From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: linux-arch@vger.kernel.org, "Juergen Gross" <jgross@suse.com>,
"Jeremy Fitzhardinge" <jeremy@goop.org>,
x86@kernel.org, kvm@vger.kernel.org,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Pan Xinhui" <xinhui.pan@linux.vnet.ibm.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
"Chris Wright" <chrisw@sous-sol.org>,
"Ingo Molnar" <mingo@redhat.com>,
hpa@zytor.com, xen-devel@lists.xenproject.org,
"Alok Kataria" <akataria@vmware.com>,
"Thomas Gleixner" <tglx@linutronix.de>
Subject: Re: [PATCH v2] x86/paravirt: Don't make vcpu_is_preempted() a callee-save function
Date: Mon, 13 Feb 2017 23:31:30 +0100 [thread overview]
Message-ID: <20170213223130.GL6500@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <19008130-7b73-5c53-3cb5-a013e9e5552b@redhat.com>
On Mon, Feb 13, 2017 at 05:24:36PM -0500, Waiman Long wrote:
> >> movsql %edi, %rax;
> >> movq __per_cpu_offset(,%rax,8), %rax;
> >> cmpb $0, %[offset](%rax);
> >> setne %al;
> I have thought of that too. However, the goal is to eliminate memory
> read/write from/to stack. Eliminating a register sign-extend instruction
> won't help much in term of performance.
Problem here is that all instructions have dependencies, so if you can
get rid of the sign extend mov you kill a bunch of stall cycles (I would
expect).
But yes, peanuts vs the stack load/stores.
next prev parent reply other threads:[~2017-02-13 22:31 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-10 15:43 [PATCH v2] x86/paravirt: Don't make vcpu_is_preempted() a callee-save function Waiman Long
2017-02-10 16:19 ` Peter Zijlstra
2017-02-10 16:35 ` Waiman Long
2017-02-10 17:00 ` Waiman Long
2017-02-13 10:47 ` Peter Zijlstra
2017-02-13 10:53 ` Peter Zijlstra
2017-02-13 19:42 ` Waiman Long
2017-02-13 20:12 ` Waiman Long
2017-02-13 21:52 ` Peter Zijlstra
2017-02-13 22:00 ` hpa
2017-02-13 22:07 ` hpa
2017-02-13 22:34 ` Waiman Long
2017-02-13 22:36 ` hpa
2017-02-14 9:39 ` Peter Zijlstra
2017-02-14 14:46 ` Waiman Long
2017-02-14 16:03 ` Peter Zijlstra
2017-02-14 16:18 ` [Xen-devel] " Andrew Cooper
2017-02-13 20:06 ` hpa
2017-02-13 21:57 ` Peter Zijlstra
2017-02-13 22:24 ` Waiman Long
2017-02-13 22:31 ` Peter Zijlstra [this message]
2017-02-13 19:41 ` Waiman Long
2017-02-10 16:22 ` Paolo Bonzini
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