Re: slow performance on disk/network i/o full speed after drop_caches

Stefan Priebe - Profihost AG
2011-08-31T07:11:10Z

Hi Fengguang,
Hi Yanhai,

> you're abssolutely corect zone_reclaim_mode is on - but why?
> There must be some linux software which switches it on.
>
> ~# grep 'zone_reclaim_mode' /etc/sysctl.* -r -i
> ~#
>
> also
> ~# grep 'zone_reclaim_mode' /etc/sysctl.* -r -i
> ~#
>
> tells us nothing.
>
> I've then read this:
>
> "zone_reclaim_mode is set during bootup to 1 if it is determined that
> pages from remote zones will cause a measurable performance reduction.
> The page allocator will then reclaim easily reusable pages (those page
> cache pages that are currently not used) before allocating off node pages."
>
> Why does the kernel do that here in our case on these machines.

Can nobody help why the kernel in this case set it to 1?

Stefan