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SubjectRe: [PATCH] mm: moving dirty pages balancing to pdfludh entirely
Ananiev, Leonid I writes:
> Nikita Danilov writes:
> > Exactly to the contrary: as I explained to you, if you have more
> devices
> > than pdflush threads
> I do not believe that Bret Towe has more devices than
> MAX_PDFLUSH_THREADS=8.

Some people do, should they suffer? :-)

>
> > See how wbc.nr_to_write is set up by balance_dirty_pages().
> It is number TO write but I said about number after what user has to
> write-out all dirty pages.

Not _all_, only nr_to_write of them:

if (pages_written >= write_chunk)
break; /* We've done our duty */

>
> > imagine that MAX_PDFLUSH_THREADS equals 1
> Imagine that CONFIG_NR_CPUS=1 for smp.
> Kernel has a lot of "big enough" constants.

Then why introduce more of them?

In current design each thread is responsible for write-out. This means
that write-out concurrency level scales together with the number of
writers. You propose to limit write-out concurrency by
MAX_PDFLUSH_THREADS. Obviously this is an artificial limit that will be
sub-optimal sometimes.

>
> Leonid

Nikita.
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