From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [RFC PATCH 10/10] psi: aggregate ongoing stall events when somebody reads pressure Date: Thu, 12 Jul 2018 16:45:37 -0700 Message-ID: <20180712164537.324caee21fd68c47a02af009@linux-foundation.org> References: <20180712172942.10094-1-hannes@cmpxchg.org> <20180712172942.10094-11-hannes@cmpxchg.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180712172942.10094-11-hannes@cmpxchg.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Johannes Weiner Cc: Ingo Molnar , Peter Zijlstra , Linus Torvalds , Tejun Heo , Suren Baghdasaryan , Vinayak Menon , Christopher Lameter , Mike Galbraith , Shakeel Butt , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com On Thu, 12 Jul 2018 13:29:42 -0400 Johannes Weiner wrote: > Right now, psi reports pressure and stall times of already concluded > stall events. For most use cases this is current enough, but certain > highly latency-sensitive applications, like the Android OOM killer, > might want to know about and react to stall states before they have > even concluded (e.g. a prolonged reclaim cycle). > > This patches the procfs/cgroupfs interface such that when the pressure > metrics are read, the current per-cpu states, if any, are taken into > account as well. > > Any ongoing states are concluded, their time snapshotted, and then > restarted. This requires holding the rq lock to avoid corruption. It > could use some form of rq lock ratelimiting or avoidance. > > Requested-by: Suren Baghdasaryan > Not-yet-signed-off-by: Johannes Weiner What-does-that-mean:?