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From: Ingo Molnar <mingo@elte.hu>
To: pageexec@freemail.hu
Cc: Andrew Lutomirski <luto@mit.edu>,
	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>,
	Andi Kleen <andi@firstfloor.org>, Brian Gerst <brgerst@gmail.com>,
	Louis Rilling <Louis.Rilling@kerlabs.com>,
	Valdis.Kletnieks@vt.edu
Subject: Re: [PATCH v5 8/9] x86-64: Emulate legacy vsyscalls
Date: Mon, 6 Jun 2011 17:26:57 +0200
Message-ID: <20110606152657.GJ30348@elte.hu> (raw)
In-Reply-To: <4DECDD14.5845.12BA3C18@pageexec.freemail.hu>


* pageexec@freemail.hu <pageexec@freemail.hu> wrote:

> > > a page fault is never a fast path, after all the cpu has just 
> > > taken an exception (vs. the syscall/sysenter style actually 
> > > fast user->kernel transition) and is about to make page table 
> > > changes (and possibly TLB flushes).
> >
> > Sure it is.  It's a path that's optimized carefully and needs to 
> > be as fast as possible.  Just because it's annoyingly slow 
> > doesn't mean we get to make it even slower.
> 
> sorry, but stating that the pf handler is a fast path doesn't make 
> it so ;) [...]

Are you talking about the Linux kernel?

FYI, incredible amount of work has gone into making pagefaults as 
fast and scalable as possible. If you are following Linux kernel 
development you'd have to be virtually blind to not see all that 
effort.

[ And yes, serious amount of work has gone into the hardware side as
  well - P4's used to suck *really* bad at pagefaults. ]

You claiming that pagefaults are a slow-path and ridiculing those who 
point out your mistake does not make it a slowpath.

