Re: [PATCH] mm: page_alloc: Avoid marking zones full prematurelyafter zone_reclaim()

[Ric Mason]

Hi Michal,
On 04/09/2013 06:14 PM, Michal Hocko wrote:
> On Tue 09-04-13 18:05:30, Simon Jeons wrote:
> [...]
> > > I try this in v3.9-rc5:
> > > dd if=/dev/sda of=/dev/null bs=1MB
> > > 14813+0 records in
> > > 14812+0 records out
> > > 14812000000 bytes (15 GB) copied, 105.988 s, 140 MB/s
> > >
> > > free -m -s 1
> > >
> > >                    total       used       free     shared buffers
> > > cached
> > > Mem:          7912       1181       6731          0 663        239
> > > -/+ buffers/cache:        277       7634
> > > Swap:         8011          0       8011
> > >
> > > It seems that almost 15GB copied before I stop dd, but the used
> > > pages which I monitor during dd always around 1200MB. Weird, why?
> > Sorry for waste your time, but the test result is weird, is it?
> I am not sure which values you have been watching but you have to
> realize that you are reading a _partition_ not a file and those pages
> go into buffers rather than the page chache.

Interesting. ;-)

What's the difference between buffers and page cache? Why buffers don't 
grow?


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