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From: Meng Xu <xumengpanda@gmail.com>
To: "Chen, Tianyang" <tiche@seas.upenn.edu>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	Dario Faggioli <dario.faggioli@citrix.com>,
	George Dunlap <george.dunlap@citrix.com>,
	Dagaen Golomb <dgolomb@seas.upenn.edu>
Subject: Re: [PATCH v11]xen: sched: convert RTDS from time to event driven model
Date: Thu, 17 Mar 2016 21:45:15 -0400	[thread overview]
Message-ID: <CAENZ-+nYibena33R4RXNT_Mg_dE8TiYJ5Mnz_RLQ9o2wjZ7K1g@mail.gmail.com> (raw)
In-Reply-To: <56EB0F96.8090905@seas.upenn.edu>

>> 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.
> Sure. __set_bit() and __test_and_clear() are not atomic and can be
> reordered. They need to be protected by locks. So, it looks like where RTDS
> is using them already have spin_locks in place and re-ordering inside the
> critical region doesn't really mess anything up.
> rt_schedule() sets: __RTDS_scheduled, __RTDS_delay_runq_add
> burn_budget() sets: __RTDS_depleted
> rt_wake() sets: __RTDS_delay_runq_add
> rt_vcpu_sleep() clears: __RTDS_delayed_runq_add
> rt_context_saved() clears: __RTDS_scheduled, __RTDS_delayed_runq_add
> repl_timer_handler() clears: __RTDS_depleted
> burn_budget() is inside of rt_schedule() but they are using different flags
> of different vcpus. So it's enough to just use __set_bit(), __clear_bit()
> and __test_and_clear().
> I'm assuming the new patch should be based on the last patch I sent? Because
> replenishment handler is not presented in the old RTDS code?

Yes. You can work on the latest staging commit point and later rebase it.

BTW, I'm testing the patch tonight and will send out my Reviewed-by
tag once I tested it...



Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania

Xen-devel mailing list

  reply	other threads:[~2016-03-18  1:45 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
2016-03-17 20:12   ` Chen, Tianyang
2016-03-18  1:45     ` Meng Xu [this message]
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

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