From: Meng Xu <xumengpanda@gmail.com>
To: Chong Li <lichong659@gmail.com>
Cc: Chong Li <chong.li@wustl.edu>, Wei Liu <wei.liu2@citrix.com>,
Sisu Xi <xisisu@gmail.com>,
GeorgeDunlap <george.dunlap@eu.citrix.com>,
Dario Faggioli <dario.faggioli@citrix.com>,
xen-devel <xen-devel@lists.xen.org>,
Jan Beulich <JBeulich@suse.com>,
Dagaen Golomb <dgolomb@seas.upenn.edu>
Subject: Re: [PATCH v6 for Xen 4.7 1/4] xen: enable per-VCPU parameter settings for RTDS scheduler
Date: Tue, 15 Mar 2016 23:43:37 -0400 [thread overview]
Message-ID: <CAENZ-+n+_Zdqga9meESNc7kCkD9Z-WB3Q3h+5Bg7edg=J4p5Pw@mail.gmail.com> (raw)
In-Reply-To: <CAGHO-irERtgcAcEomjHCOYezjzT0R_FsDfSz3i2Ofcjj8Fq+aA@mail.gmail.com>
On Tue, Mar 15, 2016 at 11:32 PM, Chong Li <lichong659@gmail.com> wrote:
> On Tue, Mar 15, 2016 at 10:14 PM, Meng Xu <mengxu@cis.upenn.edu> wrote:
>> On Tue, Mar 15, 2016 at 1:22 PM, Chong Li <lichong659@gmail.com> wrote:
>>> On Tue, Mar 15, 2016 at 11:41 AM, Dario Faggioli
>>> <dario.faggioli@citrix.com> wrote:
>>>> On Tue, 2016-03-15 at 11:22 -0500, Chong Li wrote:
>>>>> On Mon, Mar 14, 2016 at 5:05 AM, Dario Faggioli
>>>>> <dario.faggioli@citrix.com> wrote:
>>>>> >
>>>>
>>>> We said 'once' and then 'once per domain', but something I'd be fine
>>>> with (coupled with keeping G_WARNING) would be 'once per operation'.
>>>> Basically, if a domain has 128 vcpus, and an hypercall tries to set all
>>>> of them to period=100, budget=50, we just print the warning once. Then,
>>>> if after a while the sysadmin tries the same again, we again just log
>>>> once, etc.
>>>>
>>>> Doing this seems much easier, as the 'warned' flag could just be a
>>>> local variable of the hypercall implementation. I'm quite sure that
>>>> would work if there is not any continuation/re-issueing mechanism in
>>>> the hypercall in question. BUT in our case there is, so things may be
>>>> more complicated... :-/
>>>>
>>>> Had you thought about a solution like this already? If no, can you see
>>>> whether there is a nice and easy way to make something like what I just
>>>> described above to work in our case?
>>>>
>>> How about:
>>>
>>> We create a global variable in sched_rt.c:
>>> /* This variable holds its value through hyerpcall re-issueing.
>>> * When finding vcpu settings with too low budget or period (e.g,
>>> 100 us), we print a warning
>>> * and set this variable "true". No more warnings are printed
>>> until this variable
>>> * becomes false.
>>> */
>>> static bool warned;
>>> Initialize it as "false" in rt_init().
>>> In your example,
>>> we "warned = true" when we find the first vcpu has budget less than
>>> 100 us. Outside
>>> of the while loop, we do:
>>> if ( index == op->u.v.nr_vcpus ) /* no more hypercall re-issueing */
>>> warned = false;
>>>
>> Hi Chong,
>>
>> I don't think creating a global variable just for the warning thing is
>> a better idea. Even if we do want such a variable, it should only
>> occur in rt_dom_cntl() function, since it is only used in
>> rt_dom_cntl().
>> Global variable should be used "globally", isn't it. ;-)
>>
> You're right.
>
> If we define
>
> static bool warned;
>
> at the beginning of rt_dom_cntl(), do we need to initialize it? If without
> initialization, I think its default value is "false", which is just
> what we need.
>
We need initializing any variable we are going to use, of course. We
should not reply on the compiler to give an initialized value. :-)
Meng
--
-----------
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/
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next prev parent reply other threads:[~2016-03-16 3:43 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-06 17:55 [PATCH v6 for Xen 4.7 0/4] Enable per-VCPU parameter settings for RTDS scheduler Chong Li
2016-03-06 17:55 ` [PATCH v6 for Xen 4.7 1/4] xen: enable " Chong Li
2016-03-07 12:59 ` Jan Beulich
2016-03-07 16:28 ` Chong Li
2016-03-07 16:40 ` Jan Beulich
2016-03-07 17:53 ` Dario Faggioli
2016-03-07 22:16 ` Chong Li
2016-03-08 9:10 ` Jan Beulich
2016-03-08 10:34 ` Dario Faggioli
2016-03-08 11:47 ` Jan Beulich
2016-03-08 19:09 ` Wei Liu
2016-03-09 16:10 ` Dario Faggioli
2016-03-09 16:38 ` Jan Beulich
2016-03-13 17:05 ` Chong Li
2016-03-14 8:37 ` Jan Beulich
2016-03-14 9:10 ` Dario Faggioli
2016-03-14 9:15 ` Jan Beulich
2016-03-14 10:05 ` Dario Faggioli
2016-03-15 16:22 ` Chong Li
2016-03-15 16:41 ` Dario Faggioli
2016-03-15 17:22 ` Chong Li
2016-03-16 3:14 ` Meng Xu
2016-03-16 3:32 ` Chong Li
2016-03-16 3:43 ` Meng Xu [this message]
2016-03-16 8:23 ` Dario Faggioli
2016-03-16 14:37 ` Meng Xu
2016-03-16 14:46 ` Chong Li
2016-03-16 14:53 ` Dario Faggioli
2016-03-16 14:46 ` Chong Li
2016-03-16 14:54 ` Dario Faggioli
2016-03-16 10:48 ` Jan Beulich
2016-03-10 22:35 ` Chong Li
2016-03-10 22:50 ` Wei Liu
2016-03-14 9:07 ` Dario Faggioli
2016-03-06 17:55 ` [PATCH v6 for Xen 4.7 2/4] libxc: " Chong Li
2016-03-08 19:09 ` Wei Liu
2016-03-08 19:32 ` Chong Li
2016-03-08 19:36 ` Wei Liu
2016-03-06 17:55 ` [PATCH v6 for Xen 4.7 3/4] libxl: " Chong Li
2016-03-08 19:12 ` Wei Liu
2016-03-09 0:38 ` Chong Li
2016-03-09 14:01 ` Wei Liu
2016-03-09 17:28 ` Dario Faggioli
2016-03-09 21:57 ` Chong Li
2016-03-09 17:09 ` Dario Faggioli
2016-03-09 17:28 ` Dario Faggioli
2016-03-06 17:55 ` [PATCH v6 for Xen 4.7 4/4] xl: " Chong Li
2016-03-08 19:12 ` Wei Liu
2016-03-08 21:24 ` Chong Li
2016-03-09 14:01 ` Wei Liu
2016-03-09 14:09 ` Wei Liu
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