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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id f83sm841590qke.80.2019.09.03.08.42.23 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 03 Sep 2019 08:42:24 -0700 (PDT) Message-ID: <1567525342.5576.60.camel@lca.pw> Subject: Re: [PATCH] net/skbuff: silence warnings under memory pressure From: Qian Cai To: Michal Hocko , Eric Dumazet Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Tue, 03 Sep 2019 11:42:22 -0400 In-Reply-To: <20190903132231.GC18939@dhcp22.suse.cz> References: <1567177025-11016-1-git-send-email-cai@lca.pw> <6109dab4-4061-8fee-96ac-320adf94e130@gmail.com> <1567178728.5576.32.camel@lca.pw> <229ebc3b-1c7e-474f-36f9-0fa603b889fb@gmail.com> <20190903132231.GC18939@dhcp22.suse.cz> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit 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 Tue, 2019-09-03 at 15:22 +0200, Michal Hocko wrote: > On Fri 30-08-19 18:15:22, Eric Dumazet wrote: > > If there is a risk of flooding the syslog, we should fix this generically > > in mm layer, not adding hundred of __GFP_NOWARN all over the places. > > We do already ratelimit in warn_alloc. If it isn't sufficient then we > can think of a different parameters. Or maybe it is the ratelimiting > which doesn't work here. Hard to tell and something to explore. The time-based ratelimit won't work for skb_build() as when a system under memory pressure, and the CPU is fast and IO is so slow, it could take a long time to swap and trigger OOM. I suppose what happens is those skb_build() allocations are from softirq, and once one of them failed, it calls printk() which generates more interrupts. Hence, the infinite loop.