linux-kernel - Re: [PATCH 5/5] i915: fence workqueue optimization

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Message-ID: <20170407095838.GF10496@nuc-i3427.alporthouse.com>
Date:   Fri, 7 Apr 2017 10:58:38 +0100
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Andrea Arcangeli <aarcange@...hat.com>
Cc:     Martin Kepplinger <martink@...teo.de>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        daniel.vetter@...el.com, Dave Airlie <airlied@...il.com>,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 5/5] i915: fence workqueue optimization

On Fri, Apr 07, 2017 at 01:23:47AM +0200, Andrea Arcangeli wrote:
> Insist to run llist_del_all() until the free_list is found empty, this
> may avoid having to schedule more workqueues.

The work will already be scheduled (everytime we add the first element,
the work is scheduled, and the scheduled bit is cleared before the work
is executed). So we aren't saving the kworker from having to process
another work, but we may make that having nothing to do. The question is
whether we want to trap the kworker here, and presumably you will also want
to add a cond_resched() between passes.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre