From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by kanga.kvack.org (Postfix) with ESMTP id 248FE8E0033 for ; Mon, 17 Dec 2018 20:15:06 -0500 (EST) Received: by mail-wr1-f69.google.com with SMTP id h11so4686887wrs.2 for ; Mon, 17 Dec 2018 17:15:06 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id v23sor1424977wrd.4.2018.12.17.17.15.04 for (Google Transport Security); Mon, 17 Dec 2018 17:15:04 -0800 (PST) MIME-Version: 1.0 References: <20181214171508.7791-1-surenb@google.com> <20181214171508.7791-5-surenb@google.com> <20181217155525.GC2218@hirez.programming.kicks-ass.net> In-Reply-To: <20181217155525.GC2218@hirez.programming.kicks-ass.net> From: Suren Baghdasaryan Date: Mon, 17 Dec 2018 17:14:53 -0800 Message-ID: Subject: Re: [PATCH 4/6] psi: introduce state_mask to represent stalled psi states Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Greg Kroah-Hartman , Tejun Heo , lizefan@huawei.com, Johannes Weiner , axboe@kernel.dk, dennis@kernel.org, Dennis Zhou , Ingo Molnar , Andrew Morton , Jonathan Corbet , cgroups@vger.kernel.org, linux-mm , linux-doc@vger.kernel.org, LKML , kernel-team@android.com On Mon, Dec 17, 2018 at 7:55 AM Peter Zijlstra wrote: > > On Fri, Dec 14, 2018 at 09:15:06AM -0800, Suren Baghdasaryan wrote: > > The psi monitoring patches will need to determine the same states as > > record_times(). To avoid calculating them twice, maintain a state mask > > that can be consulted cheaply. Do this in a separate patch to keep the > > churn in the main feature patch at a minimum. > > > > Signed-off-by: Suren Baghdasaryan > > --- > > include/linux/psi_types.h | 3 +++ > > kernel/sched/psi.c | 29 +++++++++++++++++++---------- > > 2 files changed, 22 insertions(+), 10 deletions(-) > > > > diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h > > index 2cf422db5d18..2c6e9b67b7eb 100644 > > --- a/include/linux/psi_types.h > > +++ b/include/linux/psi_types.h > > @@ -53,6 +53,9 @@ struct psi_group_cpu { > > /* States of the tasks belonging to this group */ > > unsigned int tasks[NR_PSI_TASK_COUNTS]; > > > > + /* Aggregate pressure state derived from the tasks */ > > + u32 state_mask; > > + > > /* Period time sampling buckets for each state of interest (ns) */ > > u32 times[NR_PSI_STATES]; > > > > Since we spend so much time counting space in that line, maybe add a > note to the Changlog about how this fits. Will do. > Also, since I just had to re-count, you might want to add explicit > numbers to the psi_res and psi_states enums. Sounds reasonable. > > + if (state_mask & (1 << s)) > > We have the BIT() macro, but I'm honestly not sure that will improve > things. I was mimicking the rest of the code in psi.c that uses this kind of bit masking. Can change if you think that would be better.