On 11.04.2012 01:32, Luigi Rizzo wrote:
On Tue, Apr 10, 2012 at 07:05:00PM -0400, Barney Wolff wrote:
CPU cache?
Cx states?
powerd?
powerd is disabled, and i am going down to C1 at most
> sysctl -a | grep cx
hw.acpi.cpu.cx_lowest: C1
dev.cpu.0.cx_supported: C1/1 C2/80 C3/104
which shouldn't take so much. Sure, cache matters, but the
fact is, icmp processing on loopback should occur inline.
unless there is a forced descheduling on a select with timeout> 0
which would explain the extra few microseconds (and makes me worry
on how expensive is a scheduling decision...)
Things going through loopback go through a NETISR and may
end up queued to avoid LOR situations. In addition per-cpu
queues with hash-distribution for affinity may cause your
packet to be processed by a different core. Hence the additional
delay.
--
Andre
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