From: Linus Torvalds <torvalds@linux-foundation.org>
To: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Nick Andrew <nick@nick-andrew.net>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@suse.de>,
netdev@vger.kernel.org, Bjorn Helgaas <bjorn.helgaas@hp.com>
Subject: Re: [PATCH] vsprintf.c: Reduce sizeof struct printf_spec from 24 to 8 bytes
Date: Sat, 6 Mar 2010 18:24:55 -0800 (PST) [thread overview]
Message-ID: <alpine.LFD.2.00.1003061818530.4033@localhost.localdomain> (raw)
In-Reply-To: <alpine.LFD.2.00.1003061755400.23804@localhost.localdomain>
On Sat, 6 Mar 2010, Linus Torvalds wrote:
> the 'pointer()' function has a 200+ byte stack footprint on x86-64. And
> vsnprintf itself is about 100+ bytes. So that stack depth is way bigger
> than I would have expected.
>
> I'm not sure _why_ that stack footprint for 'pointer()' is so big, but I
> bet it's due to some simple inlining, and gcc (once more) sucking at it
> and not being able to combine stack frames. It's a damn shame.
Yeah, a few noinline's gets 'pointer()' to just save registers on the
stack, no need for any extra buffers (which then is ok for your recursion
case - the other subfunctions it can call have their own buffers, of
course, but they won't be in the recursive call-path except at the leaf.
vsnprintf() itself seems less obviously fixable. I'm not sure wht gcc
decides it needs 88 bytes of temp-space there.
Linus
next prev parent reply other threads:[~2010-03-07 2:24 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1267682641.git.joe@perches.com>
2010-03-04 6:27 ` [PATCH 1/2] vsprintf: Recursive vsnprintf: Add "%pV", struct va_format Joe Perches
2010-03-04 6:27 ` [PATCH 2/2] device.h drivers/base/core.c Convert dev_<level> macros to functions Joe Perches
2010-03-04 22:38 ` [RESEND PATCH 0/2] Make functions of dev_<level> macros, recursive vsnprintf Andrew Morton
2010-03-04 23:06 ` Linus Torvalds
2010-03-06 21:36 ` Joe Perches
2010-03-06 22:03 ` Linus Torvalds
2010-03-06 22:30 ` Joe Perches
2010-03-06 22:52 ` Linus Torvalds
2010-03-06 22:57 ` Linus Torvalds
2010-03-06 23:35 ` Joe Perches
2010-03-06 23:46 ` Linus Torvalds
2010-03-06 23:48 ` Linus Torvalds
2010-03-06 23:57 ` Joe Perches
2010-03-06 23:58 ` Linus Torvalds
2010-03-07 1:10 ` [PATCH] vsprintf.c: Reduce sizeof struct printf_spec from 24 to 8 bytes Joe Perches
2010-03-07 2:03 ` Linus Torvalds
2010-03-07 2:24 ` Linus Torvalds [this message]
2010-03-07 2:33 ` [PATCH] vsprintf.c: Use noinline_for_stack Joe Perches
2010-03-08 23:39 ` Joe Perches
2010-03-13 0:25 ` Andrew Morton
2010-03-13 15:35 ` Linus Torvalds
2010-03-13 17:44 ` Joe Perches
2010-03-13 19:54 ` [PATCH] vsprintf.c: remove stack variable ksym from Joe Perches
2010-03-15 15:01 ` Paulo Marques
[not found] ` <f2b24d484347c083fa87856a75c1d96102af9005.1267682641.git.joe@perches.com>
2010-03-05 0:56 ` [PATCH 2/2] device.h drivers/base/core.c Convert dev_<level> macros to functions Andrew Morton
2010-03-05 1:00 ` Andrew Morton
2010-03-05 2:46 ` Joe Perches
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