linux-kernel - Re: CONFIG_VMAP_STACK, on-stack struct, and wake_up

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Date:   Wed, 26 Oct 2016 10:58:01 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Andreas Gruenbacher <agruenba@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bob Peterson <rpeterso@...hat.com>,
        Steven Whitehouse <swhiteho@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        linux-mm <linux-mm@...ck.org>
Subject: Re: CONFIG_VMAP_STACK, on-stack struct, and wake_up_bit

On Wed, Oct 26, 2016 at 10:15 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Oh, and the patch is obviously entirely untested. I wouldn't want to
> ruin my reputation by *testing* the patches I send out. What would be
> the fun in that?

So I tested it. It compiles, and it actually also solves the
performance problem I was complaining about a couple of weeks ago with
"unlock_page()" having an insane 3% CPU overhead when doing lots of
small script ("make -j16 test" in the git tree for those that weren't
involved in the original thread three weeks ago).

So quite frankly, I'll just commit it. It should fix the new problem
with gfs2 and CONFIG_VMAP_STACK, and I see no excuse for the crazy
zone stuff considering how harmful it is to everybody else.

I expect that when the NUMA people complain about page locking (if
they ever even notice), PeterZ will stand up like the hero he is, and
say "look here, I can solve this for you".

                    Linus