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ib_srpt: Document impact of interrupt assignment on fairness

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git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@4447 d57e44dd-8a1f-0410-8b47-8ef2f437770f
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Bart Van Assche
2012-08-04 14:36:27 +00:00
parent 36a77c3708
commit 123911a2c3
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@@ -327,6 +327,15 @@ storage devices though (SSDs), DEVICE.threads_num should be set to 1 or 2 in
/etc/scst.conf in order to reach optimal performance for small block sizes
(e.g. 4 KB).
When multiple InfiniBand HCA's are present in a target system the Linux
kernel by default will assign the associated interrupt handlers to CPU 0.
Even irqbalance will often assign the interrupt handlers of multiple HCA's
to the same CPU. That is unfortunate because it leads to unfair handling of
SRP sessions. The solution is to assign InfiniBand HCA interrupts manually
to different CPU's. That's possible by writing looking up the InfiniBand
interrupt numbers in /proc/interrupts and by writing proper bitmasks into
/proc/irq/<n>/smp_affinity.
Performance Notes - Initiator Side
----------------------------------