From: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
To: Julien Grall <julien.grall.oss@gmail.com>
Cc: "jgross@suse.com" <jgross@suse.com>,
"sstabellini@kernel.org" <sstabellini@kernel.org>,
"wl@xen.org" <wl@xen.org>,
"andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>,
"ian.jackson@eu.citrix.com" <ian.jackson@eu.citrix.com>,
"george.dunlap@citrix.com" <george.dunlap@citrix.com>,
"dfaggioli@suse.com" <dfaggioli@suse.com>,
"jbeulich@suse.com" <jbeulich@suse.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: [RFC PATCH v1 4/6] xentop: collect IRQ and HYP time statistics.
Date: Thu, 18 Jun 2020 23:35:02 +0000 [thread overview]
Message-ID: <87wo440wyi.fsf@epam.com> (raw)
In-Reply-To: <CAJ=z9a1h1RN8EAkxZ6AY-Xw_Dcx5f80XP+Pj4RwR8PensaBTLQ@mail.gmail.com>
Hi Julien,
Julien Grall writes:
> On Thu, 18 Jun 2020 at 21:24, Volodymyr Babchuk
> <Volodymyr_Babchuk@epam.com> wrote:
>>
>>
>> Hi Julien,
>>
>> Julien Grall writes:
>>
>> > Hi Volodymyr,
>> >
>> > On 12/06/2020 12:44, Volodymyr Babchuk wrote:
>> >>
>> >> On Fri, 2020-06-12 at 06:57 +0200, Jürgen Groß wrote:
>> >>> On 12.06.20 02:22, Volodymyr Babchuk wrote:
>> >>>> As scheduler code now collects time spent in IRQ handlers and in
>> >>>> do_softirq(), we can present those values to userspace tools like
>> >>>> xentop, so system administrator can see how system behaves.
>> >>>>
>> >>>> We are updating counters only in sched_get_time_correction() function
>> >>>> to minimize number of taken spinlocks. As atomic_t is 32 bit wide, it
>> >>>> is not enough to store time with nanosecond precision. So we need to
>> >>>> use 64 bit variables and protect them with spinlock.
>> >>>>
>> >>>> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
>> >>>> ---
>> >>>> xen/common/sched/core.c | 17 +++++++++++++++++
>> >>>> xen/common/sysctl.c | 1 +
>> >>>> xen/include/public/sysctl.h | 4 +++-
>> >>>> xen/include/xen/sched.h | 2 ++
>> >>>> 4 files changed, 23 insertions(+), 1 deletion(-)
>> >>>>
>> >>>> diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
>> >>>> index a7294ff5c3..ee6b1d9161 100644
>> >>>> --- a/xen/common/sched/core.c
>> >>>> +++ b/xen/common/sched/core.c
>> >>>> @@ -95,6 +95,10 @@ static struct scheduler __read_mostly ops;
>> >>>> static bool scheduler_active;
>> >>>> +static DEFINE_SPINLOCK(sched_stat_lock);
>> >>>> +s_time_t sched_stat_irq_time;
>> >>>> +s_time_t sched_stat_hyp_time;
>> >>>> +
>> >>>> static void sched_set_affinity(
>> >>>> struct sched_unit *unit, const cpumask_t *hard, const cpumask_t *soft);
>> >>>> @@ -994,9 +998,22 @@ s_time_t sched_get_time_correction(struct
>> >>>> sched_unit *u)
>> >>>> break;
>> >>>> }
>> >>>> + spin_lock_irqsave(&sched_stat_lock, flags);
>> >>>> + sched_stat_irq_time += irq;
>> >>>> + sched_stat_hyp_time += hyp;
>> >>>> + spin_unlock_irqrestore(&sched_stat_lock, flags);
>> >>>
>> >>> Please don't use a lock. Just use add_sized() instead which will add
>> >>> atomically.
>> >>
>> >> Looks like arm does not support 64 bit variables. >
>> >> Julien, I believe, this is armv7 limitation? Should armv8 work with 64-
>> >> bit atomics?
>> >
>> > 64-bit atomics can work on both Armv7 and Armv8 :). It just haven't
>> > been plumbed yet.
>> >
>> > I am happy to write a patch if you need atomic64_t or even a 64-bit
>> > add_sized().
>>
>> Looks like I'll need this patch. So, if you still have time, it will be
>> great, if you'll write it.
>
> I offered help for either the atomic64_t or the add_sized(). Can you
> confirm which one you need?
Yes, sorry. I had atomic64_t in mind.
--
Volodymyr Babchuk at EPAM
next prev parent reply other threads:[~2020-06-18 23:35 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-12 0:22 [RFC PATCH v1 0/6] Fair scheduling Volodymyr Babchuk
2020-06-12 0:22 ` [RFC PATCH v1 2/6] sched: track time spent in hypervisor tasks Volodymyr Babchuk
2020-06-12 4:43 ` Jürgen Groß
2020-06-12 11:30 ` Volodymyr Babchuk
2020-06-12 11:40 ` Jürgen Groß
2020-09-24 18:08 ` Volodymyr Babchuk
2020-09-25 17:22 ` Dario Faggioli
2020-09-25 20:21 ` Volodymyr Babchuk
2020-09-25 21:42 ` Dario Faggioli
2020-06-16 10:10 ` Jan Beulich
2020-06-18 2:50 ` Volodymyr Babchuk
2020-06-18 6:34 ` Jan Beulich
2020-06-12 0:22 ` [RFC PATCH v1 1/6] sched: track time spent in IRQ handler Volodymyr Babchuk
2020-06-12 4:36 ` Jürgen Groß
2020-06-12 11:26 ` Volodymyr Babchuk
2020-06-12 11:29 ` Julien Grall
2020-06-12 11:33 ` Volodymyr Babchuk
2020-06-12 12:21 ` Julien Grall
2020-06-12 20:08 ` Dario Faggioli
2020-06-12 22:25 ` Volodymyr Babchuk
2020-06-12 22:54 ` Julien Grall
2020-06-16 10:06 ` Jan Beulich
2020-06-12 0:22 ` [RFC PATCH v1 3/6] sched, credit2: improve scheduler fairness Volodymyr Babchuk
2020-06-12 4:51 ` Jürgen Groß
2020-06-12 11:38 ` Volodymyr Babchuk
2020-06-12 0:22 ` [RFC PATCH v1 5/6] tools: xentop: show time spent in IRQ and HYP states Volodymyr Babchuk
2020-06-12 0:22 ` [RFC PATCH v1 6/6] trace: add fair scheduling trace events Volodymyr Babchuk
2020-06-12 0:22 ` [RFC PATCH v1 4/6] xentop: collect IRQ and HYP time statistics Volodymyr Babchuk
2020-06-12 4:57 ` Jürgen Groß
2020-06-12 11:44 ` Volodymyr Babchuk
2020-06-12 12:45 ` Julien Grall
2020-06-12 22:16 ` Volodymyr Babchuk
2020-06-18 20:24 ` Volodymyr Babchuk
2020-06-18 20:34 ` Julien Grall
2020-06-18 23:35 ` Volodymyr Babchuk [this message]
2020-06-12 12:29 ` Julien Grall
2020-06-12 12:41 ` Jürgen Groß
2020-06-12 15:29 ` Dario Faggioli
2020-06-12 22:27 ` Volodymyr Babchuk
2020-06-13 6:22 ` Jürgen Groß
2020-06-18 2:58 ` Volodymyr Babchuk
2020-06-18 15:17 ` Julien Grall
2020-06-18 15:23 ` Jan Beulich
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