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AJvYcCU65VQKH0UO/LnvPVxwS46+in7rU7rQZkOy2mNKHv21GyUv9PcPtv4kxiB36mcGw0shsj5IDR70vw==@kvack.org X-Gm-Message-State: AOJu0YxKxq7ufkqQoL0hMinyA9WwwSyGEqYLaqB4rmSxGtwMvYwP/xSf 06PbX6JjBUI6rb7KwXZTSXwNxozbsG+nP6DXP16d+1LD+7dwuoiAXML4Wth36fEF90Zw3q0V2ue vIlDvFWjzrAs0uxa3pJudd+2o10HPtTnvFs0a X-Google-Smtp-Source: AGHT+IELhCgaynS2p5jCPKBt9DwSqWQGFp6VZtRDsoydaZOboxj7g8bI6VTkVAmCJB8RPjES11D4UGwAuYkbqMFWR+s= X-Received: by 2002:a05:6102:3583:b0:4a4:8b67:4f73 with SMTP id ada2fe7eead31-4a48b675218mr4072774137.7.1728949275818; Mon, 14 Oct 2024 16:41:15 -0700 (PDT) MIME-Version: 1.0 References: <20241014221211.832591-1-weixugc@google.com> <20241014162541.a3049d0824a2f9b22221c17a@linux-foundation.org> In-Reply-To: <20241014162541.a3049d0824a2f9b22221c17a@linux-foundation.org> From: Wei Xu Date: Mon, 14 Oct 2024 16:41:03 -0700 Message-ID: Subject: Re: [PATCH 1/2] mm/mglru: only clear kswapd_failures if reclaimable To: Andrew Morton Cc: Yu Zhao , Axel Rasmussen , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 6z64xw4gy47xygocddoxpy8u99gcahzz X-Rspamd-Queue-Id: 6583180006 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1728949264-678483 X-HE-Meta: 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 38hlS0Hy YFUSk2in6nZy0xGgCEWk+YCqAfpeQL30zlOhBBSMRJ54t0JwtgYE46qN/q9c2PWoLO254BTt63hOwf1YCmncWzlv0n7SEq6I0G370W0QZJxbZVf8RzBvE8dGlUuV7jFyaw5pjANZ5bTsBkl0hbNY5dP+Efg7zLFLx8yMsw8aBDyZ2qECwM/IgPjyzDtILxoo77YGUkMGXqK0HzadxqVbiyx3zLTyZhZza3dIOrDbRGDcCaQlv2ccjJrziOsGHueJgRhXXzQgBSaodYleNVLLqudymoR1MWGFOf87dggAIkjlFyZPKbAfNxxN3rO3ub97cvOTq X-Bogosity: Ham, tests=bogofilter, spamicity=0.000553, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Oct 14, 2024 at 4:25=E2=80=AFPM Andrew Morton wrote: > > On Mon, 14 Oct 2024 22:12:11 +0000 Wei Xu wrote: > > > lru_gen_shrink_node() unconditionally clears kswapd_failures, which > > can prevent kswapd from sleeping and cause 100% kswapd cpu usage even > > when kswapd repeatedly fails to make progress in reclaim. > > > > Only clear kswap_failures in lru_gen_shrink_node() if reclaim makes > > some progress, similar to shrink_node(). > > That sounds bad. What triggers this? Can you suggest why it has just > bee discovered, after 1.5 years? And should the fix be backported into > -stable kernels? > I happened to run into this problem in one of my tests recently. It requires a combination of several conditions: The allocator needs to allocate a right amount of pages such that it can wake up kswapd without itself being OOM killed; there is no memory for kswapd to reclaim (My test disables swap and cleans page cache first); no other process frees enough memory at the same time. I think the fix is a good candidate for stable kernels.