[linux-lvm] Re: [PATCH] bdi_congestion_funp (was: Re: [PATCH] per process request limits (was Re: IO scheduler, queue depth, nr_requests))

[Andrew Morton]

Miquel van Smoorenburg <miquels at cistron.net> wrote:
>
> The pdflush-is-running-on-this-queue bit can probably remain as-is. It's
>  mostly meant to prevent 2 pdflush daemons from running the same queue.
>  I don't see much harm in pdflush #1 running on /dev/md0 which consists
>  of /dev/sda1 and /dev/sdb1 and pdflush #2 running on /dev/sdb2, right ?

Yes, having two pdflushes working the same spindle is a bit pointless but
is presumably fairly harmless.

The most important thing here is to prevent pdflush from blocking on
request exhaustion.  Because while pdflush sleeps on a particular disk, all
the others remain unserviced.