Messages in this thread | | | Subject | RE: HT and idle = poll | Date | Thu, 6 Mar 2003 13:15:43 -0800 | From | "Nakajima, Jun" <> |
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Linus,
That's correct. Basically mwait is similar to hlt, but you can avoid IPI to wake up the processor waiting. A write to the address specified by monitor wakes up the processor, unlike hlt.
So our plan is to use monitor/mwait in the idle loop, for example, in the kernel to lower the latency.
Jun
> -----Original Message----- > From: Linus Torvalds [mailto:torvalds@transmeta.com] > Sent: Thursday, March 06, 2003 12:09 PM > To: Alan Cox > Cc: Linux Kernel Mailing List > Subject: Re: HT and idle = poll > > > On 6 Mar 2003, Alan Cox wrote: > > On Thu, 2003-03-06 at 19:30, Linus Torvalds wrote: > > > >So, don't use idle=poll with HT when you know your workload has idle > time! I > > > >have not tried oprofile, but it stands to reason that this would be a > > > > idle=poll probably needs to be doing "rep nop" in a tight loop. > > We already do that. It's not enough. The HT thing will still steal cycles > continually, since the "rep nop" is really only equivalent to a > "sched_yield()". > > Think of "rep nop" as yielding, and "mwait" as a true wait. > > (I don't actually have any real information on "mwait", so I may be wrong > about the details on the new instructions. They looked obvious enough, > though). > > Linus > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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