xen-devel.lists.xenproject.org archive mirror
 help / color / mirror / Atom feed
From: Dario Faggioli <dario.faggioli@citrix.com>
To: Tianyang Chen <tiche@seas.upenn.edu>, xen-devel@lists.xenproject.org
Cc: george.dunlap@citrix.com, Dagaen Golomb <dgolomb@seas.upenn.edu>,
	Meng Xu <mengxu@cis.upenn.edu>
Subject: Re: [PATCH v11]xen: sched: convert RTDS from time to event driven model
Date: Thu, 17 Mar 2016 19:27:39 +0100	[thread overview]
Message-ID: <1458239259.15374.67.camel@citrix.com> (raw)
In-Reply-To: <1458230814-4317-1-git-send-email-tiche@seas.upenn.edu>


[-- Attachment #1.1: Type: text/plain, Size: 2295 bytes --]

On Thu, 2016-03-17 at 12:06 -0400, Tianyang Chen wrote:
> The current RTDS code has several problems:
>  - the scheduler, although the algorithm is event driven by
>    nature, follows a time driven model (is invoked periodically!),
>    making the code look unnatural;
>  - budget replenishment logic, budget enforcement logic and
> scheduling
>    decisions are mixed and entangled, making the code hard to
> understand;
>  - the various queues of vcpus are scanned various times, making the
>    code inefficient;
> 
> This patch separates budget replenishment and enforcement. It does
> that
> by handling the former with a dedicated timer, and a queue of pending
> replenishment events.
> 
> A replenishment queue has been added to keep track of all vcpus that
> are runnable.
> 
> We also make sure that the main scheduling function is called when a
> scheduling decision is necessary, such as when the currently running
> vcpu runs out of budget.
> 
> Finally, when waking up a vcpu, it is now enough to tickle the
> various
> CPUs appropriately, like all other schedulers also do.
> 
> Signed-off-by: Tianyang Chen <tiche@seas.upenn.edu>
> Signed-off-by: Meng Xu <mengxu@cis.upenn.edu>
> Signed-off-by: Dagaen Golomb <dgolomb@seas.upenn.edu>
>
You seem to have taken care of all my remaining comments to v10, so the
patch is:

Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>

(which you could have put there yourself, as I said. :-))

Thanks for all the good work.

If I can already point you to something else that can be improved
further in this scheduler, _completely_ independently from this, and
hence in a fully new patch (series), can you have a look at whether we
really need set_bit(), test_and_clear(), etc, instead of __set_bit(),
__test_and_clear(), etc.?

I'm asking because I'm under the impression that the latter are enough,
and if that is the case, we should go for them, as they're more
efficient.

Thanks again and Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


[-- Attachment #1.2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 181 bytes --]

[-- Attachment #2: Type: text/plain, Size: 126 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel

  reply	other threads:[~2016-03-17 18:27 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-17 16:06 Tianyang Chen
2016-03-17 18:27 ` Dario Faggioli [this message]
2016-03-17 20:12   ` Chen, Tianyang
2016-03-18  1:45     ` Meng Xu
2016-03-18  4:09 ` Meng Xu
2016-03-18  7:45   ` Jan Beulich
2016-03-18  9:23     ` Dario Faggioli
2016-03-18 14:23       ` Meng Xu
2016-03-18 14:19     ` Meng Xu
2016-03-18  9:24   ` Dario Faggioli
2016-03-18 14:25 ` Meng Xu

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=1458239259.15374.67.camel@citrix.com \
    --to=dario.faggioli@citrix.com \
    --cc=dgolomb@seas.upenn.edu \
    --cc=george.dunlap@citrix.com \
    --cc=mengxu@cis.upenn.edu \
    --cc=tiche@seas.upenn.edu \
    --cc=xen-devel@lists.xenproject.org \
    --subject='Re: [PATCH v11]xen: sched: convert RTDS from time to event driven model' \
    /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

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).