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SubjectRe: [PATCH] show per-process swap usage via procfs v3
On Thu, 12 Nov 2009 10:20:29 -0500 (EST)
Christoph Lameter <cl@linux-foundation.org> wrote:

> On Wed, 11 Nov 2009, KAMEZAWA Hiroyuki wrote:
>
> >
> > Index: mm-test-kernel/include/linux/mm_types.h
> > ===================================================================
> > --- mm-test-kernel.orig/include/linux/mm_types.h
> > +++ mm-test-kernel/include/linux/mm_types.h
> > @@ -228,6 +228,7 @@ struct mm_struct {
> > */
> > mm_counter_t _file_rss;
> > mm_counter_t _anon_rss;
> > + mm_counter_t _swap_usage;
>
> This is going to be another hit on vm performance if we get down this
> road.
>
> At least put
>
> #ifdef CONFIG_SWAP ?
>
> around this so that we can switch it off?
>
Hmm, okay. But I'm not sure I can do it in clean way.
(Or, I'll wait for you updates for mm_counters, or I do by myself.)

> > @@ -597,7 +600,9 @@ copy_one_pte(struct mm_struct *dst_mm, s
> > &src_mm->mmlist);
> > spin_unlock(&mmlist_lock);
> > }
> > - if (is_write_migration_entry(entry) &&
> > + if (!non_swap_entry(entry))
> > + rss[2]++;
> > + else if (is_write_migration_entry(entry) &&
> > is_cow_mapping(vm_flags)) {
> > /*
>
> What are the implications for fork performance?

This path is executed when page table entry contains a entry of
!pte_none() && !pte_present().

There are not very big chance to reach here.(this path is under unlikely()).

Thanks,
-Kame



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