David Xu wrote: > On Wednesday 10 May 2006 02:23, Kris Kennaway wrote: > >>There are at least several issues here: >> >>...This may be general issues like >>gettimeofday() on Linux vs FreeBSD; clearly there is something *very >>big* to blame here. Mysql does do *lots* of such calls ... > > My last recall is that gettimeofday is not a syscall on Linux... I recall Matt talking about implementing gettimeofday() without a syscall. The basic idea is to have the kernel record some constants in a page that's mapped across all processes, then libc can just read the time from a known location. It might be nice to combine this with some of the other ideas being tossed around here: * On each clock tick, store a base time in a known location (page mapped read-only, no-execute across all memory maps) * libc can just read the base time (accurate to the clock rate) from a constant. Very, very fast. * For higher resolution, the kernel could record TSC and CPU clock speed data (per-CPU? Hmmm...) and libc could use that to fine-tune the time? Still some details I need to think through... TimReceived on Tue May 09 2006 - 22:31:42 UTC
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