Messages in this thread | | | Date | Sat, 15 Sep 2012 21:44:54 +0200 | From | Borislav Petkov <> | Subject | Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets - bisected |
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On Sat, Sep 15, 2012 at 06:13:45PM +0200, Mike Galbraith wrote: > > Just for my n00b scheduler understanding: this way you're practically > > extending the timeslice of the task so that it gets done without being > > preempted and the lock-holding period of the preempted task gets smaller > > and thus you get more completed transactions in postgres during the > > benchmark run? > > Not really, preemption will happen, but when the preempting task goes to > sleep (or uses it's fair share), instead of selecting the leftmost task > (lowest vruntime), the preempted task gets the CPU back if we can do > that without violating fairness. If the preempted task happens to be a > userland spinlock holder, it then release the lock sooner, others don't > spin as long, do more work, less playing space heater while lock holder > waits for spinners to eat enough CPU to become less deserving that it.
Ok, I definitely grok this. Thanks for explaining.
-- Regards/Gruss, Boris.
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