From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: marcel.a@redhat.com, qemu-devel@nongnu.org, lcapitulino@redhat.com
Subject: Re: [Qemu-devel] [PATCH 0/2] exec: alternative fix for master abort woes
Date: Mon, 11 Nov 2013 17:57:54 +0100 [thread overview]
Message-ID: <52810C92.7080500@redhat.com> (raw)
In-Reply-To: <20131111164309.GA23604@redhat.com>
Il 11/11/2013 17:43, Michael S. Tsirkin ha scritto:
> On Thu, Nov 07, 2013 at 06:29:40PM +0100, Paolo Bonzini wrote:
>> Il 07/11/2013 17:47, Michael S. Tsirkin ha scritto:
>>> That's on kvm with 52 bit address.
>>> But where I would be concerned is systems with e.g. 36 bit address
>>> space where we are doubling the cost of the lookup.
>>> E.g. try i386 and not x86_64.
>>
>> Tried now...
>>
>> P_L2_LEVELS pre-patch post-patch
>> i386 3 6
>> x86_64 4 6
>>
>> I timed the inl_from_qemu test of vmexit.flat with both KVM and TCG. With
>> TCG there's indeed a visible penalty of 20 cycles for i386 and 10 for x86_64
>> (you can extrapolate to 30 cycles for TARGET_PHYS_ADDR_SPACE_BITS=32 targets).
>
> So how did you measure this exactly?
I mention extrapolation because x86 is TARGET_PHYS_ADDR_SPACE_BITS=36,
not 32.
Paolo
prev parent reply other threads:[~2013-11-11 16:58 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-07 16:14 [Qemu-devel] [PATCH 0/2] exec: alternative fix for master abort woes Paolo Bonzini
2013-11-07 16:14 ` [Qemu-devel] [PATCH 1/2] split definitions for exec.c and translate-all.c radix trees Paolo Bonzini
2013-11-07 16:14 ` [Qemu-devel] [PATCH 2/2] exec: make address spaces 64-bit wide Paolo Bonzini
2013-11-10 10:31 ` Michael S. Tsirkin
2013-11-11 10:15 ` Paolo Bonzini
2013-11-07 16:21 ` [Qemu-devel] [PATCH 0/2] exec: alternative fix for master abort woes Michael S. Tsirkin
2013-11-07 16:29 ` Paolo Bonzini
2013-11-07 16:47 ` Michael S. Tsirkin
2013-11-07 17:29 ` Paolo Bonzini
2013-11-07 18:54 ` Michael S. Tsirkin
2013-11-07 19:12 ` Paolo Bonzini
2013-11-11 16:43 ` Michael S. Tsirkin
2013-11-11 16:57 ` Paolo Bonzini [this message]
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