Messages in this thread | | | Date | Mon, 11 Feb 2008 16:45:12 -0500 | From | Bill Davidsen <> | Subject | Re: Scheduler(?) regression from 2.6.22 to 2.6.24 for short-lived threads |
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Olof Johansson wrote:
>> However, I fail to understand the goal of the reproducer. Granted it shows >> irregularities in the scheduler under such conditions, but what *real* >> workload would spend its time sequentially creating then immediately killing >> threads, never using more than 2 at a time ? >> >> If this could be turned into a DoS, I could understand, but here it looks >> a bit pointless :-/ > > It seems generally unfortunate that it takes longer for a new thread to > move over to the second cpu even when the first is busy with the original > thread. I can certainly see cases where this causes suboptimal overall > system behaviour. > I think the moving to another CPU gets really dependent on the CPU type. On a P4+HT the caches are shared, and moving costs almost nothing for cache hits, while on CPUs which have other cache layouts the migration cost is higher. Obviously multi-core should be cheaper than multi-socket, by avoiding using the system memory bus, but it still can get ugly.
I have an IPC test around which showed that, it ran like hell on HT, and progressively worse as cache because less shared. I wonder why the latest git works so much better?
-- Bill Davidsen <davidsen@tmr.com> "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot
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