From: Julien Grall <julien@xen.org>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
Xen-devel <xen-devel@lists.xenproject.org>
Cc: "Stefano Stabellini" <sstabellini@kernel.org>,
"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
"Wei Liu" <wl@xen.org>, "Jan Beulich" <JBeulich@suse.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH] xen/list: Remove prefetching
Date: Tue, 14 Jan 2020 20:58:21 +0000 [thread overview]
Message-ID: <47ce51b9-3712-5976-0743-06161b65d3a8@xen.org> (raw)
In-Reply-To: <20200114203545.8897-1-andrew.cooper3@citrix.com>
On 14/01/2020 20:35, Andrew Cooper wrote:
> Xen inherited its list infrastructure from Linux. One area where has fallen
> behind is that of prefetching, which as it turns out is a performance penalty
> in most cases.
>
> Prefetch of NULL on x86 is now widely measured to have glacial performance
> properties, and will unconditionally hit on every hlist use due to the
> termination condition.
>
> Cross-port the following Linux patches:
>
> 75d65a425c (2011) "hlist: remove software prefetching in hlist iterators"
> e66eed651f (2011) "list: remove prefetching from regular list iterators"
> c0d15cc7ee (2013) "linked-list: Remove __list_for_each"
>
> to Xen, which results in the following net diffstat on x86:
>
> add/remove: 0/1 grow/shrink: 27/83 up/down: 576/-1648 (-1072)
>
> (The code additions comes from a few now-inlined functions, and slightly
> different basic block padding.)
>
> No functional change.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Julien Grall <julien@xen.org>
Cheers,
--
Julien Grall
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
next prev parent reply other threads:[~2020-01-14 20:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-14 20:35 [Xen-devel] [PATCH] xen/list: Remove prefetching Andrew Cooper
2020-01-14 20:58 ` Julien Grall [this message]
2020-01-15 10:39 ` Roger Pau Monné
2020-01-15 11:25 ` Andrew Cooper
2020-01-15 11:17 ` Jan Beulich
2020-01-15 12:40 ` Andrew Cooper
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=47ce51b9-3712-5976-0743-06161b65d3a8@xen.org \
--to=julien@xen.org \
--cc=JBeulich@suse.com \
--cc=Volodymyr_Babchuk@epam.com \
--cc=andrew.cooper3@citrix.com \
--cc=roger.pau@citrix.com \
--cc=sstabellini@kernel.org \
--cc=wl@xen.org \
--cc=xen-devel@lists.xenproject.org \
/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.