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SubjectRe: [PATCH] shows Active/Inactive on per-node meminfo
Jesse Barnes <jbarnes@engr.sgi.com> wrote:
>
> On Friday, August 20, 2004 2:48 pm, Jesse Barnes wrote:
> > On Friday, August 20, 2004 2:02 pm, mita akinobu wrote:
> > > + for (i = 0; i < MAX_NR_ZONES; i++) {
> > > + *active += zones[i].nr_active;
> > > + *inactive += zones[i].nr_inactive;
> > > + *free += zones[i].free_pages;
> > > + }
> > > +}
> > > +
> > > - *free += zone->free_pages;
> > > + for_each_pgdat(pgdat) {
> > > + unsigned long l, m, n;
> > > + __get_zone_counts(&l, &m, &n, pgdat);
> > > + *active += l;
> > > + *inactive += m;
> > > + *free += n;
> > > }
> >
> > Just FYI, loops like this are going to be very slow on a large machine.
> > Iterating over every node in the system involves a TLB miss on every
> > iteration along with an offnode reference and possibly cacheline demotion.
>
> ...but I see that you're just adding the info to the per-node meminfo files,
> so it should be ok as long as people access a node's meminfo file from a
> local cpu. /proc/meminfo will still hurt a lot though.
>
> I bring this up because I ran into it once. I created a file
> called /proc/discontig which printed out detailed per-node memory stats, one
> node per line. On a large system it would literally take several seconds to
> cat the file due to the overhead of looking at all the pages and zone
> structures.
>

So was that an ack, a nack or a quack?

I'll queue the patch up so it doesn't get lost - could you please take a
closer look at the performance implications sometime, let me know?

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