Re: [ext3][kernels >= 2.6.20.7 at least] KDE going comatose when FS is under heavy write load (massive starvation)

Mikulas Patocka
2007-04-28T17:11:40Z

> So perhaps if there's any privileged reads going on then we should limit
> writes to a depth of 2 at most, with some timeout mechanism that would

SCSI has a "high priority" bit in the command block, so you can just set
it --- but I am not sure how well do disks support it.

Mikulas

> gradually allow the deepening of the hardware queue, as long as no
> highprio reads come inbetween? With 2 pending requests and even assuming
> worst-case seeks the user-visible latency would be on the order of 20-30
> msecs, which is at the edge of human perception. The problem comes when
> a hardware queue of 32-64 entries starves that one highprio read which
> then results in a 2+ seconds latency.
>
> Ingo
>