Re: Delete scheduler SD_WAKE_AFFINE and SD_WAKE_BALANCE flags
From: Nick Piggin
Date: Thu Jul 28 2005 - 20:27:05 EST
Chen, Kenneth W wrote:
Nick Piggin wrote on Thursday, July 28, 2005 4:35 PM
Wake balancing provides an opportunity to provide some input bias
into the load balancer.
For example, if you started 100 pairs of tasks which communicate
through a pipe. On a 2 CPU system without wake balancing, probably
half of the pairs will be on different CPUs. With wake balancing,
it should be much better.
Shouldn't the pipe code use synchronous wakeup?
Well pipes are just an example. It could be any type of communication.
What's more, even the synchronous wakeup uses the wake balancing path
(although that could be modified to only do wake balancing for synch
wakeups, I'd have to be convinced we should special case pipes and not
eg. semaphores or AF_UNIX sockets).
OK there are probably a number of things we can explore depending on
I hear you might be having problems with recent 2.6.13 kernels? If so,
it would be really good to have a look that before 2.6.13 goes out the
Yes I do :-(, apparently bumping up cache_hot_time won't give us the
performance boost we used to see.
what are the symptoms (eg. excessive idle time, bad cache performance).
Unfortunately it is kind of difficult to tune 2.6.13 on the basis of
2.6.12 results - although that's not to say it won't indicate a good
avenue to investigate.
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