From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Nikhil Rao <ncrao@google.com>, Paul Turner <pjt@google.com>,
Mike Galbraith <efault@gmx.de>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 00/18] Increase resolution of load weights
Date: Thu, 21 Apr 2011 18:32:37 +0200 [thread overview]
Message-ID: <1303403557.2035.148.camel@laptop> (raw)
In-Reply-To: <20110421061643.GA31388@elte.hu>
On Thu, 2011-04-21 at 08:16 +0200, Ingo Molnar wrote:
> * Nikhil Rao <ncrao@google.com> wrote:
>
> > Major TODOs:
> > - Detect overflow in update shares calculations (time * load), and set load_avg
> > to maximum possible value (~0ULL).
> > - tg->task_weight uses an atomic which needs to be updates to 64-bit on 32-bit
> > machines. Might need to add a lock to protect this instead of atomic ops.
> > - Check wake-affine math and effective load calculations for overflows.
> > - Needs more testing and need to ensure fairness/balancing is not broken.
>
> Please measure micro-costs accurately as well, via perf stat --repeat 10 or so.
>
> For example, on a testsystem doing 200k pipe triggered context switches (100k
> pipe ping-pongs) costs this much:
>
> $ taskset 1 perf stat --repeat 10 ./pipe-test-100k
>
> We want to know the delta in the 'instructions' value resulting from the patch
> (this can be measured very accurately) and we also want to see the 'cycles'
> effect - both can be measured pretty accurately.
>
> I've attached the testcase - you might need to increase the --repeat value so
> that noise drops below the level of the effect from these patches. (the effect
> is likely in the 0.01% range)
>
> It would also be nice to see how 'size vmlinux' changes with these patches
> applied, on a 'make defconfig' build.
Well, it shouldn't change at all for 64bit kernels (would be good to
double check), however 32bit kernels will get bigger and slower.
The problem is, the only alternative is to make 32bit !cgroup kernels
different, but then we end up with a massive wrappery mess... and the
last thing the load-balance code needs is more obfuscation.
next prev parent reply other threads:[~2011-04-21 16:29 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-20 20:51 [RFC][PATCH 00/18] Increase resolution of load weights Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 01/18] sched: introduce SCHED_POWER_SCALE to scale cpu_power calculations Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 02/18] sched: increase SCHED_LOAD_SCALE resolution Nikhil Rao
2011-04-28 9:54 ` Nikunj A. Dadhania
2011-04-28 17:11 ` Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 03/18] sched: use u64 for load_weight fields Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 04/18] sched: update cpu_load to be u64 Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 05/18] sched: update this_cpu_load() to return u64 value Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 06/18] sched: update source_load(), target_load() and weighted_cpuload() to use u64 Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 07/18] sched: update find_idlest_cpu() to use u64 for load Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 08/18] sched: update find_idlest_group() to use u64 Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 09/18] sched: update division in cpu_avg_load_per_task to use div_u64 Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 10/18] sched: update wake_affine path to use u64, s64 for weights Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 11/18] sched: update update_sg_lb_stats() to use u64 Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 12/18] sched: Update update_sd_lb_stats() " Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 13/18] sched: update f_b_g() to use u64 for weights Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 14/18] sched: change type of imbalance to be u64 Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 15/18] sched: update h_load to use u64 Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 16/18] sched: update move_task() and helper functions to use u64 for weights Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 17/18] sched: update f_b_q() to use u64 for weighted cpuload Nikhil Rao
2011-04-20 20:51 ` [RFC][Patch 18/18] sched: update shares distribution to use u64 Nikhil Rao
2011-04-21 6:16 ` [RFC][PATCH 00/18] Increase resolution of load weights Ingo Molnar
2011-04-21 16:32 ` Peter Zijlstra [this message]
2011-04-26 16:11 ` Nikhil Rao
2011-04-21 16:40 ` Peter Zijlstra
2011-04-28 7:07 ` Nikunj A. Dadhania
2011-04-28 11:48 ` Nikunj A. Dadhania
2011-04-28 12:12 ` Srivatsa Vaddagiri
2011-04-28 18:33 ` Nikhil Rao
2011-04-28 18:51 ` Paul Turner
2011-04-28 18:53 ` Paul Turner
2011-04-28 21:27 ` Nikhil Rao
2011-04-29 16:55 ` Paul Turner
2011-04-28 18:20 ` Nikhil Rao
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