linux-kernel - Re: [RFC][PATCH 13/16] sched: Add core wide task selection and scheduling.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 10 Apr 2019 16:44:18 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Aaron Lu <aaron.lu@...ux.alibaba.com>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>, mingo@...nel.org,
        tglx@...utronix.de, pjt@...gle.com, torvalds@...ux-foundation.org,
        linux-kernel@...r.kernel.org, subhra.mazumdar@...cle.com,
        fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
        Aubrey Li <aubrey.intel@...il.com>,
        Julien Desfossez <jdesfossez@...italocean.com>
Subject: Re: [RFC][PATCH 13/16] sched: Add core wide task selection and
 scheduling.

On Wed, Apr 10, 2019 at 12:36:33PM +0800, Aaron Lu wrote:
> On Tue, Apr 09, 2019 at 11:09:45AM -0700, Tim Chen wrote:
> > Now that we have accumulated quite a number of different fixes to your orginal
> > posted patches.  Would you like to post a v2 of the core scheduler with the fixes?
> 
> One more question I'm not sure: should a task with cookie=0, i.e. tasks
> that are untagged, be allowed to scheduled on the the same core with
> another tagged task?

That was not meant to be possible.

> The current patch seems to disagree on this, e.g. in pick_task(),
> if max is already chosen but max->core_cookie == 0, then we didn't care
> about cookie and simply use class_pick for the other cpu. This means we
> could schedule two tasks with different cookies(one is zero and the
> other can be tagged).

When core_cookie==0 we shouldn't schedule the other siblings at all.

> But then sched_core_find() only allow idle task to match with any tagged
> tasks(we didn't place untagged tasks to the core tree of course :-).
> 
> Thoughts? Do I understand this correctly? If so, I think we probably
> want to make this clear before v2. I personally feel, we shouldn't allow
> untagged tasks(like kernel threads) to match with tagged tasks.

Agreed, cookie should always match or idle.