From: Jesse Barnes <jbarnes@virtuousgeek.org>
To: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>,
Matthew Wilcox <matthew@wil.cx>,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
linux-rt-users@vger.kernel.org
Subject: Re: [PATCH] msi: skip calling pci_find_capability from msi_set_mask_bits
Date: Mon, 19 May 2008 13:11:45 -0700 [thread overview]
Message-ID: <200805191311.46162.jbarnes@virtuousgeek.org> (raw)
In-Reply-To: <48310691.9050706@jp.fujitsu.com>
On Sunday, May 18, 2008 9:48 pm Hidetoshi Seto wrote:
> Jesse Barnes wrote:
> > Since we know MSI is a problem, let's just go with fixing that for now.
> > If we find that other caps are also causing problems we can revisit
> > caching all of them; the patch is simple enough.
>
> Humm...
> I suppose it can be more simple. How about this patch?
>
> > everytime handle_edge_irq is called it needs to mask and unmask MSI, and
> > that leads to a series of very expensive calls to pci_find_capability
>
> The position of MSI capability is already cached in the msi_desc when
> we enter the msi_set_mask_bits(). Use it instead.
>
> Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Yeah, this looks really nice. It should also fix Arnaldo's latency problem,
and really looks like a bug fix for the MSI code more than anything.
Arnaldo, can you take a look & test and ack/nack?
Thanks,
Jesse
next prev parent reply other threads:[~2008-05-19 20:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-15 16:04 [PATCH][PCI]: Introduce pci_find_capability_cached and make MSI use it Arnaldo Carvalho de Melo
2008-05-15 17:02 ` Arnaldo Carvalho de Melo
2008-05-15 17:04 ` Matthew Wilcox
2008-05-15 17:10 ` Arnaldo Carvalho de Melo
2008-05-16 17:44 ` Jesse Barnes
2008-05-16 18:33 ` Arnaldo Carvalho de Melo
2008-05-16 19:01 ` Jesse Barnes
2008-05-16 19:10 ` Arnaldo Carvalho de Melo
2008-05-19 4:48 ` [PATCH] msi: skip calling pci_find_capability from msi_set_mask_bits Hidetoshi Seto
2008-05-19 20:11 ` Jesse Barnes [this message]
2008-05-19 20:26 ` Arnaldo Carvalho de Melo
2008-05-20 19:56 ` Arnaldo Carvalho de Melo
2008-05-20 20:06 ` Jesse Barnes
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