Hi,
Running kernel 2.2.10-rmk2-stk1, I have noticed that context switch
times are pretty terrible. Running lmbench to measure this reports the
following on my 200MHz SA-110:
Context switching - times in microseconds - smaller is better
-------------------------------------------------------------
Host OS 2p/0K 2p/16K 2p/64K 8p/16K 8p/64K 16p/16K 16p/64K
ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw
--------- ------------- ----- ------ ------ ------ ------ ------- -------
armv4l-li Linux 2.2.10- 200 410 914 453 931 434 930
armv4l-li Linux 2.2.10- 196 415 917 434 955 435 939
armv4l-li Linux 2.2.10- 199 410 915 455 955 434 948
armv4l-li Linux 2.2.10- 198 413 911 433 947 434 934
I know I've heard both good and bad things about lmbench, but are these
numbers fairly accurate? Looking at the context switch code in
proc-sa110.S shows comments pertaining to flushing the cache being
horribly slow, which I'm guessing is because to flush it you have to
read 16KB of data from the cache flush area.
Have there been many changes to the context switching code in 2.3 at
all that attempt to speed this up? Thanks.
--
Kyle Mestery | StorageTek's Storage Networking Group
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