linux-kernel - Re: [PATCH] x86/signal: Deinline get

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Message-ID: <20150928202401.GB4035@linux-uzut.site>
Date:	Mon, 28 Sep 2015 13:24:01 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Brian Gerst <brgerst@...il.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/signal: Deinline get_sigframe, save 240 bytes

On Mon, 28 Sep 2015, Denys Vlasenko wrote:

>On 09/28/2015 02:33 PM, H. Peter Anvin wrote:
>> This one makes me slightly nervous, because it isn't clear
>> that these aren't potentially performance sensitive.
>
>CALL instruction is not a crime :)
>It costs about the same as one read-modify-write
>operation on a memory operand.
>
>This function is used in signal delivery code.
>If performance critical code uses massive numbers
>of signals, it already has a problem, Unix signals
>are too inefficient. That's why we have futexes etc...

True, but in general I don't think that justifies anything -- and not only
referring to this particular signal patch.

Nothing really against or in favor of these patches, but I don't think that
saving 240 bytes (or whatever) is worth such changes, in fact we have Josh's
tinyfication project for those systems that do in fact care.

Thanks,
Davidlohr
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