WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] [PATCH][RFC] FPU LWP 0/5: patch description

To: Wei Huang <wei.huang2@xxxxxxx>, "'xen-devel@xxxxxxxxxxxxxxxxxxx'" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH][RFC] FPU LWP 0/5: patch description
From: Keir Fraser <keir.xen@xxxxxxxxx>
Date: Thu, 14 Apr 2011 22:09:59 +0100
Cc:
Delivery-date: Thu, 14 Apr 2011 14:11:50 -0700
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:user-agent:date:subject:from:to:message-id :thread-topic:thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; bh=wG31yYTCf4WYZt66m6yg6mT6khYhzfZTc6kWTYauJq0=; b=vz07TGfcGCzzLh5UssRu/eKWe/OdrkQMoA5M7esV2RZmMbcePtr+0/8OyAx+SfuBTf 5/N0Yty03X27+BaY9X82L/7ThckQqOVhBYGKDRvLzDboYaraBaPnzPrZnOnhP4eaUDtq ASDQD7emIxqVpbUDUIWC0E33FSU8bo+W+kbaU=
Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=user-agent:date:subject:from:to:message-id:thread-topic :thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; b=vp/W7xRLtagb5y/uhb9oPQ635ExUAi0TjZYGC5Ye5VweUzsamn19neFS35oILw6oJa HpGGUjAr+XT91jZi4z08mtOCQAbFYqXVcuLe80pzXFi2ulbOg8CrmitNv37VtgFVGkwc +Kbs5CIpaumpnCJ10PvBxKUjUJXra7yijX6CU=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4DA75B07.6010503@xxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: Acv66E/ls51O2N5kzE6rYZoAw5tFww==
Thread-topic: [Xen-devel] [PATCH][RFC] FPU LWP 0/5: patch description
User-agent: Microsoft-Entourage/12.28.0.101117
On 14/04/2011 21:37, "Wei Huang" <wei.huang2@xxxxxxx> wrote:

> The following patches support AMD lightweight profiling.
> 
> Because LWP isn't tracked by CR0.TS bit, we clean up the FPU code to
> handle lazy and unlazy FPU states differently. Lazy FPU state (such as
> SSE, YMM) is handled when #NM is triggered. Unlazy state, such as LWP,
> is saved and restored on each vcpu context switch. To simplify the code,
> we also add a mask option to xsave/xrstor function.

How much cost is added to context switch paths in the (overwhelmingly
likely) case that LWP is not being used by the guest? Is this adding a whole
lot of unconditional overhead for a feature that noone uses?

 -- Keir

> Thanks,
> -Wei
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel