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authorLinus Torvalds <torvalds@linux-foundation.org>2008-06-22 23:23:15 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-06-22 23:23:15 +0400
commit55d8538498f62ec72b5ba67aa386c7726f630475 (patch)
tree15ebcc7a51fdf1ff2bf76ade337a637c0990055d /include/linux/tty_driver.h
parent481c5346d0981940ee63037eb53e4e37b0735c10 (diff)
downloadlinux-55d8538498f62ec72b5ba67aa386c7726f630475.tar.xz
Fix performance regression on lmbench select benchmark
Christian Borntraeger reported that reinstating cond_resched() with CONFIG_PREEMPT caused a performance regression on lmbench: For example select file 500: 23 microseconds 32 microseconds and that's really because we totally unnecessarily do the cond_resched() in the innermost loop of select(), which is just silly. This moves it out from the innermost loop (which only ever loops ove the bits in a single "unsigned long" anyway), which makes the performance regression go away. Reported-and-tested-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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