From: Bjorn Helgaas <helgaas@kernel.org>
To: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Lukas Wunner <lukas@wunner.de>,
Chris Chiu <chris.chiu@canonical.com>,
Alexander Motin <mav@ixsystems.com>,
Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>,
linux-pci@vger.kernel.org
Subject: Re: [PATCH v4 1/2] PCI: Take other bus devices into account when distributing resources
Date: Thu, 5 Jan 2023 11:04:13 -0600 [thread overview]
Message-ID: <20230105170413.GA1150738@bhelgaas> (raw)
In-Reply-To: <Y7bUAaxt6viswdXV@black.fi.intel.com>
On Thu, Jan 05, 2023 at 03:43:29PM +0200, Mika Westerberg wrote:
> On Thu, Jan 05, 2023 at 11:12:11AM +0200, Mika Westerberg wrote:
> > > What happens in a topology like this:
> > >
> > > 10:00.0 non-hotplug bridge to [bus 20-3f]
> > > 10:01.0 non-hotplug bridge to [bus 40]
> > > 20:00.0 hotplug bridge
> > > 40:00.0 NIC
> > >
> > > where we're distributing space on "bus" 10, hotplug_bridges == 0 and
> > > normal_bridges == 2? Do we give half the extra space to bus 20 and
> > > the other half to bus 40, even though we could tell up front that bus
> > > 20 is the only place that can actually use any extra space?
> >
> > Yes we split it into half.
>
> Forgot to reply also that would it make sense here to look at below the
> non-hotplug bridges and if we find hotplug bridges, distribute the space
> equally between those or something like that?
Yes, I do think ultimately it would make sense to keep track at every
bridge whether it or any descendant is a hotplug bridge so we could
distribute extra space only to bridges that could potentially use it.
But I don't know if that needs to be done in this series. This code
is so complicated and fragile that I think being ruthless about
defining the minimal problem we're solving and avoiding scope creep
will improve our chances of success.
So treat this as a question to improve my understanding more than
anything.
Bjorn
next prev parent reply other threads:[~2023-01-05 17:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-04 9:16 [PATCH v4 0/2] PCI: distribute resources for root buses Mika Westerberg
2023-01-04 9:16 ` [PATCH v4 1/2] PCI: Take other bus devices into account when distributing resources Mika Westerberg
2023-01-04 22:48 ` Bjorn Helgaas
2023-01-05 9:12 ` Mika Westerberg
2023-01-05 13:43 ` Mika Westerberg
2023-01-05 17:04 ` Bjorn Helgaas [this message]
2023-01-09 11:11 ` Mika Westerberg
2023-01-09 18:27 ` Alexander Motin
2023-01-10 10:07 ` Mika Westerberg
2023-01-09 19:33 ` Alexander Motin
2023-01-10 9:54 ` Mika Westerberg
2023-01-04 9:16 ` [PATCH v4 2/2] PCI: Distribute available resources for root buses too Mika Westerberg
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