Hello Parag and George, Thanks for immediate reply. The main problem is I am working on a SMP system. I have written a small program that just calls the gettimeofday(), one billion times. I have run it with time utility and it takes almost double time on SMP then a UP.
with kernel 2.6.10 on UP real 4m5.495s user 1m17.088s sys 2m48.046s With Kernel 2.6.10 on SMP real 6m24.485s user 1m43.723s sys 4m30.749s And the fact is this SMP machine is faster and with more memory than the UP one. In SMP systems it make a spinlock every time it got called, synchronizes both the processors, and unlock them. Thats all I know about it. George I am just working on your suggestion, let me know if it will work for SMPs. If there is some good implementation for SMP, please let me know. Thanks, - Puneet On Tue, 2005-02-22 at 08:36, George Anzinger wrote: > Parag Warudkar wrote: > > On Sunday 20 February 2005 05:58 am, [EMAIL PROTECTED] wrote: > > > >>985913 8.6083 vmlinux mark_offset_tsc > >>584473 5.1032 libc-2.3.2.so getc > > > > > > What makes you think mark_offset_tsc is slow? Do you have any comparative > > numbers? It might just be that the workload you are throwing at it > > justifies > > it. (For e.g. if your workload does a zillion system calls, system_call > > will > > show up as a hot spot in oprofile - doesn't necessarily mean it is slow - > > it's just overused.) Can you post the relevant code? > > He really is right. Mark offset is reading the PIT counter and that is not > only > rather dumb but dog slow. > > A suggestion, try the high res timers patch. Even if you don't use the > timers > the mark offset there is MUCH faster. It does not read the PIT. > > The difference is where we assume the jiffie bump is in time. If we assume > it > is at the point that the PIT interrupts, well then the only way to get to > that > is to read the PIT. If, on the other hand, we assume it is at the time after > the interrrupt where we mark offset, we can observe the "best" time for this > event based on the TSC and avoid reading the PIT. > > Try the HRT patch (see signature below) and see if if doesn't do better. > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