Thanks,

	Ingo

  parent reply index

Thread overview: 112+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-05 17:50 [PATCH v5 0/9] Remove syscall instructions at fixed addresses Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 1/9] x86-64: Fix alignment of jiffies variable Andy Lutomirski
2011-06-06  8:31   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 2/9] x86-64: Document some of entry_64.S Andy Lutomirski
2011-06-06  8:31   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 3/9] x86-64: Give vvars their own page Andy Lutomirski
2011-06-06  8:32   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 4/9] x86-64: Remove kernel.vsyscall64 sysctl Andy Lutomirski
2011-06-06  8:32   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-12-05 18:27   ` [PATCH v5 4/9] " Matthew Maurer
2011-06-05 17:50 ` [PATCH v5 5/9] x86-64: Map the HPET NX Andy Lutomirski
2011-06-06  8:33   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 6/9] x86-64: Remove vsyscall number 3 (venosys) Andy Lutomirski
2011-06-06  8:33   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 7/9] x86-64: Fill unused parts of the vsyscall page with 0xcc Andy Lutomirski
2011-06-06  8:34   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 8/9] x86-64: Emulate legacy vsyscalls Andy Lutomirski
2011-06-05 19:30   ` Ingo Molnar
2011-06-05 20:01     ` Andrew Lutomirski
2011-06-06  7:39       ` Ingo Molnar
2011-06-06  9:42       ` pageexec
2011-06-06 11:19         ` Andrew Lutomirski
2011-06-06 11:56           ` pageexec
2011-06-06 12:43             ` Andrew Lutomirski
2011-06-06 13:58               ` pageexec
2011-06-06 14:07                 ` Brian Gerst
2011-06-07 23:32                   ` pageexec
2011-06-07 23:49                     ` Andrew Lutomirski
2011-06-08  6:32                       ` pageexec
2011-06-06 15:26                 ` Ingo Molnar [this message]
2011-06-06 15:48                   ` pageexec
2011-06-06 15:59                     ` Ingo Molnar
2011-06-06 16:19                       ` pageexec
2011-06-06 16:47                         ` Ingo Molnar
2011-06-06 22:49                           ` pageexec
2011-06-06 22:57                             ` david
2011-06-07  9:07                               ` Ingo Molnar
2011-06-07  6:59                             ` Pekka Enberg
2011-06-07  8:30                             ` Ingo Molnar
2011-06-07 23:24                               ` pageexec
2011-06-08  5:55                                 ` Pekka Enberg
2011-06-08  6:19                                   ` pageexec
2011-06-08  6:48                                 ` Ingo Molnar
2011-06-08  9:02                                   ` pageexec
2011-06-08  9:11                                     ` Andi Kleen
2011-06-08  9:35                                       ` pageexec
2011-06-08 10:06                                         ` Andi Kleen
2011-06-08 10:26                                           ` pageexec
2011-06-08 10:39                                             ` Ingo Molnar
2011-06-08 10:35                                           ` Ingo Molnar
2011-06-08  9:15                                     ` Ingo Molnar
2011-06-08  7:16                                 ` Ingo Molnar
2011-06-08  9:29                                   ` pageexec
2011-06-06 14:01             ` Linus Torvalds
2011-06-06 14:55               ` pageexec
2011-06-06 15:33                 ` Ingo Molnar
2011-06-06 15:58                   ` pageexec
2011-06-06 15:41         ` Ingo Molnar
2011-06-06  8:34   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-06  8:35   ` [tip:x86/vdso] x86-64, vdso, seccomp: Fix !CONFIG_SECCOMP build tip-bot for Ingo Molnar
2011-06-07  7:49   ` [tip:x86/vdso] x86-64: Emulate legacy vsyscalls tip-bot for Andy Lutomirski
2011-06-07  8:03   ` tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 9/9] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to feature-removal-schedule Andy Lutomirski
2011-06-06  8:34   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-06  8:46   ` [PATCH v5 9/9] " Linus Torvalds
2011-06-06  9:31     ` Andi Kleen
2011-06-06 10:39       ` pageexec
2011-06-06 13:56         ` Linus Torvalds
2011-06-06 18:46           ` pageexec
2011-06-06 20:40             ` Linus Torvalds
2011-06-06 20:51               ` Andrew Lutomirski
2011-06-06 21:54                 ` Ingo Molnar
2011-06-06 21:45               ` Ingo Molnar
2011-06-06 21:48                 ` Ingo Molnar
     [not found]                 ` <BANLkTi==uw_h78oaep1cCOCzwY0edLUU_Q@mail.gmail.com>
2011-06-07  8:03                   ` [PATCH, v6] x86-64: Emulate legacy vsyscalls Ingo Molnar
2011-06-06 21:53               ` [PATCH v5 9/9] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to feature-removal-schedule pageexec
2011-06-06 14:44         ` Ingo Molnar
2011-06-06 15:01           ` pageexec
2011-06-06 15:15             ` Ingo Molnar
2011-06-06 15:29               ` pageexec
2011-06-06 16:54                 ` Ingo Molnar
2011-06-06 18:59           ` pageexec
2011-06-06 19:25             ` Ingo Molnar
2011-06-07  0:34               ` pageexec
2011-06-07  9:51                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-10 11:19                     ` Ingo Molnar
2011-06-14  0:48                       ` pageexec
2011-06-15 19:42                         ` Valdis.Kletnieks
2011-06-06 14:52         ` Ingo Molnar
2011-06-06 10:24     ` [PATCH] x86-64, vsyscalls: Rename UNSAFE_VSYSCALLS to COMPAT_VSYSCALLS Ingo Molnar
2011-06-06 11:20       ` pageexec
2011-06-06 12:47         ` Ingo Molnar
2011-06-06 12:48           ` Ingo Molnar
2011-06-06 18:04           ` pageexec
2011-06-06 19:12             ` Ingo Molnar
2011-06-07  0:02               ` pageexec
2011-06-07  9:56                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-09  6:48                     ` Ingo Molnar
2011-06-09 23:33                       ` pageexec
2011-06-07 10:05                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-09  7:02                     ` Ingo Molnar
2011-06-09 23:33                       ` pageexec
2011-06-07 10:13                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-06 12:19       ` Ted Ts'o
2011-06-06 12:33         ` Andrew Lutomirski
2011-06-06 12:37         ` Ingo Molnar
2011-06-06 14:34     ` [tip:x86/vdso] " tip-bot for Ingo Molnar
2011-06-05 20:05 ` [PATCH v5 0/9] Remove syscall instructions at fixed addresses Andrew Lutomirski

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