linux-kernel - Re: [PATCH tip/sched/core] sched/fair: Make balance_fair() test sched_fair_runnable() instead of rq->nr

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Message-ID: <ZrET6XFqxkMYjVpY@slm.duckdns.org>
Date: Mon, 5 Aug 2024 08:03:21 -1000
From: Tejun Heo <tj@...nel.org>
To: K Prateek Nayak <kprateek.nayak@....com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	linux-kernel@...r.kernel.org, kernel-team@...a.com,
	David Vernet <void@...ifault.com>
Subject: Re: [PATCH tip/sched/core] sched/fair: Make balance_fair() test
 sched_fair_runnable() instead of rq->nr_running

Hello,

On Mon, Aug 05, 2024 at 08:51:05AM +0530, K Prateek Nayak wrote:
...
> When does this happen exactly? throttle_cfs_rq() calls sub_nr_running()
> negating the "h_nr_running" of the throttled entity from the
> rq->nr_running. Even deadline entities on being throttled dequeue the
> entity (or don't enqueue them at all in enqueue_dl_entity()) and would
> have the correct "rq->nr_running". Could you please highlight the path
> that might hit this scenario?

I just missed the sub_nr_running() call. No wonder I couldn't see behavior
difference. I'll redo the patch description.

Thanks.

-- 
tejun