From: Tejun Heo <tj@kernel.org>
To: Alexander Gordeev <agordeev@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org
Subject: Re: [PATCH RESEND v3 5/6] AHCI: Optimize single IRQ interrupt processing
Date: Sun, 5 Oct 2014 12:16:46 -0400 [thread overview]
Message-ID: <20141005161646.GB22223@mtj.dyndns.org> (raw)
In-Reply-To: <20141005022311.GD8549@htj.dyndns.org>
A bit of addition.
On Sat, Oct 04, 2014 at 10:23:11PM -0400, Tejun Heo wrote:
> Hmmm.... so, AFAICS, there's no real pros or cons of going either way,
> right? The only thing which could be different is possibly slightly
> lower latency in servicing other IRQs or RT tasks on the same CPU but
> given that the ahci IRQ handler already doesn't do anything which
> takes time, I'm doubtful whether that'd be anything measureable.
>
> I just don't get why ahci bothers with threaded irq, MMSI or not.
I think the thing which bothers me is that due to softirq we end up
bouncing the context twice. IRQ schedules threaded IRQ handler after
doing minimal amount of work. The threaded IRQ handler gets scheduled
and again it doesn't do much but basically just schedules block
softirq to actually run completions which is the heavier part.
Apparently this doesn't seem to hurt measureably but it's just weird.
Why are we bouncing the context twice?
Thanks.
--
tejun
next prev parent reply other threads:[~2014-10-05 16:16 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-21 13:19 [PATCH RESEND v3 0/6] AHCI: Optimize interrupt processing Alexander Gordeev
2014-09-21 13:19 ` [PATCH RESEND v3 1/6] AHCI: Cleanup checking of multiple MSIs/SLM modes Alexander Gordeev
2014-09-23 20:18 ` Tejun Heo
2014-09-21 13:19 ` [PATCH RESEND v3 2/6] AHCI: Move host activation code into ahci_host_activate() Alexander Gordeev
2014-09-23 20:22 ` Tejun Heo
2014-09-23 20:55 ` Tejun Heo
2014-09-21 13:19 ` [PATCH RESEND v3 3/6] AHCI: Make few function names more descriptive Alexander Gordeev
2014-09-23 20:22 ` Tejun Heo
2014-09-21 13:19 ` [PATCH RESEND v3 4/6] AHCI: Get rid of redundant arg to ahci_handle_port_interrupt() Alexander Gordeev
2014-09-21 13:19 ` [PATCH RESEND v3 5/6] AHCI: Optimize single IRQ interrupt processing Alexander Gordeev
2014-09-23 20:57 ` Tejun Heo
2014-09-24 10:42 ` Alexander Gordeev
2014-09-24 13:04 ` Tejun Heo
2014-09-24 13:27 ` Chuck Ebbert
2014-09-24 13:36 ` Tejun Heo
2014-09-24 14:08 ` Alexander Gordeev
2014-09-24 14:39 ` Tejun Heo
2014-09-24 14:59 ` Alexander Gordeev
2014-09-25 3:27 ` Tejun Heo
2014-10-01 15:31 ` Alexander Gordeev
2014-10-01 15:39 ` Alexander Gordeev
2014-10-05 2:23 ` Tejun Heo
2014-10-05 16:16 ` Tejun Heo [this message]
2014-10-06 7:27 ` Alexander Gordeev
2014-10-06 12:58 ` Tejun Heo
2014-10-06 13:24 ` Alexander Gordeev
2014-10-06 14:54 ` Tejun Heo
2014-09-25 3:00 ` Elliott, Robert (Server Storage)
2014-09-21 13:19 ` [PATCH RESEND v3 6/6] AHCI: Do not read HOST_IRQ_STAT reg in multi-MSI mode Alexander Gordeev
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