Thread (21 messages) 21 messages, 10 authors, 2009-01-31

Re: [PATCH] percpu: add optimized generic percpu accessors

From: Tejun Heo <tj@kernel.org>
Date: 2009-01-31 06:12:21
Also in: lkml

Possibly related (same subject, not in this thread)

Hello, Rusty.

Rusty Russell wrote:
quoted
Rusty Russell wrote:
quoted
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.
quoted
quoted
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...
quoted
quoted
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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