[PATCH] um: clean up mm creation

[Anton Ivanov]

On 22/09/2023 21:12, Johannes Berg wrote:
> On Fri, 2023-09-22 at 21:08 +0100, Anton Ivanov wrote:
>> On 22/09/2023 20:41, Johannes Berg wrote:
>>> On Fri, 2023-09-22 at 14:41 +0100, Anton Ivanov wrote:
>>>>
>>>> It is nearly twice slower than the current approach on a find /usr -type f -exec cat {} > /dev/null \;
>>>>
>>>
>>> Btw, I cannot reproduce that at all - seems about the same in my tests?
>>>
>>> Is there anything special in your setup?
>>>
>>> Or maybe it's because I'm using hostfs? But not sure why that would
>>> matter.
>>
>> I am using a ubd with ext4 sitting on an nfs server. The host, however,
>> has more than enough memory to cache all of it, so it is pretty much
>> like reading off a ramdisk as it is fully cached.
>>
>> It is quite clear in that case.
>>
> 
> Did you have your preempt patch applied also, btw? Because I was working
> off that now.
> 
> But even with PREEMPT turned off, I see basically no difference in such

One more thing. Is your find "real" /bin/find or busybox.

Real find will exec() /bin/cat
Busybox find will shortcut internally to the code of its cat applet. As 
a result it is much faster and there is no exec overhead.

> a benchmark. I was running only over /usr/bin/ because otherwise it's
> just too much time on my system overall, but there's basically no
> difference in the 4x4 matrix of
> 
>   - preempt off / preempt voluntary
>   - with / without my patch
> 
> johannes
> 

-- 
Anton R. Ivanov
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