From: Peter Zijlstra <peterz@infradead.org>
To: viresh kumar <viresh.kumar@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Christoph Lameter <cl@linux.com>,
Linaro Kernel Mailman List <linaro-kernel@lists.linaro.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
vinmenon@codeaurora.org, shashim@codeaurora.org,
Michal Hocko <mhocko@suse.cz>, Mel Gorman <mgorman@suse.de>,
dave@stgolabs.net, Konstantin Khlebnikov <koct9i@gmail.com>,
Linux Memory Management List <linux-mm@kvack.org>,
Suresh Siddha <suresh.b.siddha@intel.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC] vmstat: Avoid waking up idle-cpu to service shepherd work
Date: Sun, 29 Mar 2015 12:24:40 +0200 [thread overview]
Message-ID: <20150329102440.GC32047@worktop.ger.corp.intel.com> (raw)
In-Reply-To: <20150328134457.GK27490@worktop.programming.kicks-ass.net>
On Sat, Mar 28, 2015 at 02:44:57PM +0100, Peter Zijlstra wrote:
> > Now there are few issues I see here (Sorry if they are all imaginary):
> > - In case a timer re-arms itself from its handler and is migrated from CPU A to B, what
> > happens if the re-armed timer fires before the first handler finishes ? i.e. timer->fn()
> > hasn't finished running on CPU A and it has fired again on CPU B. Wouldn't this expose
> > us to a lot of other problems? It wouldn't be serialized to itself anymore ?
>
> What I said above.
What I didn't say, but had thought of is that __run_timer() should skip
any timer that has RUNNING set -- for obvious reasons :-)
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WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: viresh kumar <viresh.kumar@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Christoph Lameter <cl@linux.com>,
Linaro Kernel Mailman List <linaro-kernel@lists.linaro.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
vinmenon@codeaurora.org, shashim@codeaurora.org,
Michal Hocko <mhocko@suse.cz>, Mel Gorman <mgorman@suse.de>,
dave@stgolabs.net, Konstantin Khlebnikov <koct9i@gmail.com>,
Linux Memory Management List <linux-mm@kvack.org>,
Suresh Siddha <suresh.b.siddha@intel.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC] vmstat: Avoid waking up idle-cpu to service shepherd work
Date: Sun, 29 Mar 2015 12:24:40 +0200 [thread overview]
Message-ID: <20150329102440.GC32047@worktop.ger.corp.intel.com> (raw)
In-Reply-To: <20150328134457.GK27490@worktop.programming.kicks-ass.net>
On Sat, Mar 28, 2015 at 02:44:57PM +0100, Peter Zijlstra wrote:
> > Now there are few issues I see here (Sorry if they are all imaginary):
> > - In case a timer re-arms itself from its handler and is migrated from CPU A to B, what
> > happens if the re-armed timer fires before the first handler finishes ? i.e. timer->fn()
> > hasn't finished running on CPU A and it has fired again on CPU B. Wouldn't this expose
> > us to a lot of other problems? It wouldn't be serialized to itself anymore ?
>
> What I said above.
What I didn't say, but had thought of is that __run_timer() should skip
any timer that has RUNNING set -- for obvious reasons :-)
next prev parent reply other threads:[~2015-03-29 10:24 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-26 5:39 [RFC] vmstat: Avoid waking up idle-cpu to service shepherd work Viresh Kumar
2015-03-26 5:39 ` Viresh Kumar
2015-03-26 20:18 ` Andrew Morton
2015-03-26 20:18 ` Andrew Morton
2015-03-27 4:49 ` Viresh Kumar
2015-03-27 4:49 ` Viresh Kumar
2015-03-27 9:16 ` Peter Zijlstra
2015-03-27 9:16 ` Peter Zijlstra
2015-03-27 9:30 ` Peter Zijlstra
2015-03-27 9:30 ` Peter Zijlstra
2015-03-27 11:11 ` Christoph Lameter
2015-03-27 11:11 ` Christoph Lameter
2015-03-27 12:02 ` Peter Zijlstra
2015-03-27 12:02 ` Peter Zijlstra
2015-03-27 19:45 ` Christoph Lameter
2015-03-27 19:45 ` Christoph Lameter
2015-03-28 4:28 ` Viresh Kumar
2015-03-28 4:28 ` Viresh Kumar
2015-03-28 11:41 ` Peter Zijlstra
2015-03-28 11:41 ` Peter Zijlstra
2015-03-28 4:18 ` Viresh Kumar
2015-03-28 4:18 ` Viresh Kumar
2015-03-28 9:53 ` Peter Zijlstra
2015-03-28 9:53 ` Peter Zijlstra
2015-03-28 11:57 ` viresh kumar
2015-03-28 11:57 ` viresh kumar
2015-03-28 12:04 ` Viresh Kumar
2015-03-28 12:04 ` Viresh Kumar
2015-03-28 13:44 ` Peter Zijlstra
2015-03-28 13:44 ` Peter Zijlstra
2015-03-29 10:24 ` Peter Zijlstra [this message]
2015-03-29 10:24 ` Peter Zijlstra
2015-03-30 12:02 ` Viresh Kumar
2015-03-30 12:02 ` Viresh Kumar
2015-03-30 12:47 ` Peter Zijlstra
2015-03-30 12:47 ` Peter Zijlstra
2015-03-30 13:14 ` Viresh Kumar
2015-03-30 13:14 ` Viresh Kumar
2015-03-30 13:59 ` Peter Zijlstra
2015-03-30 13:59 ` Peter Zijlstra
2015-03-30 16:17 ` Viresh Kumar
2015-03-30 16:17 ` Viresh Kumar
2015-03-30 16:25 ` Peter Zijlstra
2015-03-30 16:25 ` Peter Zijlstra
2015-03-29 12:01 ` Viresh Kumar
2015-03-29 12:01 ` Viresh Kumar
2015-03-29 17:24 ` Peter Zijlstra
2015-03-29 17:24 ` Peter Zijlstra
2015-03-30 15:08 ` Michal Hocko
2015-03-30 15:08 ` Michal Hocko
2015-03-30 15:14 ` Peter Zijlstra
2015-03-30 15:14 ` Peter Zijlstra
2015-03-30 15:42 ` Christoph Lameter
2015-03-30 15:42 ` Christoph Lameter
2015-03-27 14:19 ` Michal Hocko
2015-03-27 14:19 ` Michal Hocko
2015-03-28 4:34 ` Viresh Kumar
2015-03-28 4:34 ` Viresh Kumar
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