Re: [PATCH 0/8] idle page tracking / working set estimation

Balbir Singh
2011-09-27T10:03:15Z

On Sat, Sep 17, 2011 at 9:09 AM, Michel Lespinasse <walken@google.com> wrote:
> Please comment on the following patches (which are against the v3.0 kernel).
> We are using these to collect memory utilization statistics for each cgroup
> accross many machines, and optimize job placement accordingly.
>
> The statistics are intended to be compared accross many machines - we
> don't just want to know which cgroup to reclaim from on an individual
> machine, we also need to know which machine is best to target a job onto
> within a large cluster. Also, we try to have a low impact on the normal
> MM algorithms - we think they already do a fine job balancing resources
> on individual machines, so we are not trying to mess up with that here.
>
> Patch 1 introduces no functionality; it modifies the page_referenced API
> so that it can be more easily extended in patch 3.
>
> Patch 2 documents the proposed features, and adds a configuration option
> for these. When the features are compiled in, they are still disabled
> until the administrator sets up the desired scanning interval; however
> the configuration option seems necessary as the features make use of
> 3 extra page flags - there is plenty of space for these in 64-bit builds,
> but less so in 32-bit builds...
>
> Patch 3 introduces page_referenced_kstaled(), which is similar to
> page_referenced() but is used for idle page tracking rather than
> for memory reclaimation. Since both functions clear the pte_young bits
> and we don't want them to interfere with each other, two new page flags
> are introduced that track when young pte references have been cleared by
> each of the page_referenced variants.

Sorry, I have trouble parsing this sentence, could you elaborate on "when"?

Balbir Singh