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From: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
To: "dfaggioli@suse.com" <dfaggioli@suse.com>,
	"jgross@suse.com" <jgross@suse.com>,
	"julien@xen.org" <julien@xen.org>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: "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>,
	"jbeulich@suse.com" <jbeulich@suse.com>,
	"roger.pau@citrix.com" <roger.pau@citrix.com>
Subject: Re: [RFC PATCH v1 1/6] sched: track time spent in IRQ handler
Date: Fri, 12 Jun 2020 22:25:29 +0000	[thread overview]
Message-ID: <9e92fd70d92da18caa9e6345b4ce35b86f88605e.camel@epam.com> (raw)
In-Reply-To: <0fc7034d696bbc601ccf2bd563ef9fb435499eea.camel@suse.com>

Hi Dario,

On Fri, 2020-06-12 at 22:08 +0200, Dario Faggioli wrote:
> On Fri, 2020-06-12 at 13:21 +0100, Julien Grall wrote:
> > On 12/06/2020 12:33, Volodymyr Babchuk wrote:
> > > On Fri, 2020-06-12 at 12:29 +0100, Julien Grall wrote:
> > > > > Basically, this value holds time span between calls to
> > > > > schedule(). This
> > > > > variable gets zeroed out every time scheduler requests for time
> > > > > adjustment value. So, it should not depend on total VM run
> > > > > time.
> > > > This is assuming that the scheduler will be called. With the NULL
> > > > scheduler in place, there is a fair chance this may never be
> > > > called.
> > > > 
> Yeah, this is a good point. I mean, I wouldn't be sure about "never",
> as even there, we'd probably have softirqs, tasklets, etc... And I
> still have to look at these patches in more details to figure out
> properly whether they'd help for this.

Well. I think, it is possible to reset counters when we are switching
to a different scheduler. Just for cases like that.

> But I'd say that, in general, we should depend of the frequency of the
> scheduling events as few as possible. Therefore, using 64 bits from the
> start would be preferrable IMO.

I should done that calculation earlier... So, it appears that 32 bit
counter can count up to 4 mere seconds. It should be enought for normal
flow. But I'm agree with you - 64 bits looks much safer. 

> 
> > > > So I think using a 64-bit value is likely safer.
> Yep.
> 
> > > Well, I wanted to use 64-bit value in the first place. But I got
> > > the
> > > impression that atomic_t supports only 32-bit values. At least,
> > > this is
> > > what I'm seeing in atomic.h
> > > 
> > > Am I wrong?
> > 
> > There is no atomic64_t support in Xen yet. It shouldn't be very 
> > difficult to add support for it if you require them.
> > 
> Cool! That would be much appreciated. :-D
> 

Certainly! :)

I believe, there will be another users for atmic64_t as well.



  reply	other threads:[~2020-06-12 22:25 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 [this message]
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
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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