From: Alexander Gordeev <agordeev@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
Joerg Roedel <joro@8bytes.org>, "x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
Jan Beulich <JBeulich@suse.com>,
Bjorn Helgaas <bhelgaas@google.com>,
linuxppc-dev@lists.ozlabs.org, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v2 2/6] PCI/MSI: Factor out pci_get_msi_cap() interface
Date: Thu, 26 Sep 2013 16:39:02 +0200 [thread overview]
Message-ID: <20130926143901.GE16774@dhcp-26-207.brq.redhat.com> (raw)
In-Reply-To: <20130926131147.GA31249@mtj.dyndns.org>
On Thu, Sep 26, 2013 at 09:11:47AM -0400, Tejun Heo wrote:
> > Because otherwise we will re-introduce a problem described by Michael:
> > "We have a small number of MSIs available, limited by hardware &
> > firmware, if we don't impose a quota then the first device that probes
> > will get most/all of the MSIs and other devices miss out."
>
> Still not following. Why wouldn't just letting the drivers request
> the optimal number they want and falling back to single interrupt mode
> work? ie. why can't we just have an all or nothing interface?
I can imagine a scenario where the first device probes in, requests its
optimal number, acquires that number and exhausts MSIs in pSeries firmware.
The next few devices possibly end up with single MSI, since no MSIs left
to satisfy their optimal numbers. If one of those single-MSI'ed devices
happened to be a high-performance HBA hitting a degraded performance that
alone would force (IBM) to introduce the quotas. Now, if the same/another
device happened does not support the legacy interrupt mode and no MSI
resources have left in the platform firmware at all...
> tejun
--
Regards,
Alexander Gordeev
agordeev@redhat.com
next prev parent reply other threads:[~2013-09-26 14:37 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20130905150259.GA30984@dhcp-26-207.brq.redhat.com>
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[not found] ` <CAErSpo4TU2geqzY3AYsL08KimBqtfwa4iUoFHgcFt0zMTBJkHw@mail.gmail.com>
[not found] ` <20130906160621.GF22763@mtj.dyndns.org>
[not found] ` <20130906233205.GF12956@google.com>
[not found] ` <20130909152044.GA24962@dhcp-26-207.brq.redhat.com>
2013-09-16 10:22 ` [PATCH v2 2/6] PCI/MSI: Factor out pci_get_msi_cap() interface Alexander Gordeev
2013-09-17 14:30 ` Michael Ellerman
2013-09-18 9:48 ` Alexander Gordeev
2013-09-18 14:22 ` Tejun Heo
2013-09-18 16:50 ` Alexander Gordeev
2013-09-20 8:24 ` Alexander Gordeev
2013-09-20 12:27 ` Tejun Heo
2013-09-25 18:02 ` Bjorn Helgaas
2013-09-25 20:58 ` Alexander Gordeev
2013-09-25 21:00 ` Tejun Heo
2013-09-26 7:46 ` Alexander Gordeev
2013-09-26 8:58 ` David Laight
2013-09-26 10:45 ` Alexander Gordeev
2013-09-26 11:34 ` David Laight
2013-09-26 12:13 ` Alexander Gordeev
2013-09-26 13:11 ` Tejun Heo
2013-09-26 14:39 ` Alexander Gordeev [this message]
2013-09-26 14:42 ` Tejun Heo
2013-10-01 7:19 ` Michael Ellerman
2013-09-20 12:26 ` Tejun Heo
2013-10-01 7:26 ` Michael Ellerman
2013-10-01 7:35 ` Michael Ellerman
2013-10-01 11:55 ` Tejun Heo
2013-10-02 2:33 ` Michael Ellerman
2013-10-02 3:23 ` Tejun Heo
2013-09-26 12:32 ` Mark Lord
2013-09-26 13:03 ` Alexander Gordeev
2013-10-02 2:46 ` Mark Lord
2013-10-02 7:26 ` Alexander Gordeev
2013-12-18 18:26 ` Bjorn Helgaas
2013-10-01 7:51 ` Michael Ellerman
2013-10-01 10:35 ` Alexander Gordeev
2013-10-02 2:43 ` Michael Ellerman
2013-10-02 7:10 ` Alexander Gordeev
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