From: Thomas Gleixner <tglx@linutronix.de>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
rjw@rjwysocki.net, mingo@redhat.com, bp@suse.de, x86@kernel.org,
linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-acpi@vger.kernel.org, peterz@infradead.org,
jolsa@redhat.com
Subject: Re: [PATCH v5 5/9] x86/sysctl: Add sysctl for ITMT scheduling feature
Date: Thu, 6 Oct 2016 13:13:08 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1610061307030.22338@nanos> (raw)
In-Reply-To: <1475684673.3916.299.camel@linux.intel.com>
[-- Attachment #1: Type: text/plain, Size: 1543 bytes --]
On Wed, 5 Oct 2016, Tim Chen wrote:
> On Wed, 2016-10-05 at 16:35 +0200, Thomas Gleixner wrote:
> > > + if (itmt_supported) {
> > > + itmt_sysctl_header =
> > > + register_sysctl_table(itmt_root_table);
> > > + if (!itmt_sysctl_header) {
> > > + mutex_unlock(&itmt_update_mutex);
> > > + return;
> > So you now have a state of capable which cannot be enabled. Whats the
> > point?
>
> For multi-socket system where ITMT is not enabled by default, the operator
> can still decide to enable it via sysctl.
With a sysctl which failed to be installed. Good luck with that.
> > > + }
> > > + /*
> > > + * ITMT capability automatically enables ITMT
> > > + * scheduling for small systems (single node).
> > > + */
> > > + if (topology_num_packages() == 1)
> > > + sysctl_sched_itmt_enabled = 1;
> > > + } else {
> > > + if (itmt_sysctl_header)
> > > + unregister_sysctl_table(itmt_sysctl_header);
> > > + }
> > > +
> > > + if (sysctl_sched_itmt_enabled) {
> > > + /* disable sched_itmt if we are no longer ITMT capable */
> > > + if (!itmt_supported)
> >
> > How do you get here if itmt is not supported?
>
> If the OS decides to turn off ITMT for any reason, (i.e. invoke
> sched_set_itmt_support(false) after it has turned on itmt_support
> before), this is the logic to do it. We don't turn off ITMT support
> after it has been turned on today, in the future the OS may.
Then please make this two functions (set/clear) so one can actually follow
the logic. The above is just too convoluted.
Thanks,
tglx
next prev parent reply other threads:[~2016-10-06 11:15 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-01 11:45 [PATCH v5 0/9] Support Intel® Turbo Boost Max Technology 3.0 Srinivas Pandruvada
2016-10-01 11:45 ` [PATCH v5 1/9] sched: Extend scheduler's asym packing Srinivas Pandruvada
2016-10-01 16:38 ` Nilay Vaish
2016-10-03 16:49 ` Tim Chen
2016-10-01 11:45 ` [PATCH v5 2/9] x86/topology: Provide topology_num_packages() Srinivas Pandruvada
2016-10-01 11:45 ` [PATCH v5 3/9] x86/topology: Define x86's arch_update_cpu_topology Srinivas Pandruvada
2016-10-01 11:45 ` [PATCH v5 4/9] x86: Enable Intel Turbo Boost Max Technology 3.0 Srinivas Pandruvada
2016-10-05 14:23 ` Thomas Gleixner
2016-10-05 16:05 ` Tim Chen
2016-10-01 11:45 ` [PATCH v5 5/9] x86/sysctl: Add sysctl for ITMT scheduling feature Srinivas Pandruvada
2016-10-05 14:35 ` Thomas Gleixner
2016-10-05 16:24 ` Tim Chen
2016-10-06 11:13 ` Thomas Gleixner [this message]
2016-10-06 17:37 ` Tim Chen
2016-10-12 16:50 ` Tim Chen
2016-10-01 11:45 ` [PATCH v5 6/9] x86/sched: Add SD_ASYM_PACKING flags to x86 ITMT CPU Srinivas Pandruvada
2016-10-01 11:45 ` [PATCH v5 7/9] acpi: bus: Enable HWP CPPC objects Srinivas Pandruvada
2016-10-01 11:45 ` [PATCH v5 8/9] acpi: bus: Set _OSC for diverse core support Srinivas Pandruvada
2016-10-01 11:45 ` [PATCH v5 9/9] cpufreq: intel_pstate: Use CPPC to get max performance Srinivas Pandruvada
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