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

[David Laight]

On Tue, 26 May 2026 19:06:25 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> On Sun, 24 May 2026 19:38:53 -0300
> André Almeida <andrealmeid@xxxxxxxxxx> 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.

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.

-- David

> 
> -- Steve