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From: Roman Gushchin To: Shakeel Butt Cc: Andrew Morton , Yafang Shao , Johannes Weiner , Michal Hocko , Muchun Song , Cgroups , Linux MM , bpf Subject: Re: [PATCH] mm: memcontrol: do not miss MEMCG_MAX events for enforced allocations Message-ID: References: <20220702033521.64630-1-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=HIxjJQ6k; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf13.hostedemail.com: domain of roman.gushchin@linux.dev designates 188.165.223.204 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656776360; a=rsa-sha256; cv=none; b=AxC6lsY754MPK0gCebhQr/quYZG6MPGYLpc839PlQA2onMbFFzViDier8/iQBY/Q1Ozo0E Vpng+a7zxbZOJIwnC4OMlz0tlx3bsuU40RrOBkiUI6PiEQbYDlLzI8kJnT0kruObXwUnqL V8+Wt/8IOQClIkC/t/XSZXTMKHjt+SY= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656776360; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=9Mn01W+SjwBjTn12n10GHRZZyUQBH10vGdvggjcJ1qs=; b=OnJRYtUdw5JJYHhVwdAmkkUfwAgoYnYTQwUfrvJ+dXpi4rX+WDbfoSqfgMy+OXobHNXJIJ wW9aoWeWXTH0SfFLat42o+OPzpBn+J0oM11z8okOm5KdWRe5ogmKhcy98ZGi4lPq3IJMA7 keszTqlBFTEOjtkKzRGaU0GWTSBwOXA= X-Rspam-User: Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=HIxjJQ6k; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf13.hostedemail.com: domain of roman.gushchin@linux.dev designates 188.165.223.204 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 662AF20032 X-Stat-Signature: 7yqbuwqg1pnznxrm9bzo1jtfp9sye9au X-HE-Tag: 1656776360-827003 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 Fri, Jul 01, 2022 at 10:50:40PM -0700, Shakeel Butt wrote: > On Fri, Jul 1, 2022 at 8:35 PM Roman Gushchin wrote: > > > > Yafang Shao reported an issue related to the accounting of bpf > > memory: if a bpf map is charged indirectly for memory consumed > > from an interrupt context and allocations are enforced, MEMCG_MAX > > events are not raised. > > > > It's not/less of an issue in a generic case because consequent > > allocations from a process context will trigger the reclaim and > > MEMCG_MAX events. However a bpf map can belong to a dying/abandoned > > memory cgroup, so it might never happen. > > The patch looks good but the above sentence is confusing. What might > never happen? Reclaim or MAX event on dying memcg? Direct reclaim and MAX events. I agree it might be not clear without looking into the code. How about something like this? "It's not/less of an issue in a generic case because consequent allocations from a process context will trigger the direct reclaim and MEMCG_MAX events will be raised. However a bpf map can belong to a dying/abandoned memory cgroup, so there will be no allocations from a process context and no MEMCG_MAX events will be triggered." Thanks!