Messages in this thread | | | Subject | Re: [RFC 4/4]x86: avoid tlbstate lock if no enough cpus | From | Eric Dumazet <> | Date | Wed, 03 Nov 2010 08:25:23 +0100 |
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Le mercredi 03 novembre 2010 à 15:19 +0800, Shaohua Li a écrit : > On Wed, 2010-11-03 at 15:12 +0800, Eric Dumazet wrote: > > Le mercredi 03 novembre 2010 à 15:06 +0800, Shaohua Li a écrit : > > > just don't want to include the non-present cpus here. I wonder why we > > > haven't a variable to record online cpu number. > > > > What prevents a 256 cpus machine, to have 8 online cpus that all use the > > same TLB vector ? > > > > (Max 32 vectors, so 8 cpus share each vector, settled at boot time) > > > > Forget about 'online', and think 'possible' ;) > Hmm, the spread vectors to node already merged, how could the 8 cpus > share a vector? >
You boot a machine with 256 cpu.
They are online and very well.
Each vector is shared by at least 8 cpus, because 256/32 = 8. OK ?
Now you off-line 256-8 cpus, because you have HOTPLUG capability in your kernel and you have some policy to bring them up later if needed.
What happens ? Do you rebalance TLB vectors to make sure each cpu has its own vector ?
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