From: Denys Vlasenko <dvlasenk@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/signal: Deinline get_sigframe, save 240 bytes
Date: Mon, 28 Sep 2015 15:43:11 +0200 [thread overview]
Message-ID: <560943EF.4040407@redhat.com> (raw)
In-Reply-To: <099BA174-FB96-4849-BCD2-807D9A6B9580@zytor.com>
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...
> On September 28, 2015 5:23:57 AM PDT, Denys Vlasenko <dvlasenk@redhat.com> wrote:
>> This function compiles to 277 bytes of machine code and has 4
>> callsites.
I must correct myself: there are two callsites, not four.
(There are four calls in the source, but two of them are
in 32-bit code and two are in 64-bit).
next prev parent reply other threads:[~2015-09-28 13:43 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-28 12:23 [PATCH] x86/apic: Deinline __x2apic_disable, save 467 bytes Denys Vlasenko
2015-09-28 12:23 ` [PATCH] x86: Deinline e820_type_to_string, save 126 bytes Denys Vlasenko
2015-09-30 19:57 ` [tip:x86/cleanups] x86/e820: " tip-bot for Denys Vlasenko
2015-09-28 12:23 ` [PATCH] x86: Deinline early_console_register, save 403 bytes Denys Vlasenko
2015-09-30 19:57 ` [tip:x86/cleanups] " tip-bot for Denys Vlasenko
2015-09-28 12:23 ` [PATCH] x86/signal: Deinline get_sigframe, save 240 bytes Denys Vlasenko
2015-09-28 12:33 ` H. Peter Anvin
2015-09-28 13:43 ` Denys Vlasenko [this message]
2015-09-28 20:24 ` Davidlohr Bueso
2015-09-29 18:54 ` Thomas Gleixner
2015-09-30 19:58 ` [tip:x86/cleanups] " tip-bot for Denys Vlasenko
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