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From: Andrew Lutomirski <luto@mit.edu>
To: Ingo Molnar <mingo@elte.hu>
Cc: x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org, Jesper Juhl <jj@chaosbits.net>,
	Borislav Petkov <bp@alien8.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Arjan van de Ven <arjan@infradead.org>,
	Jan Beulich <JBeulich@novell.com>,
	richard -rw- weinberger <richard.weinberger@gmail.com>,
	Mikael Pettersson <mikpe@it.uu.se>
Subject: Re: [PATCH v2 08/10] x86-64: Emulate vsyscalls
Date: Mon, 30 May 2011 07:35:33 -0400	[thread overview]
Message-ID: <BANLkTimhMuN03qABgs0+Z+yti-rco5V82Q@mail.gmail.com> (raw)
In-Reply-To: <20110530105937.GB20133@elte.hu>

On Mon, May 30, 2011 at 6:59 AM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Andrew Lutomirski <luto@mit.edu> wrote:
>
>>
>> I'd advocate waiting until glibc 2.14 comes out with this change:
>>
>> http://sourceware.org/git/?p=glibc.git;a=commit;h=a8509ca540427502bd955f35296ff7b727c7a8a1
>>
>> I want to add a warning (ratelimited to an extremely low rate) in v3
>> whenever any of the vsyscalls get used telling users that their legacy
>> code is suffering a performance impact, but it seems like bad form to
>> tell people to build glibc from git to avoid a regression.
>
> But only statically built binaries would be impacted in practice,
> right? The number of statically built binaries that heavily rely on
> vsyscalls ought to be a very small set ...

With current glibc even dynamic binaries take the hit on time().

With the emulation warning (coming in v3), I get (on a Fedora 15-based VM):

[    0.635493] init[1] emulated legacy vsyscall time(); upgrade your
code to avoid a performance hit. ip:ffffffffff600404 sp:7fff277fe9c8
caller:3da3e9e27d in libc.so.6[3da3e00000+192000]

--Andy

  reply	other threads:[~2011-05-30 11:35 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-30  3:48 [PATCH v2 00/10] Remove syscall instructions at fixed addresses Andy Lutomirski
2011-05-30  3:48 ` [PATCH v2 01/10] x86-64: Fix alignment of jiffies variable Andy Lutomirski
2011-05-30  3:48 ` [PATCH v2 02/10] x86-64: Give vvars their own page Andy Lutomirski
2011-05-30  3:48 ` [PATCH v2 03/10] x86-64: Remove kernel.vsyscall64 sysctl Andy Lutomirski
2011-05-30  3:48 ` [PATCH v2 04/10] x86-64: Replace vsyscall gettimeofday fallback with int 0xcc Andy Lutomirski
2011-05-30  3:48 ` [PATCH v2 05/10] x86-64: Map the HPET NX Andy Lutomirski
2011-05-30  3:48 ` [PATCH v2 06/10] x86-64: Remove vsyscall number 3 (venosys) Andy Lutomirski
2011-05-30  3:48 ` [PATCH v2 07/10] x86-64: Fill unused parts of the vsyscall page with 0xcc Andy Lutomirski
2011-05-30  3:48 ` [PATCH v2 08/10] x86-64: Emulate vsyscalls Andy Lutomirski
2011-05-30  7:35   ` Borislav Petkov
2011-05-30 10:43     ` Andrew Lutomirski
2011-05-30  7:46   ` Ingo Molnar
2011-05-30 10:57     ` Andrew Lutomirski
2011-05-30 10:59       ` Ingo Molnar
2011-05-30 11:35         ` Andrew Lutomirski [this message]
2011-05-30 12:15           ` Ingo Molnar
2011-05-30 12:25             ` Andrew Lutomirski
2011-05-30 14:12               ` Ingo Molnar
2011-05-30  7:51   ` Jan Beulich
2011-05-30  8:07     ` Ingo Molnar
2011-05-31  2:29     ` Andrew Lutomirski
2011-05-30  3:48 ` [PATCH v2 09/10] x86-64: Randomize int 0xcc magic al values at boot Andy Lutomirski
2011-05-30  3:48 ` [PATCH v2 10/10] x86-64: Document some of entry_64.S Andy Lutomirski
2011-05-30  7:59   ` Borislav Petkov
2011-05-30 10:40     ` Andrew Lutomirski
2011-05-30 10:50       ` Ingo Molnar

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