[PATCH] um: "borrow" cmpxchg from x86 tree in UML

[Anton Ivanov]

On 13/11/2020 15:58, Johannes Berg wrote:
> On Fri, 2020-11-13 at 13:48 +0000, Anton Ivanov wrote:
>>
>> I think that was it. Or to be more exact, I hope that was it.
>>
>> I went a few times through asm-generic and that looks like all the
>> bits which are worth implementing for a uniprocessor architecture as a
>> replacement for their generic equivalents.
> 
> It seems that word-at-a-time.h with CONFIG_DCACHE_WORD_ACCESS might
> be worthwhile as well?
> 
> Also perhaps bug.h; there are a lot of BUG_ON/WARN_ON and similar
> things, and especially the _ONCE part looks better there?
> 
> ftrace is probably not worth the effort ...
> 
> johannes
> 
> 
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There is one more which makes for a surprisingly big difference - a couple of more % on find /usr -type f -exec cat {} > /dev/null \;

bitops.h

Actually, it is not that surprising, fs and memory which are exercised this way have bitops all over the place.

Patch coming shortly.

I also have a patch to switch to proper cmpxchg in the futex/uaccess, but that has to go in after everything else. If atomics and cmpxchg have not gone in, it actually does more harm than good.

A.

-- 
Anton R. Ivanov
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