Re: [PATCH 2/2] alloc_tag: skip pgalloc_tag_swap if profiling is disabled

[Andrew Morton]

On Thu, 26 Dec 2024 15:07:39 -0800 Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:

> On Thu, Dec 26, 2024 at 3:01 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Thu, 26 Dec 2024 13:16:39 -0800 Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
> >
> > > When memory allocation profiling is disabled, there is no need to swap
> > > allocation tags during migration. Skip it to avoid unnecessary overhead.
> > >
> > > Fixes: e0a955bf7f61 ("mm/codetag: add pgalloc_tag_copy()")
> > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> > > Cc: stable@xxxxxxxxxxxxxxx
> >
> > Are these changes worth backporting?  Some indication of how much
> > difference the patches make would help people understand why we're
> > proposing a backport.
> 
> The first patch ("alloc_tag: avoid current->alloc_tag manipulations
> when profiling is disabled") I think is worth backporting. It
> eliminates about half of the regression for slab allocations when
> profiling is disabled.

um, what regression?  The changelog makes no mention of this.  Please
send along a suitable Reported-by: and Closes: and a summary of the
benefits so that people can actually see what this patch does, and why.