On Thu, Mar 06, 2008 at 10:20:45AM +0100, Roman Divacky wrote: >On Thu, Mar 06, 2008 at 12:22:17AM +0000, Jung-uk Kim wrote: >> Prefer clock_gettime(2) over gettimeofday(2) and use CLOCK_MONOTONIC_FAST. >> It is only used to track elapsed time and it does not have to be precise. > >what is the rationale behind this? what is the expected improvement? I am >not questioning the change I am just curious..
There's been a recent extensive thread about poor X11 performance and it turns out the the Xserver can issue multiple gettimeofday(2) calls every time it sees a mouse movement. gettimeofday(2) on FreeBSD is relatively expensive (the Project chose accuracy over speed) and clock_gettime(2) using CLOCK_MONOTONIC_FAST is a much cheaper alternative when accuracy isn't critical. The Xserver should be using clock_gettime(2) but there's a bug in its POSIX-compatibility selection. Applying a similar fix to moused is a logical extension. -- Peter Jeremy Please excuse any delays as the result of my ISP's inability to implement an MTA that is either RFC2821-compliant or matches their claimed behaviour.
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