Re: Kernel thread scheduling

[Aruna Hewapathirane <aruna.hewapathirane@xxxxxxxxx>]

>> I'm trying to find rb_node's structure and I can't find it with ctags or
>> in the http://lxr.linux.no website.

Please use this: Linux 2.6.11 and later

At the top right there is a text box please type what your searching for, in this rb_node. It will show you on the right the search results.

The Structure is defined here: include/linux/rbtree.h, line 35

and here it is in case you have difficulties:

struct rb_node {
        unsigned long  __rb_parent_color;
        struct rb_node *rb_right;
        struct rb_node *rb_left;
} __attribute__((aligned(sizeof(long))));
    /* The alignment might seem pointless, but allegedly CRIS needs it */

Thank's - Aruna

Ruben

On Thu, Apr 09, 2015 at 10:52:03PM -0400, nick wrote:
>
>
> On 2015-04-09 10:12 PM, Ruben Safir wrote:
> > On 04/09/2015 10:00 PM, nick wrote:
> >>
> >>
> >> On 2015-04-09 09:51 PM, Ruben Safir wrote:
> >>>
> >>> It is passover so I've read over much of this text, but I have to say
> >>> that in general, I'm way ahead of this book.  Although I have limited
> >>> knowledge of Kernel technology in the specific, the C code, data
> >>> structs, and programming concepts are spoon feed in this text and its
> >>> wasting too much time with words that are more easily explained with
> >>> coding examples and UML charts.  I don't need a chapter explaining how
> >>> to use ps and the basis of Unix architecture.  This text is targeted to
> >>> a different audience, and FWIW, I'm not certain it does a good job of
> >>> that either.  The guys who write these texts fall in love with their own
> >>> voices.  I know, I've suffered this disease myself when I've written
> >>> tech articles and books.
> >>>
> >>> I can''t recommend this book to anyone.  Anyone who doesn't understand
> >>> the basics of I/O processer blocks is not going to understand
> >>>
> >>> static void update_curr(struct cfs_rq *cfs_rq)
> >>>
> >>>
> >>> and OTOH void update_curr(struct cfs_rq *cfs_rq) is not explained well
> >>> enough for coders unfamiliar with the kernel data structs of which BTW
> >>> struct cfs_rq is not one defined in the text.
> >>>
> >>> :(
> >>>
> >>> I'm looking for something more like this, but flushed out more as a textbook
> >>>
> >>> http://www.ibm.com/developerworks/library/l-completely-fair-scheduler/index.html,
> >>> and some mentoring, I hope.
> >>>
> >>>
> >>> Ruben
> >>>
>
> >> Ruben,
> >> The book is for an intro to the kernel not a complete walk through of each subsystem.
> >> If that is the case,why not read the subsystem code and docs in the kernel. I am a
> >> novice myself in terms of patch and coding experience but will be glad to explain the
> >> code as I have read lots of it.
> >
> >
> > Thank you nick.  Yes, I downloaded the entire source from Kernel.org and
> > it is sitting on both my laptop and in virtual machines where I have
> > already compiled some stuff and not broken my VMs yets :)
> >
> > I'm looking over  /home/ruben/linux-3.19.3/Documentation/scheduler
> > [ruben@stat13 scheduler]$ ls
> >
> > 00-INDEX   sched-deadline.txt     sched-rt-group.txt
> > media=legal -o sides=two-sided-long-edg  sched-design-CFS.txt
> > sched-stats.txt sched-arch.txt sched-domains.txt
> > sched-bwc.txt   sched-nice-design.txt
> >
> >
> > I also see in the code there is significant documentation.
> >
> > Right now I am trying to figure out what is the relationship between
> > struct sched_entity and
> > struct cfs_rq and
> > struct rq_of
> >
> > why do we have both??
> >
> The way that these structures  are related is sched_enity is the entity for the task's scheduling
> information or the task_struct of the a excuting process to be exact. Furthermore  cfs_rq is the
> runquenue on which the task is running or selected to run on by schedule,the main scheduling function
> of the kernel. Finally here is the function definition for rq_of to answer your question,
> static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
> {
>       return cfs_rq->rq;
> }
> Before asking questions again like this please look into either using lxr or ctags
> to navigate the kernel tree for answers as can be faster then waiting for me or
> someone else to respond.
> Thanks,
> Nick
> > there is a cast in update_curr
> > u64 now = rq_of(cfs_rq)->clock;
> >
> > or is rq_of a function that returns a pointer is a struct that I missed?
> >
> >
> >
> >
> >
> >> Nick
> >>> On 03/22/2015 08:35 PM, nick wrote:
> >>>>
> >>>>
> >>>> On 2015-03-22 08:05 PM, Ruben Safir wrote:
> >>>>> On 03/22/2015 07:30 PM, nick wrote:
> >>>>>> I would recommend reading Chapters 3 and  4 of Linux Kernel Development by Robert Love
> >>>>>> as when I was learning the scheduler and process management
> >>>>>
> >>>>>
> >>>>> how much has the scheduler changed since then.  It was completely
> >>>>> overhauled when the CFS was created
> >>>>>
> >>>>>
> >>>>>
> >>>> The 3rd edition of this book was written after CFS was in the kernel so the chapters
> >>>> are pretty up to date.
> >>>> Nick
> >>>>> _______________________________________________
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> >>>>>
> >>>>
> >>>> _______________________________________________
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> >>>>
> >>>> .
> >>>>
> >>>
> >>>
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> >>>
> >>
> >>
> >
>
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