linux-kernel - Re: [RFC[ Alloc in vsprintf

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Date:   Sun, 26 Jun 2022 13:13:18 -0700
From:   Joe Perches <joe@...ches.com>
To:     Kent Overstreet <kent.overstreet@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        David Laight <David.Laight@...LAB.COM>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Matthew Wilcox <willy@...radead.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC[ Alloc in vsprintf

On Sun, 2022-06-26 at 16:06 -0400, Kent Overstreet wrote:
> On Sun, Jun 26, 2022 at 12:53:26PM -0700, Joe Perches wrote:
> > In a reply to the printbufs thread, I wrote a proposal to use an
> > alloc to reduce stack in vsprintf when CONFIG_KALLSYMS is enabled.
> > 
> > No one has replied to this but I think it's somewhat sensible.
> > 
> > Thoughts?
> 
> As functions get converted to printbufs the separate stack allocated buffers
> become unnecessary, because printbufs have helpers that do bounds checking and
> make outputting to the vsprintf buffer painless. So it's not necessary - I
> haven't fully converted symbol_string() yet but I'll do so by the time I mail
> out the next round of patches.

_If_ the printfbufs patch series gets applied.
I think that series is not great yet.

Even if applied via something like the printbufs series, the
stack use of this function needs/could use attending.

~700 bytes of stack use here isn't great.