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Date: Thu, 5 Sep 2013 10:15:39 +0530 From: Arun Sharma <asharma@...com> To: John Stultz <john.stultz@...aro.org> CC: LKML <linux-kernel@...r.kernel.org>, Andy Lutomirski <luto@...capital.net>, Kumar Sundararajan <kumar@...com>, Richard Cochran <richardcochran@...il.com>, "H. Peter Anvin" <hpa@...ux.intel.com> Subject: Re: clock_gettime_ns On 9/5/13 12:47 AM, John Stultz wrote: > If we're going to add a new interface that uses something other then a > timespec, we likely need to put some serious thought into that new > type, and see how it could be used across a number of syscalls. Some > of the discussion around dealing with the 2038 issue touched on this. [ I know you're not asking for perf data, but may be useful for new readers ] Here's the benchmarking I did in 2011: http://thread.gmane.org/gmane.linux.kernel/1233758/focus=1233781 Switching from timespec to s64 was worth 21%. My experience over the years is that this performance delta causes userspace guys to implement their own TSC based timers, against the advice from kernel developers. http://code.ohloh.net/search?s=wall%20now%20tsc%20hz&pp=0&fl=C&fl=C%2B%2B&ff=1&mp=1&ml=1&me=1&md=1&filterChecked=true I worry that trying to solve other clock problems will cause the kernel to continue to pass the time in memory instead of registers, giving the userspace TSC based implementations a reason to exist. -Arun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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