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
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