From: Grant Grundler <iod00d@hp.com>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Steve Wise <swise@opengridcomputing.com>,
rdreier@cisco.com, linux-kernel@vger.kernel.org,
openib-general@openib.org, netdev@vger.kernel.org
Subject: Re: [openib-general] [PATCH v3 1/7] AMSO1100 Low Level Driver.
Date: Fri, 23 Jun 2006 10:14:57 -0700 [thread overview]
Message-ID: <20060623171457.GA3610@esmail.cup.hp.com> (raw)
In-Reply-To: <1151071471.3204.12.camel@laptopd505.fenrus.org>
On Fri, Jun 23, 2006 at 04:04:31PM +0200, Arjan van de Ven wrote:
> > I thought the posted write WILL eventually get to adapter memory. Not
> > stall forever cached in a bridge. I'm wrong?
>
> I'm not sure there is a theoretical upper bound....
I'm not aware of one either since MMIO writes can travel
across many other chips that are not constrained by
PCI ordering rules (I'm thinking of SGI Altix...)
> (and if it's several msec per bridge, then you have a lot of latency
> anyway)
That's what my original concern was when I saw you point this out.
But MMIO reads here would be expensive and many drivers tolerate
this latency in exchange for avoiding the MMIO read in the
performance path.
grant
next prev parent reply other threads:[~2006-06-23 17:13 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-06-20 20:30 [PATCH v3 0/7][RFC] Ammasso 1100 iWARP Driver Steve Wise
2006-06-20 20:30 ` [PATCH v3 1/7] AMSO1100 Low Level Driver Steve Wise
2006-06-20 20:43 ` Arjan van de Ven
2006-06-21 16:32 ` Steve Wise
2006-06-21 17:13 ` Arjan van de Ven
2006-06-21 18:47 ` Steve Wise
2006-06-21 17:37 ` [openib-general] " Grant Grundler
2006-06-23 13:44 ` Steve Wise
2006-06-23 13:48 ` Arjan van de Ven
2006-06-23 13:56 ` Steve Wise
2006-06-23 14:04 ` Arjan van de Ven
2006-06-23 17:14 ` Grant Grundler [this message]
2006-06-23 18:02 ` Michael Krause
2006-06-20 20:31 ` [PATCH v3 2/7] AMSO1100 WR / Event Definitions Steve Wise
2006-06-20 20:31 ` [PATCH v3 3/7] AMSO1100 OpenFabrics Provider Steve Wise
2006-06-20 20:31 ` [PATCH v3 4/7] AMSO1100 Memory Management Steve Wise
2006-06-20 20:31 ` [PATCH v3 5/7] AMSO1100 Message Queues Steve Wise
2006-06-20 20:31 ` [PATCH v3 6/7] AMSO1100: Privileged Verbs Queues Steve Wise
2006-06-20 20:31 ` [PATCH v3 7/7] AMSO1100 Makefiles and Kconfig changes Steve Wise
2006-06-20 21:00 ` [PATCH v3 2/7] AMSO1100 WR / Event Definitions Steve Wise
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