Received-SPF: pass (google.com: domain of linux-kernel+bounces-65486-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Date: Wed, 14 Feb 2024 10:06:52 -0600
From: Bjorn Helgaas <helgaas@kernel.org>
To: Raag Jadav <raag.jadav@intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	bhelgaas@google.com, jarkko.nikula@linux.intel.com,
	mika.westerberg@linux.intel.com, stanislaw.gruszka@linux.intel.com,
	lukas@wunner.de, rafael@kernel.org, ilpo.jarvinen@linux.intel.com,
	linux-pci@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org,
	sashal@kernel.org
Subject: Re: [PATCH v1] PCI / PM: Really allow runtime PM without callback
 functions
Message-ID: <20240214160652.GA1254564@bhelgaas>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Zcy-I9-HcA_RuOyY@black.fi.intel.com>

On Wed, Feb 14, 2024 at 03:20:35PM +0200, Raag Jadav wrote:
> On Wed, Feb 14, 2024 at 03:01:29PM +0200, Andy Shevchenko wrote:
> > On Wed, Feb 14, 2024 at 12:43:35PM +0200, Raag Jadav wrote:
> > > On Tue, Feb 13, 2024 at 02:06:48PM -0600, Bjorn Helgaas wrote:
> > > > On Mon, Feb 12, 2024 at 12:02:33PM +0530, Raag Jadav wrote:
> > 
> > ...
> > 
> > > > >  0)               |  pm_runtime_work() {
> > > > >  0)               |    rpm_idle() {
> > > > >  0)               |      rpm_check_suspend_allowed() {
> > > > >  0)   1.500 us    |        __dev_pm_qos_resume_latency(); /* = 0x7fffffff */
> > > > >  0)   4.840 us    |      } /* rpm_check_suspend_allowed = 0x0 */
> > > > >  0)   1.550 us    |      __rpm_get_callback(); /* = 0xffffffffb4bc84f0 */
> > > > >  0)   1.800 us    |      pci_pm_runtime_idle(); /* = -38 */
> > > > >  0) + 17.070 us   |    } /* rpm_idle = -38 */
> > > > >  0) + 22.450 us   |  } /* pm_runtime_work = -38 */
> > > > 
> > > > What is this timing information telling me?
> > > 
> > > It's a raw ftrace dump.
> > 
> > (Told ya that people would be surprised with this without seeing how you get
> >  this and what fields mean)
> 
> I can add stat headers in v2 which I think will be more helpful.

That's not what I was asking.  *Why* is the ftrace dump here?  Is the
point that we're calling a function we shouldn't?  That this patch
improves performance?  Without some interpretation of what the dump
shows, it's just noise.

Bjorn