Messages in this thread | | | Date | Wed, 19 Dec 2007 23:04:33 -0800 (PST) | From | Christoph Lameter <> | Subject | Re: [patch 02/20] make the inode i_mmap_lock a reader/writer lock |
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> The only reason the x86 ticket locks have the 256 CPu limit is that > if they go any bigger, we can't use the partial registers so would > have to have a few more instructions.
x86_64 is going up to 4k or 16k cpus soon for our new hardware.
> A 32 bit spinlock would allow 64K cpus (ticket lock has 2 counters, > each would be 16 bits). And it would actually shrink the spinlock in > the case of preempt kernels too (because it would no longer have the > lockbreak field). > > And yes, I'll go out on a limb and say that 64k CPUs ought to be > enough for anyone ;)
I think those things need a timeframe applied to it. Thats likely going to be true for the next 3 years (optimistic assessment ;-)).
Could you go to 32bit spinlock by default?
How about NUMA awareness for the spinlocks? Larger backoff periods for off node lock contentions please.
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