linux-kernel - Re: [PATCH 3/3] x86, extable: Handle early exceptions

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Message-ID: <CA+8MBbKz4GNs-mFj5=dCpRe_XLgoKZZz-8GM+FqTMTDBKqJNJw@mail.gmail.com>
Date:	Thu, 19 Apr 2012 15:47:28 -0700
From:	Tony Luck <tony.luck@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	David Daney <ddaney.cavm@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...64.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Daney <ddaney@...iumnetworks.com>
Subject: Re: [PATCH 3/3] x86, extable: Handle early exceptions

On Thu, Apr 19, 2012 at 3:16 PM, H. Peter Anvin <hpa@...or.com> wrote:
> One thing that probably would give more of a boost is to use a rbtree or
> similar structure to figure out *which* extable (if any) we should be
> looking at; right now it looks like we linearly walk the modules, and
> don't even look to see if we are inside that module before we do a
> bsearch in that module's extable...

How many entries are in the extable for a typical module?  Perhaps it might
make sense to bundle them all into one sorted combined table? Of course
you would have to have a way to squeeze them back out of the combined
table at module unload time.

This moves the cost to module load/unload time ... which is hopefully rare
compared to table lookup.

-Tony
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