From: Peter Zijlstra <peterz@infradead.org>
To: Chris Hyser <chris.hyser@oracle.com>
Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>,
Nishanth Aravamudan <naravamudan@digitalocean.com>,
Julien Desfossez <jdesfossez@digitalocean.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Vineeth Pillai <viremana@linux.microsoft.com>,
Aaron Lu <aaron.lwe@gmail.com>,
Aubrey Li <aubrey.intel@gmail.com>,
tglx@linutronix.de, linux-kernel@vger.kernel.org,
mingo@kernel.org, torvalds@linux-foundation.org,
fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com,
Phil Auld <pauld@redhat.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Mel Gorman <mgorman@techsingularity.net>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
vineeth@bitbyteword.org, Chen Yu <yu.c.chen@intel.com>,
Christian Brauner <christian.brauner@ubuntu.com>,
Agata Gruza <agata.gruza@intel.com>,
Antonio Gomez Iglesias <antonio.gomez.iglesias@intel.com>,
graf@amazon.com, konrad.wilk@oracle.com, dfaggioli@suse.com,
pjt@google.com, rostedt@goodmis.org, derkling@google.com,
benbjiang@tencent.com,
Alexandre Chartre <alexandre.chartre@oracle.com>,
James.Bottomley@hansenpartnership.com, OWeisse@umich.edu,
Dhaval Giani <dhaval.giani@oracle.com>,
Junaid Shahid <junaids@google.com>,
jsbarnes@google.com, Ben Segall <bsegall@google.com>,
Josh Don <joshdon@google.com>, Hao Luo <haoluo@google.com>,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH v10 2/5] sched: CGroup tagging interface for core scheduling
Date: Fri, 5 Feb 2021 11:43:03 +0100 [thread overview]
Message-ID: <YB0hN5XG5dB0xiBh@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <94bb9424-008e-6d3c-dff6-a1329c16551f@oracle.com>
On Thu, Feb 04, 2021 at 03:52:55PM -0500, Chris Hyser wrote:
> A second complication was a decision that new processes (not threads) do not
> inherit their parents cookie. Thus forking is also not a means to share a
> cookie. Basically with a "from-only" interface, the new task would need to
> be modified to call prctl() itself. From-only also does not allow for
> setting a cookie on an unmodified already running task. This can be fixed by
> providing both a "to" and "from" sharing interface that allows helper
> programs to construct arbitrary configurations from unmodified programs.
Do we really want to inhibit on fork() or would exec() be a better
place? What about those applications that use fork() based workers?
> > Also, how do I set a unique cookie on myself with this interface?
>
> The v10 patch still uses the overloaded v9 mechanism (which as mentioned
> above is if two tasks w/o cookies share a cookie they get a new shared
> unique cookie). Yes, that is clearly an inconsistency and kludgy. The
> mechanism is documented in the docs, but clearly not obvious from the
I've not seen a document so far (also, I'm not one to actually read
documentation, much preferring comments and Changelogs).
> So based on the above, how about we add a "create" to pair with "clear" and
> call it "create" vs "set" since we are creating a unique opaque cookie
> versus setting a particular value. And as mentioned, because one can't
> specify a cookie directly but only thru sharing relationships, we need both
> "to" and "from" to make it completely usable.
>
> So we end up with something like this:
> PR_SCHED_CORE_CREATE -- give yourself a unique cookie
> PR_SCHED_CORE_CLEAR -- clear your core sched cookie
> PR_SCHED_CORE_SHARE_FROM <src_task> -- get their cookie for you
> PR_SCHED_CORE_SHARE_TO <dest_task> -- push your cookie to them
I'm still wondering why we need _FROM/_TO. What exactly will we miss
with just _SHARE <pid>?
current arg_task
<none> <none> -EDAFT
<none> <cookie> current gets cookie
<cookie> <none> arg_task gets cookie
<cookie> <cookie> -EDAFTER
(I have a suspicion, but I want to see it spelled out).
Also, do we wants this interface to be able to work on processes? Things
like fcntl(F_SETOWN_EX) allow you to specify a PID type.
> An additional question is should the inheritability of a process' cookie be
> configurable? The current code gives the child process their own unique
> cookie if the parent had a cookie. That is useful in some cases, but many
> other configurations could be made much easier with inheritance.
What was the argument for not following the traditional fork() semantics
and inheriting everything?
next prev parent reply other threads:[~2021-02-05 10:48 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-23 1:16 [PATCH v10 0/5] Core scheduling remaining patches Joel Fernandes (Google)
2021-01-23 1:17 ` [PATCH v10 1/5] sched: migration changes for core scheduling Joel Fernandes (Google)
2021-01-23 1:17 ` [PATCH v10 2/5] sched: CGroup tagging interface " Joel Fernandes (Google)
2021-02-03 16:51 ` Peter Zijlstra
2021-02-04 13:59 ` Peter Zijlstra
2021-02-05 16:42 ` Joel Fernandes
2021-02-04 13:54 ` Peter Zijlstra
2021-02-05 3:45 ` Josh Don
2021-02-04 13:57 ` Peter Zijlstra
2021-02-04 20:52 ` Chris Hyser
2021-02-05 10:43 ` Peter Zijlstra [this message]
2021-02-05 22:19 ` Chris Hyser
2021-02-04 14:01 ` Peter Zijlstra
2021-02-05 3:55 ` Josh Don
2021-02-04 14:35 ` Peter Zijlstra
2021-02-05 4:07 ` Josh Don
2021-02-04 14:52 ` Peter Zijlstra
2021-02-05 16:37 ` Joel Fernandes
2021-02-05 11:41 ` Peter Zijlstra
2021-02-05 11:52 ` Peter Zijlstra
2021-02-06 1:15 ` Josh Don
2021-02-05 12:00 ` Peter Zijlstra
2021-02-23 4:00 ` Chris Hyser
2021-02-23 9:05 ` Peter Zijlstra
2021-02-23 19:25 ` Chris Hyser
2021-02-24 5:15 ` Josh Don
2021-02-24 13:02 ` Chris Hyser
2021-02-24 13:52 ` chris hyser
2021-02-24 15:47 ` chris hyser
2021-02-26 20:07 ` Chris Hyser
2021-03-01 21:01 ` Josh Don
2021-01-23 1:17 ` [PATCH v10 3/5] kselftest: Add tests for core-sched interface Joel Fernandes (Google)
2021-01-23 1:17 ` [PATCH v10 4/5] Documentation: Add core scheduling documentation Joel Fernandes (Google)
2021-01-23 1:17 ` [PATCH v10 5/5] sched: Debug bits Joel Fernandes (Google)
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