Messages in this thread | | | Date | Fri, 16 Jan 2009 01:15:44 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] percpu: add optimized generic percpu accessors |
| |
* Herbert Xu <herbert@gondor.apana.org.au> wrote:
> Ingo Molnar <mingo@elte.hu> wrote: > > > >> Of course. But do any architectures actually _need_ that for a single > >> read? > > > > not for a read i guess - but for the other ops like add/and/or/xor. > > One of the things I'd like to see happen with this work is for us to > have a cheap per-cpu atomic counter that we can use for SNMP stats. > > If we can make the inc/add variants into a single instruction, then it > won't need to disable preemption or interrupts. > > So if you could design the API such that we have a variant of add/inc > that automatically disables/enables preemption then we can optimise that > away on x86.
Yeah. percpu_add(var, 1) does exactly that on x86.
Ingo
| |