From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail-oi0-f70.google.com (mail-oi0-f70.google.com [209.85.218.70])
	by kanga.kvack.org (Postfix) with ESMTP id 1132528070C
	for <linux-mm@kvack.org>; Tue, 22 Aug 2017 16:59:02 -0400 (EDT)
Received: by mail-oi0-f70.google.com with SMTP id a79so8986455oii.7
        for <linux-mm@kvack.org>; Tue, 22 Aug 2017 13:59:02 -0700 (PDT)
Received: from mail-oi0-x22d.google.com (mail-oi0-x22d.google.com. [2607:f8b0:4003:c06::22d])
        by mx.google.com with ESMTPS id m203si2602914oib.216.2017.08.22.13.59.01
        for <linux-mm@kvack.org>
        (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
        Tue, 22 Aug 2017 13:59:01 -0700 (PDT)
Received: by mail-oi0-x22d.google.com with SMTP id r200so62388362oie.2
        for <linux-mm@kvack.org>; Tue, 22 Aug 2017 13:59:01 -0700 (PDT)
MIME-Version: 1.0
In-Reply-To: <20170822205316.GS32112@worktop.programming.kicks-ass.net>
References: <37D7C6CF3E00A74B8858931C1DB2F07753787AE4@SHSMSX103.ccr.corp.intel.com>
 <CA+55aFxZjjqUM4kPvNEeZahPovBHFATiwADj-iPTDN0-jnU67Q@mail.gmail.com>
 <20170818185455.qol3st2nynfa47yc@techsingularity.net> <CA+55aFwX0yrUPULrDxTWVCg5c6DKh-yCG84NXVxaptXNQ4O_kA@mail.gmail.com>
 <20170821183234.kzennaaw2zt2rbwz@techsingularity.net> <37D7C6CF3E00A74B8858931C1DB2F07753788B58@SHSMSX103.ccr.corp.intel.com>
 <37D7C6CF3E00A74B8858931C1DB2F0775378A24A@SHSMSX103.ccr.corp.intel.com>
 <CA+55aFy=4y0fq9nL2WR1x8vwzJrDOdv++r036LXpR=6Jx8jpzg@mail.gmail.com>
 <37D7C6CF3E00A74B8858931C1DB2F0775378A377@SHSMSX103.ccr.corp.intel.com>
 <CA+55aFwavpFfKNW9NVgNhLggqhii-guc5aX1X5fxrPK+==id0g@mail.gmail.com> <20170822205316.GS32112@worktop.programming.kicks-ass.net>
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Tue, 22 Aug 2017 13:58:59 -0700
Message-ID: <CA+55aFxJ4x3przA6acW5qGZ-+MWSYTw0h6UjWH-D1xHcb9gnZw@mail.gmail.com>
Subject: Re: [PATCH 1/2] sched/wait: Break up long wake list walk
Content-Type: text/plain; charset="UTF-8"
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Liang, Kan" <kan.liang@intel.com>, Mel Gorman <mgorman@techsingularity.net>, Mel Gorman <mgorman@suse.de>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Tim Chen <tim.c.chen@linux.intel.com>, Ingo Molnar <mingo@elte.hu>, Andi Kleen <ak@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Johannes Weiner <hannes@cmpxchg.org>, Jan Kara <jack@suse.cz>, linux-mm <linux-mm@kvack.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

On Tue, Aug 22, 2017 at 1:53 PM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> So _the_ problem with yield() is when you hit this with a RT task it
> will busy spin and possibly not allow the task that actually has the
> lock to make progress at all.

I thought we had explicitly defined yield() to not do that.

But I guess we could make this yielding behavior depend on a few more
heuristics. So do the yield only when there is contention, and when
it's a non-RT task.

          Linus

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>