Re: [linux-audio-dev] Re: [PATCH really] latency improvements, one reschedule moved

[Roger Larsson <roger.larsson@norran.net>]

Zlatko Calusic wrote:
> 
> Roger Larsson <roger.larsson@norran.net> writes:
> 
> > Again... :-(
> >
> > Patch included this time...
> >
> 
> Hi, Roger, Linus, others!
> 
> 2.4.0-test3-pre4 (which includes this patch) is really a pleasant
> surprise. The I/O bandwidth has greatly improved and I'm still trying
> to understand how can patch this simple be so effective. :)
> 
> Great work Roger!
> 
> I see this as the first (and most critical) step of returning my faith
> in good performing 2.4.0-final.
> 
> Keep up the good work!
> --
> Zlatko

It was not intended to give better performance...
(something masks the expected latency improvements - floppy is
disturbing
 me, recal_interrupt. And kmem stuff - but that is more understandable
 we will issue additional 'kmem_cache_reap']


I examined the patches again and the fact that it runs
do_try_to_free_pages
periodically may improve performance due to its page cleaning effect -
all pages won't be dirty at the same time...

But it has a downside too - it will destroy the LRU order of pages...
PG_referenced loses some of its meaning...

Streaming writes are likely to gain the most.
Non uniform random accesses may loose :-(


I have an idea...

/RogerL

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