Re: [PATCH] shows Active/Inactive on per-node meminfo

[Jesse Barnes <jbarnes@engr.sgi.com>]

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.

Jesse