Re: [PATCH v2 3/6] treewide: Replace memcpy(..., current->comm) with strscpy()

Em 27/05/2026 06:18, David Laight escreveu:
> On Tue, 26 May 2026 19:06:25 -0400
> Steven Rostedt <[email protected]> wrote:
> 
>> On Sun, 24 May 2026 19:38:53 -0300
>> André Almeida <[email protected]> wrote:
>>
>>> In order to increase the size of current->comm[] and to avoid breaking any
>>> existing code, replace memcpy() with strscpy(). The later function makes
>>> sure that the copy is NUL terminated. This is crucial given that the
>>> source buffer might be larger than the destination buffer and could
>>> truncate the NUL character out of it.
> ...
>> As tracing now slows it down by 3.9% which is a significant increase from 2.7%
>>
>> I really rather keep memcpy() here.

Thanks Steve for taking the time for benchmarking this!

> 
> I suspect the copies could/should be replaced by a copy_task_comm()
> function that can perform optimisations that strscpy[_pad]() can't
> do because it can (for example) assume that the source is terminated.
> 
> When the src and dst are the same size it can also degenerate to
> memcpy() - which should get inlined.
> The cost of copying 64 bytes might still be rather more than copying
> just 16.
> A compromise of 32 may be better.
> 
Ok, I will work on something like this for the v3.