linux-kernel - Re: Q. drm/i915 shrinker, synchronize_rcu

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Date:   Wed, 10 May 2017 14:01:37 +0300
From:   Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
To:     Andrea Arcangeli <aarcange@...hat.com>,
        Hugh Dickins <hughd@...gle.com>
Cc:     "J. R. Okajima" <hooanon05g@...il.com>, chris@...is-wilson.co.uk,
        daniel.vetter@...ll.ch, jani.nikula@...el.com,
        linux-kernel@...r.kernel.org
Subject: Re: Q. drm/i915 shrinker, synchronize_rcu_expedited() from handlers

On ke, 2017-05-10 at 12:43 +0200, Andrea Arcangeli wrote:
> It works for me too. I'm running my workstation also with
> synchronize_rcu removed from i915_gem_shrink_all in addition to the
> above. Isn't the oom method invoked from reclaim context too? As far
> as I can tell synchronize_rcu can end up throttling on a background
> synchronize_rcu_expedited(), so it might end up in the same issue
> unless removed too.

Thanks for testing and spotting my bad grepping, I'll add your T-b and
s
end v3.

Regards, Joonas

> Tested-by: Andrea Arcangeli <aarcange@...hat.com>
> 
> (I can't reproduce the lockups 100% of the time, but they never
> happened again with this patch and I happened to run the load that
> reproduces them a couple of times already with v4.11 and this patch
> applied)
> 
> It's also certainly improving performance by removing the
> synchronize_rcu_expedited from the _count methods where it was useless
> (in addition to unsafe).
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation