On 02/28/2013 03:40 PM, Michael Wang wrote: > Hi, Mike > > Thanks for your reply. > > On 02/28/2013 03:18 PM, Mike Galbraith wrote: >> On Thu, 2013-02-28 at 14:38 +0800, Michael Wang wrote: >> >>> + /* >>> + * current is the only task on rq and it is >>> + * going to sleep, current cpu will be a nice >>> + * candidate for p to run on. >>> + */ >> >> The sync hint only means it might be going to sleep soon, and even then, >> there can still be enough execution overlap to be a win to schedule >> cross core. Sched pipe numbers will always be much prettier if you do >> wakeup cpu affine, as it's ~100% scheduler and ~100% sync. > > Hmm.. so it's the comparison between 'cache benefit - execution overlap' > and 'latency - execution overlap'? > > I could not estimate how many latency will be added to wait for current > going to sleep (it should be faster than access cold data, isn't it?), > but I really like the cache benefit, unless sync doesn't means current > is going to sleep every time, but that's the promise of WF_SYNC, isn't it? > > You may lose >> a lot on other stuff if you interpret the hint as gospel truth. > > Could you please give more details on this point? > >> >> IMHO, sched pipe is a "how fat have I become" benchmark, not "how well >> do I perform". The scheduler performs well when it makes more work >> happen. Playing ping-pong with yourself is _exercise_, not a job :) > > That's right, may be I'm using the wrong description, it's the ops/sec > which has been doubled, that means 'fat', correct?
I mean could we say that more ops/sec means more works has been done? Regards, Michael Wang > > Regards, > Michael Wang > >> >> -Mike >> >> -- >> 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/ >> > -- 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/
