linux-kernel - RE: [PATCH] kfence: use TASK_IDLE when awaiting allocation

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Date:   Fri, 21 May 2021 09:39:01 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Marco Elver' <elver@...gle.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
CC:     "glider@...gle.com" <glider@...gle.com>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        Mel Gorman <mgorman@...e.de>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH] kfence: use TASK_IDLE when awaiting allocation

From: Marco Elver
> Sent: 21 May 2021 09:32
> 
> Since wait_event() uses TASK_UNINTERRUPTIBLE by default, waiting for an
> allocation counts towards load. However, for KFENCE, this does not make
> any sense, since there is no busy work we're awaiting.
> 
> Instead, use TASK_IDLE via wait_event_idle() to not count towards load.

Doesn't that let the process be interruptible by a signal.
Which is probably not desirable.

There really ought to be a way of sleeping with TASK_UNINTERRUPTIBLE
without changing the load-average.

IIRC the load-average is really intended to include processes
that are waiting for disk - especially for swap.

	David

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