>>> return false; >>>> } >>>> >>> >>> I thought the user should ensure not do this, but now I think it makes sense to just bypass >>> the interrupt case. >> >> I think now it's mostly a legacy of the opt-out kernel memory accounting. >> Actually we can relax this requirement by forcibly overcommit the memory cgroup >> if the allocation is happening from the irq context, and punish it afterwards. >> Idk how much we wanna this, hopefully nobody is allocating large non-temporarily >> objects from an irq. > > I do not think we want to pretend that remote charging from the IRQ > context is supported. Why don't we simply WARN_ON(in_interrupt()) there? > How about: static inline bool memcg_kmem_bypass(void) { if (in_interrupt()) { WARN_ON(current->active_memcg); return true; } /* Allow remote memcg charging in kthread contexts. */ if ((!current->mm || (current->flags & PF_KTHREAD)) && !current->active_memcg) return true; return false; } From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zefan Li Subject: Re: [PATCH v2] memcg: Fix memcg_kmem_bypass() for remote memcg charging Date: Fri, 15 May 2020 16:20:04 +0800 Message-ID: References: <20200513090502.GV29153@dhcp22.suse.cz> <76f71776-d049-7407-8574-86b6e9d80704@huawei.com> <20200513112905.GX29153@dhcp22.suse.cz> <3a721f62-5a66-8bc5-247b-5c8b7c51c555@huawei.com> <20200513161110.GA70427@carbon.DHCP.thefacebook.com> <20e89344-cf00-8b0c-64c3-0ac7efd601e6@huawei.com> <20200514225259.GA81563@carbon.dhcp.thefacebook.com> <20200515065645.GD29153@dhcp22.suse.cz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20200515065645.GD29153-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Michal Hocko , Roman Gushchin Cc: Johannes Weiner , Vladimir Davydov , Cgroups , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Andrew Morton , Shakeel Butt On 2020/5/15 14:56, Michal Hocko wrote: > On Thu 14-05-20 15:52:59, Roman Gushchin wrote: >> On Thu, May 14, 2020 at 09:16:29AM +0800, Zefan Li wrote: >>> On 2020/5/14 0:11, Roman Gushchin wrote: >>>> On Wed, May 13, 2020 at 07:47:49PM +0800, Zefan Li wrote: >>>>> While trying to use remote memcg charging in an out-of-tree kernel module >>>>> I found it's not working, because the current thread is a workqueue thread. >>>>> >>>>> As we will probably encounter this issue in the future as the users of >>>>> memalloc_use_memcg() grow, it's better we fix it now. >>>>> >>>>> Signed-off-by: Zefan Li >>>>> --- >>>>> >>>>> v2: add a comment as sugguested by Michal. and add changelog to explain why >>>>> upstream kernel needs this fix. >>>>> >>>>> --- >>>>> >>>>> mm/memcontrol.c | 3 +++ >>>>> 1 file changed, 3 insertions(+) >>>>> >>>>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >>>>> index a3b97f1..43a12ed 100644 >>>>> --- a/mm/memcontrol.c >>>>> +++ b/mm/memcontrol.c >>>>> @@ -2802,6 +2802,9 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg, >>>>> >>>>> static inline bool memcg_kmem_bypass(void) >>>>> { >>>>> + /* Allow remote memcg charging in kthread contexts. */ >>>>> + if (unlikely(current->active_memcg)) >>>>> + return false; >>>>> if (in_interrupt() || !current->mm || (current->flags & PF_KTHREAD)) >>>>> return true; >>>> >>>> Shakeel is right about interrupts. How about something like this? >>>> >>>> static inline bool memcg_kmem_bypass(void) >>>> { >>>> if (in_interrupt()) >>>> return true; >>>> >>>> if ((!current->mm || current->flags & PF_KTHREAD) && !current->active_memcg) >>>> return true; >>>> >>>> return false; >>>> } >>>> >>> >>> I thought the user should ensure not do this, but now I think it makes sense to just bypass >>> the interrupt case. >> >> I think now it's mostly a legacy of the opt-out kernel memory accounting. >> Actually we can relax this requirement by forcibly overcommit the memory cgroup >> if the allocation is happening from the irq context, and punish it afterwards. >> Idk how much we wanna this, hopefully nobody is allocating large non-temporarily >> objects from an irq. > > I do not think we want to pretend that remote charging from the IRQ > context is supported. Why don't we simply WARN_ON(in_interrupt()) there? > How about: static inline bool memcg_kmem_bypass(void) { if (in_interrupt()) { WARN_ON(current->active_memcg); return true; } /* Allow remote memcg charging in kthread contexts. */ if ((!current->mm || (current->flags & PF_KTHREAD)) && !current->active_memcg) return true; return false; }