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From: "H. Peter Anvin" <hpa@zytor.com>
To: David Daney <ddaney.cavm@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Borislav Petkov <bp@amd64.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	David Daney <ddaney@caviumnetworks.com>
Subject: Re: [PATCH 3/3] x86, extable: Handle early exceptions
Date: Thu, 19 Apr 2012 13:20:54 -0700	[thread overview]
Message-ID: <4F9073A6.4030709@zytor.com> (raw)
In-Reply-To: <4F9072CA.6030903@gmail.com>

On 04/19/2012 01:17 PM, David Daney wrote:
> On 04/19/2012 11:55 AM, H. Peter Anvin wrote:
>> Either way I suggest picking up David's presorting patchset since it
>> is already done and use its infrastructure for any further improvements.
> 
> It does have the advantage of already being implemented.  There was a
> little feedback on the kbuild portions of the patch.
> 
> If you would like, I will send an updated version of the patch.

Please.  It gets us 90% of the way, and we need the infrastructure
anyway to do any further work.

>> As far as a linear probe you get an average of n lookups with a
>> packing density of 1-1/n so you are right; a linear probe with a
>> density of say 1/2 is probably best.
>>
> 
> I usually see exception table sizes on the order of 2^10 entries, so I
> have to wonder how much you really gain from an O(1) implementation.

Well, for either variant of hash table you end up with ~2 serial memory
references as opposed to ~11.  No idea if there are workloads where this
actually matters.

	-hpa


  reply	other threads:[~2012-04-19 20:21 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-19  0:16 [PATCH 0/5] RFC: x86: Early exception table support H. Peter Anvin
2012-04-19  0:16 ` [PATCH 1/5] x86, nop: Make the ASM_NOP* macros work from assembly H. Peter Anvin
2012-04-19  9:29   ` Borislav Petkov
2012-04-20  0:24   ` [tip:x86/extable] " tip-bot for H. Peter Anvin
2012-04-19  0:16 ` [PATCH 2/5] x86: Add symbolic constant for exceptions with error code H. Peter Anvin
2012-04-19  9:30   ` Borislav Petkov
2012-04-20  0:25   ` [tip:x86/extable] " tip-bot for H. Peter Anvin
2012-04-19  0:16 ` [PATCH 3/5] x86, paravirt: Replace GET_CR2_INTO_RCX with GET_CR2_INTO_RAX H. Peter Anvin
2012-04-20  0:26   ` [tip:x86/extable] " tip-bot for H. Peter Anvin
2012-04-19  0:16 ` [PATCH 4/5] x86-64: Handle exception table entries during early boot H. Peter Anvin
2012-04-19 13:02   ` Borislav Petkov
2012-04-19 16:59     ` H. Peter Anvin
2012-04-19 17:16       ` Borislav Petkov
2012-04-20  0:29         ` [tip:x86/extable] x86, doc: Revert "x86: Document rdmsr_safe restrictions" tip-bot for H. Peter Anvin
2012-04-20  0:28   ` [tip:x86/extable] x86-64: Handle exception table entries during early boot tip-bot for H. Peter Anvin
2012-04-19  0:16 ` [PATCH 5/5] x86-32: " H. Peter Anvin
2012-04-20  0:28   ` [tip:x86/extable] " tip-bot for H. Peter Anvin
2012-04-19  9:22 ` [PATCH 0/5] RFC: x86: Early exception table support Borislav Petkov
2012-04-19  9:24   ` [PATCH 1/3] x86, extable: Cleanup fixup_exception Borislav Petkov
2012-04-19  9:25   ` [PATCH 2/3] x86, extable: Carve out the main extable searching routine Borislav Petkov
2012-04-19  9:26   ` [PATCH 3/3] x86, extable: Handle early exceptions Borislav Petkov
2012-04-19 17:02     ` H. Peter Anvin
2012-04-19 17:27       ` Linus Torvalds
2012-04-19 17:38         ` Borislav Petkov
2012-04-19 17:59           ` H. Peter Anvin
2012-04-19 18:25             ` Linus Torvalds
2012-04-19 18:55               ` H. Peter Anvin
2012-04-19 20:17                 ` David Daney
2012-04-19 20:20                   ` H. Peter Anvin [this message]
2012-04-19 20:26                     ` H. Peter Anvin
2012-04-19 20:40                       ` David Daney
2012-04-19 21:47                       ` Linus Torvalds
2012-04-19 22:16                   ` H. Peter Anvin
2012-04-19 22:47                     ` Tony Luck
2012-04-19 22:58                       ` Linus Torvalds
2012-04-19 23:10                         ` H. Peter Anvin
2012-04-19 23:26                           ` Tony Luck
2012-04-19 23:35                             ` H. Peter Anvin
2012-04-20  8:26                             ` Andreas Schwab
2012-04-19 18:11           ` Linus Torvalds
2012-04-20  8:46             ` Borislav Petkov
2012-04-19 17:54       ` H. Peter Anvin
2012-04-20  0:27 ` [tip:x86/extable] x86, extable: Add early_fixup_exception() tip-bot for H. Peter Anvin

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