From: Peter Zijlstra <peterz@infradead.org>
To: Vince Weaver <vincent.weaver@maine.edu>
Cc: mingo@kernel.org, eranian@google.com,
alexander.shishkin@linux.intel.com, acme@redhat.com,
hpa@zytor.com, torvalds@linux-foundation.org, tglx@linutronix.de,
linux-kernel@vger.kernel.org, jolsa@redhat.com,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perf/core] perf/x86/intel: Force resched when TFA sysctl is modified
Date: Tue, 16 Apr 2019 19:41:10 +0200 [thread overview]
Message-ID: <20190416174110.GS4038@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.DEB.2.21.1904161227001.20764@macbook-air>
On Tue, Apr 16, 2019 at 12:28:00PM -0400, Vince Weaver wrote:
> On Tue, 16 Apr 2019, tip-bot for Stephane Eranian wrote:
>
> > Commit-ID: f447e4eb3ad1e60d173ca997fcb2ef2a66f12574
> > Gitweb: https://git.kernel.org/tip/f447e4eb3ad1e60d173ca997fcb2ef2a66f12574
> > Author: Stephane Eranian <eranian@google.com>
> > AuthorDate: Mon, 8 Apr 2019 10:32:52 -0700
> > Committer: Ingo Molnar <mingo@kernel.org>
> > CommitDate: Tue, 16 Apr 2019 12:19:35 +0200
> >
> > perf/x86/intel: Force resched when TFA sysctl is modified
>
> What's TFA? Tuna-fish-alarm? Nowhere in the commit or in the code does
> it ever say what a TFA is or why we'd want to resched when it is modified.
See commit: 400816f60c54 ("perf/x86/intel: Implement support for TSX Force Abort")
Author: Peter Zijlstra (Intel) <peterz@infradead.org>
Date: Tue Mar 5 22:23:18 2019 +0100
perf/x86/intel: Implement support for TSX Force Abort
Skylake (and later) will receive a microcode update to address a TSX
errata. This microcode will, on execution of a TSX instruction
(speculative or not) use (clobber) PMC3. This update will also provide
a new MSR to change this behaviour along with a CPUID bit to enumerate
the presence of this new MSR.
When the MSR gets set; the microcode will no longer use PMC3 but will
Force Abort every TSX transaction (upon executing COMMIT).
When TSX Force Abort (TFA) is allowed (default); the MSR gets set when
PMC3 gets scheduled and cleared when, after scheduling, PMC3 is
unused.
When TFA is not allowed; clear PMC3 from all constraints such that it
will not get used.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
next prev parent reply other threads:[~2019-04-16 17:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-08 17:32 [PATCH v2 0/3] perf/x86/intel: force reschedule on TFA changes Stephane Eranian
2019-04-08 17:32 ` [PATCH v2 1/2] perf/core: add perf_ctx_resched() as global function Stephane Eranian
2019-04-15 15:45 ` Peter Zijlstra
2019-04-15 15:53 ` Peter Zijlstra
2019-04-16 11:33 ` [tip:perf/core] perf/core: Add perf_pmu_resched() " tip-bot for Stephane Eranian
2019-04-08 17:32 ` [PATCH v2 2/2] perf/x86/intel: force resched when TFA sysctl is modified Stephane Eranian
2019-04-15 15:57 ` Peter Zijlstra
2019-04-15 17:20 ` Stephane Eranian
2019-04-16 11:33 ` [tip:perf/core] perf/x86/intel: Force " tip-bot for Stephane Eranian
2019-04-16 16:28 ` Vince Weaver
2019-04-16 17:41 ` Peter Zijlstra [this message]
2019-04-17 6:06 ` Ingo Molnar
2019-04-18 21:50 ` Stephane Eranian
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