lkml.org 
[lkml]   [2023]   [Dec]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] tracing: Update snapshot buffer on resize if it is allocated
On Mon, 11 Dec 2023 12:51:52 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Mon, 11 Dec 2023 21:31:34 +0900
> Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
>
> > On Sun, 10 Dec 2023 22:54:47 -0500
> > Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > > From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> > >
> > > The snapshot buffer is to mimic the main buffer so that when a snapshot is
> > > needed, the snapshot and main buffer are swapped. When the snapshot buffer
> > > is allocated, it is set to the minimal size that the ring buffer may be at
> > > and still functional. When it is allocated it becomes the same size as the
> > > main ring buffer, and when the main ring buffer changes in size, it should
> > > do.
> >
> > nit: There seems two "when the snapshot buffer is allocated" case, maybe latter
> > "it" means main buffer?
>
> I changed the paragraph to be:
>
> The snapshot buffer is to mimic the main buffer so that when a snapshot is
> needed, the snapshot and main buffer are swapped. When the snapshot buffer
> is allocated, it is set to the minimal size that the ring buffer may be at
> and still functional. When it is allocated it becomes the same size as the
> main ring buffer, and when the main ring buffer changes in size, the
> snapshot should also change in size if it is allocated.

Yeah, this makes clearer.

>
> >
> > >
> > > Currently, the resize only updates the snapshot buffer if it's used by the
> > > current tracer (ie. the preemptirqsoff tracer). But it needs to be updated
> > > anytime it is allocated.
> > >
> > > When changing the size of the main buffer, instead of looking to see if
> > > the current tracer is utilizing the snapshot buffer, just check if it is
> > > allocated to know if it should be updated or not.
> > >
> > > Also fix typo in comment just above the code change.
> > >
> >
> > Looks good to me.
> >
> > Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> Thanks!
>
> >
> > BTW, the historical naming leads this kind of issues.
> > Maybe we'd better to rename 'max_buffer' to 'snapshot_buffer'?
>
> Agreed. But that's a cleanup for another day. Hmm, maybe that too should be
> marked as "KTODO"?

Yes!

>
> https://lore.kernel.org/all/369bc919-1a1d-4f37-9cc9-742a86a41282@kadam.mountain/
>

Ah, this is a good idea.

>
> There's a lot of things that we have been discussing on these ring-buffer
> patches that could be KTODO items.

Thanks,

>
> -- Steve


--
Masami Hiramatsu (Google) <mhiramat@kernel.org>

\
 
 \ /
  Last update: 2023-12-12 00:14    [W:0.044 / U:0.768 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site