From: Ingo Molnar <mingo@elte.hu>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
David Miller <davem@davemloft.net>,
linux-next@vger.kernel.org, linux-kernel@vger.kernel.org,
x86@kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [bloat] Measuring header file bloat effects on kernel build performance: a more than 2x slowdown ...
Date: Mon, 23 May 2011 12:55:22 +0200 [thread overview]
Message-ID: <20110523105522.GC24674@elte.hu> (raw)
In-Reply-To: <BANLkTi=Vbr+DRBy6sa7omGpvAb0uGunYMA@mail.gmail.com>
* Alexey Dobriyan <adobriyan@gmail.com> wrote:
> On Mon, May 23, 2011 at 12:09 PM, Ingo Molnar <mingo@elte.hu> wrote:
> > 24594a2bfcaa: [PATCH] x86-64 merge
> >
> > - Remove some unneeded prefetches. Just two are enough to kickstart
> > the hardware prefetcher.
> >
> > But despite touching prefetches explicitly, this too sloppily left the (now
> > dangling) prefetch.h include file around.
>
> Well, developer removes include, developer risks compile breakage.
If developer removes the final prefetch() from an unrelated header he might as
well think of removing the prefetch.h header. If there's compile breakage we
want to fix the breakage.
But yes, this is easily forgotten and the basic psychology is for header file
dependencies to grow, almost never to shrink.
To counteract that in a really good way we need tooling help - we are fighting
entropy here ...
> > Anway, what i tried to demonstrate with this mail how much *real* slowdown
> > in the kernel build our current header file bloat is causing. We could
> > literally halve our kernel build times if we fixed this!
>
> News at 11!
I have not seen *actual hard numbers* measured before, so how exactly is this
news at 11? So i think your condescending reply is neither fair nor justified.
Yes, we all knew that there's build time costs of header bloat - but it was
never AFAIK measured and posted to lkml in such a clear way.
Thanks,
Ingo
next prev parent reply other threads:[~2011-05-23 10:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-20 6:12 linux-next: build failure after merge of the final tree Stephen Rothwell
2011-05-20 15:24 ` Linus Torvalds
2011-05-20 16:16 ` Thomas Gleixner
2011-05-20 16:29 ` Linus Torvalds
2011-05-23 9:09 ` [bloat] Measuring header file bloat effects on kernel build performance: a more than 2x slowdown Ingo Molnar
2011-05-23 10:21 ` Alexey Dobriyan
2011-05-23 10:55 ` Ingo Molnar [this message]
2011-05-23 11:13 ` Alexey Dobriyan
2011-05-23 11:51 ` Ingo Molnar
2011-05-23 16:01 ` Linus Torvalds
2011-05-23 17:01 ` Ingo Molnar
2011-05-23 16:19 ` Sam Ravnborg
2011-05-28 0:36 ` Paul Gortmaker
2011-05-28 14:40 ` [PATCH] Fixes to the module.h splitup tree Ingo Molnar
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