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Re: revivesa status 2008/07/09
On Jul 12, 2008, at 10:07 AM, Gary Thorpe wrote:
The advantages of SA are supposed to be on *I/O* bound workloads
because it can reduce overhead due to kernel context switches by
doing userland switches where appropriate (according to previous
benchmarks, research etc.), but I could be wron on this.
No. I/O bound switching in SA requires a kernel context switch
(because the thread blocks in the kernel).
SA is a win only when you have MANY threads blocking on user-space
synchronization primitives, and in that case, the benefit is
diminished greatly when you have threads being time-sliced against
each other because the timer firing involves the kernel (our
libpthread time-sliced by default).
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