From: willy@linux.intel.com (Matthew Wilcox)
Subject: [PATCH] NVMe: Remove superfluous cqe_seen
Date: Fri, 23 May 2014 10:55:34 -0400 [thread overview]
Message-ID: <20140523145534.GQ6121@linux.intel.com> (raw)
In-Reply-To: <80B89753B40C5141A3E2D53FE7A2A8A9943A7ADC@NTXBOIMBX02.micron.com>
On Thu, May 22, 2014@12:10:19AM +0000, Sam Bradshaw (sbradshaw) wrote:
> Performance problem, though not very easily measured. At very high iops
> rates, most if not all cqe's are processed via nvme_process_cq() in
> make_request(), leaving nvme_irq() with no work to do. Nevertheless, it
> always writes cqe_seen, which invalidates a very hot cacheline. This
> is somewhat exacerbated when IO submissions originate on a remote node
> relative to the cpu handling the irq.
>
> Perhaps a simpler patch where cqe_seen is only written if set?
Sure, we could do that, although in the scenario you're talking about,
cqe_seen would almost always get written. I think your workload would
perhaps benefit from tuning the interrupt coalescing settings.
next prev parent reply other threads:[~2014-05-23 14:55 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-21 18:14 [PATCH] NVMe: Remove superfluous cqe_seen Sam Bradshaw
2014-05-21 23:17 ` Matthew Wilcox
2014-05-22 0:10 ` Sam Bradshaw (sbradshaw)
2014-05-23 14:55 ` Matthew Wilcox [this message]
2014-06-19 16:59 ` Matthew Wilcox
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=20140523145534.GQ6121@linux.intel.com \
--to=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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.