Messages in this thread | | | Subject | Re: [PATCH 0/4] cputime: Virtual cputime accounting small cleanups and consolidation | From | Peter Zijlstra <> | Date | Thu, 21 Jun 2012 00:26:32 +0200 |
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On Tue, 2012-06-19 at 15:43 +0200, Frederic Weisbecker wrote: > > I wish we could do more vtime cputime accounting consolidation > but archs do the things pretty differently although I bet the > behaviour could be more unified. > Yes.. so s390,ia64 use thread_info, ppc uses their paca (arch private precursor to per-cpu data).
So I understand why s390,ia64 want the sched hook, but I don't see why ppc would need it, their account_process_tick() can fold whatever they need on the tick.
So I think reworking s390,ia64 to use per-cpu storage should get rid of this switch hook altogether.
Now everybody using VIRT_CPU_ACCOUNTING has the syscall/__irq_{enter,exit} hooks and uses 64bit cputime_t.
IRQ_TIME_ACCOUNTING only has the __irq_{enter,exit} hook and uses unsigned long cputime_t, it adds cputime_one_jiffy every tick when the per-cpu counter is ahead of the cputime.
We could merge both and do away with the 64bit cputime thing by keeping a (2nd) per-cpu kernel_cpustat which we fill with optional syscall/irq hooks and have account_process_tick() first check if any of the fine-grained fields overflow and if not, fall back to the regular tick accounting (much like an extended irqtime_account_process_tick).
This would merge the fine-grain and tick based code-paths and do away with the whole cputime_t mess, it would also merge the VIRT and IRQ paths and make Frederic's optional syscall accounting trivial.
Or am I missing something obvious here? -- its late after all.
I'll try and write some code tomorrow.
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