From: "H. Peter Anvin" <hpa@zytor.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Sebastian Lackner <sebastian@fds-team.de>,
X86 ML <x86@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
Anish Bhatt <anish@chelsio.com>, Ingo Molnar <mingo@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Chuck Ebbert <cebbert.lkml@gmail.com>,
stable <stable@vger.kernel.org>
Subject: Re: [PATCH v2 1/2] x86_64,entry: Filter RFLAGS.NT on entry from userspace
Date: Wed, 01 Oct 2014 09:17:26 -0700 [thread overview]
Message-ID: <542C2916.7010500@zytor.com> (raw)
In-Reply-To: <CALCETrXWL7ze+7Y7ZHT8j8eZqJb_uRsA1PZsuzSu2cJV0tFgog@mail.gmail.com>
On 10/01/2014 09:04 AM, Andy Lutomirski wrote:
>
> Agner Fog's tables for Sandy Bridge have 9 uops for popf and
> reciprocal throughput 18. sti isn't listed for Sandy Bridge or
> anything similar, but cld is 3 uops with reciprocal throughput 4.
> Also, popf accesses rsp, and the sysenter code is very heavy on stack
> manipulation.
>
It does a stack operation. Newer CPUs optimize stack accesses pretty
heavily. That doesn't mean back-to-back push/pop are all that
optimized, I wonder if it would help separating them. popf is unlikely
to ever be all that fast.
-hpa
next prev parent reply other threads:[~2014-10-01 16:17 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-01 4:51 [PATCH v2 0/2] x86_64,entry: Clear NT on entry and speed up switch_to Andy Lutomirski
2014-10-01 4:51 ` [PATCH v2 1/2] x86_64,entry: Filter RFLAGS.NT on entry from userspace Andy Lutomirski
2014-10-01 5:09 ` Sebastian Lackner
2014-10-01 5:24 ` Andy Lutomirski
2014-10-01 15:19 ` H. Peter Anvin
2014-10-01 14:09 ` Chuck Ebbert
2014-10-01 14:32 ` Chuck Ebbert
2014-10-01 14:46 ` Andy Lutomirski
2014-10-01 14:56 ` Chuck Ebbert
2014-10-01 15:03 ` Andy Lutomirski
2014-10-01 15:22 ` H. Peter Anvin
2014-10-01 15:26 ` H. Peter Anvin
2014-10-01 15:50 ` Andy Lutomirski
2014-10-01 16:04 ` Andy Lutomirski
2014-10-01 16:17 ` H. Peter Anvin [this message]
2014-10-01 4:51 ` [PATCH v2 2/2] x86_64: Don't save flags on context switch Andy Lutomirski
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