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

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Date:   Wed, 26 Oct 2016 14:04:03 -0400 (EDT)
From:   Bob Peterson <rpeterso@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        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

----- Original Message -----
| 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
| 
I can test it for you, if you give me about an hour.

Bob Peterson