From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: The killing of ideal_nops[]
Date: Wed, 10 Mar 2021 09:13:24 -0500 [thread overview]
Message-ID: <20210310091324.0c346d5f@oasis.local.home> (raw)
In-Reply-To: <YEid+HQnqgnt3iyY@hirez.programming.kicks-ass.net>
On Wed, 10 Mar 2021 11:22:48 +0100
Peter Zijlstra <peterz@infradead.org> wrote:
> After this FEATURE_NOPL is unused except for required-features for
> x86_64. FEATURE_K8 is only used for PTI and FEATURE_K7 is unused.
>
> AFAICT this negatively affects lots of 32bit (DONTCARE) and 32bit on
> 64bit CPUs (CARELESS) and early AMD (K8) which is from 2003 and almost
> 2 decades old by now (SHRUG).
>
> Everything x86_64 since AMD K10 (2007) was using p6_nops.
>
> And per FEATURE_NOPL being required for x86_64, all those CPUs can use
> p6_nops. So stop caring about NOPs, simplify things and get on with life
> :-)
Before ripping out all the ideal_nop logic, I wonder if we should just
force the nops you want now (that is, don't change the selected
ideal_nops, just "pretend" that the CPU wants p6_nops), and see if anyone
complains. After a few releases, if there's no complaints, then we can
rip out the ideal_nop logic.
-- Steve
next prev parent reply other threads:[~2021-03-10 14:14 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-09 16:58 The killing of ideal_nops[] Peter Zijlstra
2021-03-09 17:05 ` Steven Rostedt
2021-03-09 21:24 ` Peter Zijlstra
2021-03-10 0:33 ` hpa
2021-03-10 9:14 ` Peter Zijlstra
2021-03-10 9:35 ` Peter Zijlstra
2021-03-10 10:03 ` Peter Zijlstra
2021-03-10 10:22 ` Peter Zijlstra
2021-03-10 14:13 ` Steven Rostedt [this message]
2021-03-10 14:24 ` Peter Zijlstra
2021-03-10 14:30 ` Peter Zijlstra
2021-03-10 15:48 ` Alexei Starovoitov
2021-03-10 16:04 ` Peter Zijlstra
2021-03-11 9:28 ` David Laight
2021-03-14 22:43 ` Maciej W. Rozycki
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