Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH] percpu: add optimized generic percpu accessors | Date | Thu, 29 Jan 2009 12:36:46 +1030 |
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On Wednesday 28 January 2009 21:26:34 Tejun Heo wrote: > Hello,
Hi Tejun,
> 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 ).
Of course, if you want to be my hero, you could implement "soft" irq disable for all archs, which would make this cheaper.
> > 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.
Thanks, Rusty.
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