Re: [PATCH] mm: moving dirty pages balancing to pdfludh entirely

["Antonio Vargas" <windenntw@gmail.com>]

On 6/28/06, Nikita Danilov <nikita@clusterfs.com> wrote:
> Ananiev, Leonid I writes:
>  > >From Leonid Ananiev
>
> Hello,
>
>  >
>  > Moving dirty pages balancing from user to kernel thread pdfludh entirely
>  > reduces extra long write(2) latencies, increases performance.
>  >
>
> [...]
>
>  >      The benchmarks IOzone and Sysbench for file size 50% and 120% of
>  > RAM size on Pentium4, Xeon, Itanium have reported write and mix
>  > throughput increasing about 25%. The described Iozone > 0.1 sec write(2)
>
> Results are impressive.
>
> Wouldn't this interfere with current->backing_dev_info logic? This field
> is set by __generic_file_aio_write_nolock() and checked by
> may_write_to_queue() to force heavy writes to do more pageout. Maybe
> pdflush threads should set this field too?
>
>  > latencies are deleted. The condition writeback_in_progress() is tested
>  > earlier now. As a result extra pdflush works are not created and number
>  > of context switches increasing is inside variation limites.
>
> Nikita.

Maybe we should keep the sync-write logic if there is only one online
cpu, and thus avoiding extra context switches when they are not
profitable?

-- 
Greetz, Antonio Vargas aka winden of network