linux-kernel - Re: [v6] kvm/fpu: Enable fully eager restore kvm FPU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <553955D9.3030600@zytor.com>
Date:	Thu, 23 Apr 2015 13:28:09 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Dave Hansen <dave.hansen@...el.com>,
	Liang Li <liang.z.li@...el.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
CC:	gleb@...nel.org, pbonzini@...hat.com, mtosatt@...hat.com,
	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	joro@...tes.org, yang.z.zhang@...el.com,
	Xudong Hao <xudong.hao@...el.com>
Subject: Re: [v6] kvm/fpu: Enable fully eager restore kvm FPU

On 04/23/2015 08:28 AM, Dave Hansen wrote:
> On 04/23/2015 02:13 PM, Liang Li wrote:
>> When compiling kernel on westmere, the performance of eager FPU
>> is about 0.4% faster than lazy FPU.
> 
> Do you have an theory why this is?  What does the regression come from?
> 

This is interesting since previous measurements on KVM have had the
exact opposite results.  I think we need to understand this a lot more.

	-hpa


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/