Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.34 as permitted sender) client-ip=23.128.96.34;
MIME-Version: 1.0
References: <20231005161727.1855004-1-joel@joelfernandes.org> <98d06022-accd-a1df-7608-dcd6689b44ec@linux.vnet.ibm.com>
In-Reply-To: <98d06022-accd-a1df-7608-dcd6689b44ec@linux.vnet.ibm.com>
From:   Vineeth Pillai <vineethrp@google.com>
Date:   Fri, 6 Oct 2023 17:20:41 -0400
Message-ID: <CA+HDTgSnab1eTWkFX-E9Yjvd8R3Apw4PyqbBHnYYg246Va1zYA@mail.gmail.com>
Subject: Re: [PATCH RFC] sched/fair: Avoid unnecessary IPIs for ILB
To:     Shrikanth Hegde <sshegde@linux.vnet.ibm.com>
Cc:     "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        Suleiman Souhlal <suleiman@google.com>,
        Hsin Yi <hsinyi@google.com>,
        Frederic Weisbecker <frederic@kernel.org>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Valentin Schneider <vschneid@redhat.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Shrikanth,

> Hi Joel/Vineeth.
>
> Its an interesting patch.
>
> Gave this patch a try on powerpc system with 96 CPU. (12 cores SMT8)
> Was debugging an issue where ILB count goes up significantly at a specific
> busy CPU count. Haven't yet found out why. Its WIP. Was curious if this patch
> would address that issue.
>
Increased SCHED_SOFTIRQ was another problem that we noticed and we
have a separate fix for that in the chromeos tree. We were planning to
send the patch after a bit more testing. You could try the patch and
see if it solves the problem that you are seeing:
https://chromium.googlesource.com/chromiumos/third_party/kernel/+/918f229ba2ff720f5dfae4768469acbb6ea39fe2

Thanks