From: Tim Chen <tim.c.chen@linux.intel.com>
To: Jeff Garzik <jeff@garzik.org>
Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>,
linux-scsi <linux-scsi@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Vasu Dev <vasu.dev@linux.intel.com>,
Andi Kleen <ak@linux.intel.com>,
Matthew Wilcox <willy@linux.intel.com>,
James Bottomley <James.Bottomley@suse.de>,
Mike Christie <michaelc@cs.wisc.edu>,
James Smart <james.smart@emulex.com>,
Andrew Vasquez <andrew.vasquez@qlogic.com>,
FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
Hannes Reinecke <hare@suse.de>, Joe Eykholt <jeykholt@cisco.com>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 0/8] Drop host_lock around LLD SHT->queuecommand() caller
Date: Fri, 17 Sep 2010 12:01:52 -0700 [thread overview]
Message-ID: <1284750112.7280.160.camel@schen9-DESK> (raw)
In-Reply-To: <4C93B2BC.8000404@garzik.org>
On Fri, 2010-09-17 at 14:26 -0400, Jeff Garzik wrote:
>
> But that raises the familiar tale of: using multiple atomics (w/ their
> locked instructions) may cost more than a spinlock.
>
As brought up by James earlier, the scsi_host lock was used in so many
places that getting rid of it here to reduce contention for it will be a
net win, even with the cost of the atomics. And for most LLDs that
don't need the serial number, we can just initialize it to zero for
those and have no need to increment it (thus also avoiding the atomics'
cost).
Tim
prev parent reply other threads:[~2010-09-17 19:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-16 22:35 Nicholas A. Bellinger
2010-09-16 22:39 ` Nicholas A. Bellinger
2010-09-16 23:01 ` Nicholas A. Bellinger
2010-09-16 23:18 ` Nicholas A. Bellinger
2010-09-16 23:26 ` Chetan Loke
2010-09-16 23:28 ` Nicholas A. Bellinger
2010-09-17 1:29 ` Tim Chen
2010-09-17 1:31 ` Nicholas A. Bellinger
2010-09-17 18:26 ` Jeff Garzik
2010-09-17 18:24 ` Nicholas A. Bellinger
2010-09-17 19:01 ` Tim Chen [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1284750112.7280.160.camel@schen9-DESK \
--to=tim.c.chen@linux.intel.com \
--cc=James.Bottomley@suse.de \
--cc=ak@linux.intel.com \
--cc=andrew.vasquez@qlogic.com \
--cc=fujita.tomonori@lab.ntt.co.jp \
--cc=hare@suse.de \
--cc=hch@lst.de \
--cc=james.smart@emulex.com \
--cc=jeff@garzik.org \
--cc=jeykholt@cisco.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=michaelc@cs.wisc.edu \
--cc=nab@linux-iscsi.org \
--cc=vasu.dev@linux.intel.com \
--cc=willy@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®