From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: holzheu@linux.vnet.ibm.com
Cc: Shailabh Nagar <nagar1234@in.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Venkatesh Pallipadi <venki@google.com>,
Suresh Siddha <suresh.b.siddha@intel.com>,
Ingo Molnar <mingo@elte.hu>, Oleg Nesterov <oleg@redhat.com>,
John stultz <johnstul@us.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Balbir Singh <balbir@linux.vnet.ibm.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Roland McGrath <roland@redhat.com>,
linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org
Subject: Re: [RFC][PATCH v2 1/7] taskstats: Add new taskstats command TASKSTATS_CMD_ATTR_PIDS
Date: Tue, 16 Nov 2010 13:36:12 +0100 [thread overview]
Message-ID: <1289910972.2109.598.camel@laptop> (raw)
In-Reply-To: <1289909779.1940.26.camel@holzheu-laptop>
On Tue, 2010-11-16 at 13:16 +0100, Michael Holzheu wrote:
> Ok, thanks. So sched_clock() seems to be a bad idea for our purposes.
>
> An alternative approach could be to have a global counter for the task
> snapshots, which is increased each time a snapshot is created for
> userspace. In addition to that we had to add a snapshot counter field to
> the task_struct that is set to the current value of the global counter
> each time a task leaves a CPU. Then userspace could ask for all tasks
> that have been active after snapshot number x. In the response userspace
> gets all tasks that have a snapshot number bigger than x together with
> the new snapshot number y that can be used for the next query.
>
> Still it would be useful to add a timestamp of the creation of the
> taskstats data in the response to userspace for calculating the interval
> time between two snapshots. Would the usage of ktime_get() be valid for
> that purpose?
ktime_get() can be insanely slow, but yes that's an option. Another
option is using local_clock() and living with the fact that it may be
out of sync (up to a jiffy or so) between CPUs.
The advantage of using ktime_get() as opposed to any other clock is that
userspace has access to it as well through:
clock_gettime(CLOCK_MONOTONIC), although that's arguably not too
relevant when all you're interested in is deltas.
next prev parent reply other threads:[~2010-11-16 12:36 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-11 17:03 [RFC][PATCH v2 0/7] taskstats: Enhancements for precise process accounting (version 2) Michael Holzheu
2010-11-11 17:03 ` [RFC][PATCH v2 1/7] taskstats: Add new taskstats command TASKSTATS_CMD_ATTR_PIDS Michael Holzheu
2010-11-13 19:20 ` Peter Zijlstra
2010-11-15 15:53 ` Michael Holzheu
2010-11-15 16:06 ` Peter Zijlstra
2010-11-15 17:09 ` Michael Holzheu
2010-11-15 17:21 ` Peter Zijlstra
2010-11-16 12:16 ` Michael Holzheu
2010-11-16 12:36 ` Peter Zijlstra [this message]
2010-11-13 19:39 ` Peter Zijlstra
2010-11-13 20:00 ` Balbir Singh
2010-11-15 14:50 ` Michael Holzheu
2010-11-11 17:03 ` [RFC][PATCH v2 2/7] taskstats: Add "/proc/taskstats" Michael Holzheu
2010-11-11 17:03 ` [RFC][PATCH v2 3/7] taskstats: Add thread group ID to taskstats structure Michael Holzheu
2010-11-11 17:03 ` [RFC][PATCH v2 4/7] taskstats: Add per task steal time accounting Michael Holzheu
2010-11-13 19:38 ` Peter Zijlstra
2010-11-15 14:50 ` Martin Schwidefsky
2010-11-15 15:11 ` Peter Zijlstra
2010-11-15 17:42 ` Martin Schwidefsky
2010-11-15 17:45 ` Peter Zijlstra
2010-11-15 17:47 ` Peter Zijlstra
2010-11-15 17:48 ` Peter Zijlstra
2010-11-15 17:50 ` Peter Zijlstra
2010-11-15 17:59 ` Martin Schwidefsky
2010-11-15 18:08 ` Peter Zijlstra
2010-11-16 8:51 ` Martin Schwidefsky
2010-11-16 12:16 ` Peter Zijlstra
2010-11-16 15:33 ` Martin Schwidefsky
2010-11-16 15:45 ` Peter Zijlstra
2010-11-16 16:05 ` Martin Schwidefsky
2010-11-16 18:39 ` Jeremy Fitzhardinge
2010-11-16 16:38 ` Avi Kivity
2010-11-16 16:43 ` Peter Zijlstra
2010-11-16 16:56 ` Avi Kivity
2010-11-16 17:06 ` Avi Kivity
2010-11-11 17:03 ` [RFC][PATCH v2 5/7] taskstats: Improve cumulative CPU " Michael Holzheu
2010-11-13 18:38 ` Oleg Nesterov
2010-11-15 15:55 ` Martin Schwidefsky
2010-11-15 16:03 ` Peter Zijlstra
2010-11-15 17:49 ` Martin Schwidefsky
2010-11-15 17:51 ` Peter Zijlstra
2010-11-15 18:00 ` Martin Schwidefsky
2010-11-15 18:10 ` Peter Zijlstra
2010-11-16 8:54 ` Martin Schwidefsky
2010-11-16 16:57 ` Michael Holzheu
2010-11-18 17:10 ` Oleg Nesterov
2010-11-19 19:46 ` Michael Holzheu
2010-11-16 17:34 ` Michael Holzheu
2010-11-16 17:50 ` Oleg Nesterov
2010-11-18 16:34 ` Oleg Nesterov
2010-11-11 17:03 ` [RFC][PATCH v2 6/7] taskstats: Fix accounting for non-leader thread exec Michael Holzheu
2010-11-11 17:11 ` [RFC][PATCH v2 7/7] taskstats: Precise process accounting user space Michael Holzheu
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