From: Keir Fraser <keir@xen.org>
To: Jan Beulich <JBeulich@novell.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Subject: Re: [PATCH] Enble 6 argument hypercalls for HVMs
Date: Wed, 15 Dec 2010 13:20:46 +0000 [thread overview]
Message-ID: <C92E712E.CF5C%keir@xen.org> (raw)
In-Reply-To: <4D08BEA102000078000281FE@vpn.id2.novell.com>
On 15/12/2010 12:12, "Jan Beulich" <JBeulich@novell.com> wrote:
>>>> On 15.12.10 at 12:43, Keir Fraser <keir@xen.org> wrote:
>> On 15/12/2010 10:40, "Jan Beulich" <JBeulich@novell.com> wrote:
>>> Looking at this code also makes me wonder once again whether
>>> it really is a good idea to have a generally not taken forward
>>> branch here.
>>
>> Which generally not-taken branch? The 'je 1f' instruction generally *will*
>> be taken!
>
> Oops, of course - it being taken is the problem, as it'll be statically
> mis-predicted.
Well, moving the trace code out of line, perhaps into the fixup section,
would be good for cache locality. And then we would have a rarely taken
forward branch (since the fixup section comes after normal text).
I'm sure there are a bunch of places in our asm code where we could do this.
Feel free to fix them all up, if you like.
-- Keir
> Jan
>
prev parent reply other threads:[~2010-12-15 13:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-14 22:16 [PATCH] Enble 6 argument hypercalls for HVMs Ross Philipson
2010-12-15 9:07 ` Jan Beulich
2010-12-15 10:06 ` Keir Fraser
2010-12-15 10:40 ` Jan Beulich
2010-12-15 11:43 ` Keir Fraser
2010-12-15 12:12 ` Jan Beulich
2010-12-15 13:20 ` Keir Fraser [this message]
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