Xserver and Gettimeofday
Gabor Gombas
gombasg at sztaki.hu
Thu Aug 30 06:13:01 PDT 2007
On Wed, Aug 29, 2007 at 09:07:47PM -0700, Keith Packard wrote:
> It actually takes a timer signal every 20ms instead of calling
> gettimeofday for this purpose. Unfortunately, we also have many spin
> loops that wait for the hardware to finish some operation, and those
> generally want to timeout when the hardware locks up. Those call
> gettimeofday repeatedly, and while it looks bad on a profile, it's
> really just spinning through the kernel rather than sitting solely in
> user space spinning.
E.g. Linux on AMD64 implements time() and gettimeofday() completely in
user-space (the kernel exports the time in the VDSO page that is mapped
into the address space of every process), while clock_gettime() is a
real syscall.
Gabor
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MTA SZTAKI Computer and Automation Research Institute
Hungarian Academy of Sciences
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