Re: [PATCH] syscall latency improvement #1

[Andrew Morton <akpm@zip.com.au>]

Linus Torvalds wrote:
> 
> It should be eminently testable. Just remove the cli from the standard
> kernel, and do before-and-after tests.
> 

#include <unistd.h>

main()
{
        int i = 100 * 1000 * 1000;

        while (i--)
                getpid();
}

With cli:
	./a.out  22.05s user 15.31s system 99% cpu 37.361 total

without cli: 
	./a.out  18.29s user 17.42s system 99% cpu 35.731 total


That's 4.6%.  Intel P3.

It's also 306 cycles per iteration.  So the cli added 14 cycles.

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