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From: Mike Galbraith <efault@gmx.de>
To: Venkatesh Pallipadi <venki@google.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org, Paul Turner <pjt@google.com>,
Nick Piggin <npiggin@gmail.com>
Subject: Re: [PATCH 3/3] sched: newidle balance set idle_timestamp only on successful pull
Date: Wed, 09 Feb 2011 04:37:21 +0100 [thread overview]
Message-ID: <1297222641.8035.4.camel@marge.simson.net> (raw)
In-Reply-To: <1297188819-19999-4-git-send-email-venki@google.com>
On Tue, 2011-02-08 at 10:13 -0800, Venkatesh Pallipadi wrote:
> load_balance() could return a negative value in the case of
> SMT sibling CPU being busy. Code in idle_balance() though, uses this
> return value as an indicator of successful task pull, ignoring the
> -1 return value.
Yup, garden variety bug.
> This has two problems:
> 1) Resets idle_stamp even when this return value is -1.
> Specific case is on SMT capable system, CPU A is idle and its sibling
> CPU B is busy. In this case, CPU A avg_idle will not depend on
> a task sleeping/waking up on it. Instead it will continue to hold stale
> avg_idle value for extended period of time.
Not good.
Acked-by: Mike Galbraith <efault@gmx.de>
-Mike
next prev parent reply other threads:[~2011-02-09 3:37 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-04 20:51 [PATCH] sched: Resolve sd_idle and first_idle_cpu Catch-22 Venkatesh Pallipadi
2011-02-04 21:25 ` [PATCH] sched: Resolve sd_idle and first_idle_cpu Catch-22 - v1 Venkatesh Pallipadi
2011-02-07 13:50 ` Peter Zijlstra
2011-02-07 18:21 ` Venkatesh Pallipadi
2011-02-07 19:53 ` Suresh Siddha
2011-02-08 17:37 ` Venkatesh Pallipadi
2011-02-08 18:13 ` Misc sd_idle related fixes Venkatesh Pallipadi
2011-02-09 9:29 ` Peter Zijlstra
2011-02-10 17:24 ` Venkatesh Pallipadi
2011-02-08 18:13 ` [PATCH 1/3] sched: Resolve sd_idle and first_idle_cpu Catch-22 Venkatesh Pallipadi
2011-02-08 18:13 ` [PATCH 2/3] sched: fix_up broken SMT load balance dilation Venkatesh Pallipadi
2011-02-08 18:13 ` [PATCH 3/3] sched: newidle balance set idle_timestamp only on successful pull Venkatesh Pallipadi
2011-02-09 3:37 ` Mike Galbraith [this message]
2011-02-09 15:55 ` [PATCH] sched: Resolve sd_idle and first_idle_cpu Catch-22 - v1 Peter Zijlstra
2011-02-12 1:20 ` Suresh Siddha
2011-02-14 22:38 ` [PATCH] sched: Wholesale removal of sd_idle logic Venkatesh Pallipadi
2011-02-15 17:01 ` Vaidyanathan Srinivasan
2011-02-15 18:26 ` Venkatesh Pallipadi
2011-02-16 8:53 ` Vaidyanathan Srinivasan
2011-02-16 11:43 ` Peter Zijlstra
2011-02-16 13:50 ` [tip:sched/core] " tip-bot for Venkatesh Pallipadi
2011-02-15 9:15 ` [PATCH] sched: Resolve sd_idle and first_idle_cpu Catch-22 - v1 Peter Zijlstra
2011-02-15 19:11 ` Suresh Siddha
2011-02-18 1:05 ` Alex,Shi
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