Messages in this thread | | | Date | Sat, 31 Jan 2009 15:11:14 +0900 | From | Tejun Heo <> | Subject | Re: [PATCH] percpu: add optimized generic percpu accessors |
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Hello, Rusty.
Rusty Russell wrote: >> Rusty Russell wrote: >>> If the stats are only manipulated in one context, than an atomic >>> requirement is overkill (and expensive on non-x86). >> Yes, it is. I was hoping it to be not more expensive on most archs. >> It isn't on x86 at the very least but I don't know much about other >> archs. > > Hmm, you can garner this from the local_t stats which were flying around. > (see Re: local_add_return from me), or look in the preamble to > http://ozlabs.org/~rusty/kernel/rr-latest/misc:test-local_t.patch ).
Ah... Great.
> Of course, if you want to be my hero, you could implement "soft" irq > disable for all archs, which would make this cheaper.
I suppose you mean deferred execution of interrupt handlers for quick atomicities. Yeah, that would be nice for things like this.
>>> Other than the shouting, I liked Christoph's system: >>> - CPU_INC = always safe (eg. local_irq_save/per_cpu(i)++/local_irq_restore) >>> - _CPU_INC = not safe against interrupts (eg. get_cpu/per_cpu(i)++/put_cpu) >>> - __CPU_INC = not safe against anything (eg. per_cpu(i)++) >>> >>> I prefer the name 'local' to the name 'cpu', but I'm not hugely fussed. >> I like local better too but no biggies one way or the other. > > Maybe kill local_t and take the name back. I'll leave it to you... > >>> Ah, I did not realize that you celebrated Australia day :) >> Hey, didn't know Australia was founded on lunar New Year's day. >> Nice. :-) > > That would have been cool, but no; first time in 76 years they matched tho.
It was a joke. :-)
Thanks.
-- tejun
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