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SubjectRe: Avoid allocating during interleave from almost full nodes
A month ago, Christoph replied to pj:
>
> On Sat, 4 Nov 2006, Paul Jackson wrote:
>
> > Do you know of any existing counters that we could use like this?
> >
> > Adding a system wide count of pages allocated or scanned, just for
> > these fullnode hint caches, bothers me.
>
> There are already such counters. PGALLOC_* and PGSCAN_*. See
> include/linux/vmstat.h

These counters depend on CONFIG_VM_EVENT_COUNTERS.

The Kconfig comment for CONFIG_VM_EVENT_COUNTERS states:

VM event counters are only needed to for event counts to be
shown. They have no function for the kernel itself. This
option allows the disabling of the VM event counters.
/proc/vmstat will only show page counts.

(By the way - note the "needed to for event" phrasing error.)

The header file, include/linux/vmstat.h, for these counters states:

/*
* Light weight per cpu counter implementation.
*
* Counters should only be incremented and no critical kernel component
* should rely on the counter values.

Both these clearly state that I should not use these counters for real
kernel functions.

If that is so, I should find some other "time base" for the zonelist
caching.

If that is not so, then these comments need updating.

Anybody have any idea which is the case?

--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <pj@sgi.com> 1.925.600.0401
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