From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Down Subject: Re: [PATCH] mm: memcontrol: restore proper dirty throttling when memory.high changes Date: Tue, 28 Jul 2020 15:07:11 +0100 Message-ID: <20200728140711.GA196042@chrisdown.name> References: <20200728135210.379885-1-hannes@cmpxchg.org> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=QDO5xtNZ22C72a1tBmEqwRX/00TFY7M8B1T43bXeDoo=; b=SLaBgESU+1xIJqSNqhieu03SNXKyKL+9MH8hgBEP20Gv4XC0tv7Aigf51SuYFDsJ0+ 09GIRi4cOnfUbvnWrtl2Bj6Hz1USuSfKPbNvwk6y0GavN4M4MAnesqzHkieumXy0qARA QDirQJmvwSNdLa088Smv1pEnZ7tVhoCsP9bwM= Content-Disposition: inline In-Reply-To: <20200728135210.379885-1-hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" Content-Transfer-Encoding: 7bit To: Johannes Weiner Cc: Andrew Morton , Michal Hocko , Roman Gushchin , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org Johannes Weiner writes: >Commit 8c8c383c04f6 ("mm: memcontrol: try harder to set a new >memory.high") inadvertently removed a callback to recalculate the >writeback cache size in light of a newly configured memory.high limit. > >Without letting the writeback cache know about a potentially heavily >reduced limit, it may permit too many dirty pages, which can cause >unnecessary reclaim latencies or even avoidable OOM situations. > >This was spotted while reading the code, it hasn't knowingly caused >any problems in practice so far. > >Fixes: 8c8c383c04f6 ("mm: memcontrol: try harder to set a new memory.high") >Signed-off-by: Johannes Weiner Acked-by: Chris Down