Re: [PATCH]: VM 4/8 dont-rotate-active-list

[Andrew Morton <akpm@osdl.org>]

Nikita Danilov <nikita@clusterfs.com> wrote:
>
> Andrew Morton writes:
> 
> [...]
> 
>  > 
>  > I'll plop this into -mm to see what happens.  That should give us decent
>  > stability testing, but someone is going to have to do a ton of performance
>  > testing to justify an upstream merge, please.
> 
> I decided to drop this patch locally, actually. The version you merged
> doesn't behave as advertised: due to merge error l_active is not used in
> refill_inactive_zone() at all. As a result all mapped pages are simply
> parked behind scan page.
> 
> In my micro-benchmark workload (cyclical dirtying of mmaped file larger
> than physical memory) this obviously helps, because reclaim_mapped state
> is quickly reached and after that, mapped pages fall through to inactive
> list independently of their referenced bits. But such behavior is hard
> to justify in a general case.

Ah.

> Once I fixed the patch to take page_referenced() into account it stopped
> making any improvement in mmap micro-benchmark. But hey, if it is
> already in -mm let's test it, nobody understands how VM should work
> anyway. :-)

Sorry, I think I'll drop it in that case - making multiple changes at the
same time produces confusing results sometimes so let's minimise the number
of variables if there's an opportunity to do so.


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