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charset="UTF-8" ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657159775; a=rsa-sha256; cv=none; b=MK3henRbRxKtVTZp0zi2mcj55VoiuWOqopdARmwLk5Syfzx7O5tjJDSMWIqJizM5iywksz VemvIsC6D0TAzd28R9lJH8+bmrsx05Ys3qKsm91s1TL2FdAI6A+1dFOADFkmt5uTG0tQ69 doYKqyK6w4pxy9GzDY3J8YY36EMqR6w= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=jI2x4p7w; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf27.hostedemail.com: domain of alexei.starovoitov@gmail.com designates 209.85.218.45 as permitted sender) smtp.mailfrom=alexei.starovoitov@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657159775; 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=kGIHS1Q8whoejLOanjZ8Dl2VaVkwGN34JapXBn0P4vU=; b=d/y5k15iM9YFfOpO4Znkob0csIdJRtsdZs94TkefQ5luPW8ao8jmE88PWysPccf73A6f+S xJ6yUKspprA2HdGLrgd4YoMZTcQUvMZqkyZm12urCCEQ+g9kxefCs9FPViUM9g+9RLwLUj 77kIaRgfzhPwxmB2Qz/DnPDg+ihXywc= X-Rspamd-Server: rspam04 X-Rspam-User: Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=jI2x4p7w; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf27.hostedemail.com: domain of alexei.starovoitov@gmail.com designates 209.85.218.45 as permitted sender) smtp.mailfrom=alexei.starovoitov@gmail.com X-Stat-Signature: zga4w1pobpqfdxsm7erxa1wxxzpo6gjk X-Rspamd-Queue-Id: 931734001B X-HE-Tag: 1657159775-641525 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 Wed, Jul 6, 2022 at 5:25 PM Roman Gushchin wrote: > > On Thu, Jul 07, 2022 at 12:07:21AM +0000, Shakeel Butt wrote: > > On Wed, Jul 06, 2022 at 03:58:47PM +0000, Yafang Shao wrote: > > > GFP_ATOMIC doesn't cooperate well with memcg pressure so far, especially > > > if we allocate too much GFP_ATOMIC memory. For example, when we set the > > > memcg limit to limit a non-preallocated bpf memory, the GFP_ATOMIC can > > > easily break the memcg limit by force charge. So it is very dangerous to > > > use GFP_ATOMIC in non-preallocated case. One way to make it safe is to > > > remove __GFP_HIGH from GFP_ATOMIC, IOW, use (__GFP_ATOMIC | > > > __GFP_KSWAPD_RECLAIM) instead, then it will be limited if we allocate > > > too much memory. > > > > Please use GFP_NOWAIT instead of (__GFP_ATOMIC | __GFP_KSWAPD_RECLAIM). > > There is already a plan to completely remove __GFP_ATOMIC and mm-tree > > already have a patch for that. > > Oh, I didn't know this, thanks for heads up! > I agree that GFP_NOWAIT is the best choice then. > > Btw, we probably shouldn't even add GFP_NOWAIT if the allocation is performed > from the bpf syscall context. Why would we fail to pre-allocate a map if > we can easily go into the reclaim? But probably better to leave it for > a separate change. The places affected by this patch are in atomic context. Prealloc path from syscall is using GFP_USER.