Messages in this thread |  | | Date | Fri, 2 May 2008 17:19:38 -0700 | From | Andrew Morton <> | Subject | Re: [RFC][-mm] Simple stats for cpu resource controller v3 |
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On Sat, 3 May 2008 05:26:46 +0530 Balaji Rao <balajirrao@gmail.com> wrote:
> > yes, that would be good. > OK, so when does account_system_time get called for the first time ? after > IRQs are set up, is it ? So, where do we place the hook ?
Don't know - I'd need to dive in and work that out, and it's probably better than you do this..
> Here's the patch. > > diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h > index 9007ccd..8a1b756 100644 > --- a/include/linux/percpu_counter.h > +++ b/include/linux/percpu_counter.h > @@ -21,7 +21,7 @@ struct percpu_counter { > #ifdef CONFIG_HOTPLUG_CPU > struct list_head list; /* All percpu_counters are on a list */ > #endif > - s32 *counters; > + s32 counters[NR_CPUS]; > };
Please, no. That's a 4092-byte increase in sizeof(struct percpu_counter). Hence a 12 kbyte increase in sizeof(struct ext3_sb_info). Let's just sort out the cgroup startup ordering.
<looks at __percpu_alloc_mask> <wanders off-topic>
Eric, is that optimal? alloc_percpu() will pass down cpu_possible_map in `mask', and we only need to allocate enough slots to cover the highest-set-bit in cpu_possible_map. However the implementation ignores `mask' and does
size_t sz = roundup(nr_cpu_ids * sizeof(void *), cache_line_size()); void *pdata = kzalloc(sz, gfp);
Now, if the highest-set-bit in cpu_possible_map is always equal to (1<<nr_cpu_ids) then it doesn't matter. But is that the case?
(If someone calls __percpu_alloc_mask with something that has less bits set than cpu_possible_map then it surely is wasteful, but that sounds unlikely).
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