From: Adrian Bunk <bunk@stusta•de>
To: Linus Torvalds <torvalds@linux-foundation•org>
Cc: Andrew Morton <akpm@linux-foundation•org>,
Alexey Dobriyan <adobriyan@gmail•com>,
linux-kernel@vger•kernel.org, netdev@vger•kernel.org
Subject: Re: 2.6.23-rc1: BUG_ON in kmap_atomic_prot()
Date: Thu, 26 Jul 2007 20:07:21 +0200 [thread overview]
Message-ID: <20070726180721.GN3572@stusta.de> (raw)
In-Reply-To: <alpine.LFD.0.999.0707241246130.3607@woody.linux-foundation.org>
On Tue, Jul 24, 2007 at 12:48:13PM -0700, Linus Torvalds wrote:
>
>
> On Tue, 24 Jul 2007, Adrian Bunk wrote:
> >
> > > But do we
> > > care so much that it's worth inlining something like buffered_rmqueue()?
> > >...
> >
> > Where is the problem with having buffered_rmqueue() inlined?
>
> In this case, it was a pain to just even try to find the call chain, or
> read the asm.
Optimization versus debugging is a common issue...
As I said, it might make sense to disable this optimization depending on
some debugging option.
> I would encourage lots of kernel hackers to read the assembler code gcc
> generates. I suspect people being aware of code generation issues (and
> writing their code with that in mind) is a *much* bigger performance
> impact than gcc inlining random functions.
>
> So maybe I'm old-fashioned and crazy, but "readability of the asm result"
> actually is a worthwhile goal. Not because we care directly, but because
> I'd like to encourage people to do it, due to the *indirect* benefits.
This would lead to people trying to optimize code for one gcc version -
and the code might stay this way for 10 years.
People should write readable C code. This also has the best chances of
resulting in good performance with the next gcc version on the next
generation hardware.
> Linus
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
next prev parent reply other threads:[~2007-07-26 18:07 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <alpine.LFD.0.999.0707221351030.3607@woody.linux-foundation.org>
[not found] ` <20070723183839.GA5874@martell.zuzino.mipt.ru>
[not found] ` <20070723190152.GA5755@martell.zuzino.mipt.ru>
2007-07-23 20:24 ` 2.6.23-rc1: BUG_ON in kmap_atomic_prot() Andrew Morton
2007-07-23 20:40 ` Alexey Dobriyan
2007-07-23 21:01 ` Alexey Dobriyan
2007-07-23 21:11 ` Andrew Morton
2007-07-23 21:28 ` Linus Torvalds
2007-07-23 21:37 ` Sam Ravnborg
2007-07-24 17:59 ` Adrian Bunk
2007-07-24 18:14 ` Linus Torvalds
2007-07-24 18:28 ` Andrew Morton
2007-07-24 19:15 ` Linus Torvalds
2007-07-24 19:40 ` Adrian Bunk
2007-07-24 19:48 ` Linus Torvalds
2007-07-26 18:07 ` Adrian Bunk [this message]
2007-07-26 18:19 ` Linus Torvalds
2007-07-24 20:27 ` Andi Kleen
2007-07-24 19:45 ` Linus Torvalds
2007-07-26 6:09 ` commit 7e92b4fc34 - x86, serial: convert legacy COM ports to platform devices - broke my serial console H. Peter Anvin
2007-07-23 22:04 ` 2.6.23-rc1: BUG_ON in kmap_atomic_prot() Alexey Dobriyan
2007-07-23 22:27 ` Andrew Morton
2007-07-24 5:20 ` Alexey Dobriyan
2007-07-24 8:17 ` Jens Axboe
2007-07-24 8:22 ` Jens Axboe
2007-07-24 8:34 ` Andrew Morton
2007-07-24 14:00 ` Dan Williams
2007-07-24 13:55 ` Dan Williams
2007-07-24 10:01 ` Mike Galbraith
2007-07-24 10:37 ` Mike Galbraith
2007-07-24 16:28 ` Andrew Morton
2007-07-24 18:25 ` Linus Torvalds
2007-07-24 20:05 ` Alexey Dobriyan
2007-07-25 5:09 ` Mike Galbraith
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