BUFQ_PRIOCSCAN, IMHO, is superior to BUFQ_READPRIO.
AFAIK, it is not fully implemented, but even so it can significantly
improve interactive response time and even write throughput under
load.

For performance tuning, one can change the number of queues
(PRIOCSCAN_NQUEUE) as well as the integer constant priocscan_burst[].
The number of elements in the array corresponds to the number of
queues.  I use three (default) queues with priocscan_burst[512 128 32]
(this was approximately the peak of a roughly inverted-U-shaped
curve).  Both of these are
found in cscan_init() in kern/bufq_priocscan.c.



Regards,

--Blair


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