[PATCH v5 0/5] Allow schedulers to be selectable through Kconfig

[PATCH v5 0/5] Allow schedulers to be selectable through Kconfig

[Jonathan Creekmore]

Add machinery to allow the schedulers to be individually selectable
through the Kconfig interface. The first patch in the series sets up
the CONFIG_EXPERT Kconfig variable that is only enabled by passing an
environment variable to the build. The second patch in the series sets up
the Kconfig options for the schedulers and places the appropriate CONFIG_
options around the scheduler list. The third, fourth, and fifth patches
rework the scheduler list from being manually curated into a model
where just compiling any schedulers into the hypervisor causes the
scheduler list to be built up.

---
Changed since v4:
 * Removed the ability to configure the credit scheduler. It is always
   compiled in, so there is no need for the defensive check for schedulers
   in the linker (added in v4) and no reason to provide the static inlines
   (added in v3) since credit is always present. 
 * Remove extra size field that was accidentally left in.

Changed since v3:
 * Add defensive check for schedulers in the linker

Changed since v2:
 * Added a predecessor patch that introduces a environment
   variable for the build to enable expert configuration options
   (1/5)
 * Hide the scheduler menu behind the expert option (2/5)
 * Provide static inlines for credit functions that are assumed to be
   present if it is compiled out (2/5)
 * Provide an absolute default of the credit scheduler if the 
   scheduler menu is not visible (2/5)

Changed since v1:
 * Marked credit2 as EXPERIMENTAL
 * Removed confusing language from the commit message
 * Alphabetize the schedulers
 * rename the __start and __end symbols to better match
   the rest of the file
 * Simplify the calculation of the number of schedulers
 * Make the scheduler ops structures static to their files


Jonathan Creekmore (5):
  build: Env var to enable expert config options
  build: Hook the schedulers into Kconfig
  build: Alloc space for sched list in the link file
  sched: Register the schedulers into the list
  sched: Use the auto-generated list of schedulers

 xen/Kconfig                 |  4 +++
 xen/Makefile                |  1 +
 xen/arch/arm/xen.lds.S      |  4 +++
 xen/arch/x86/xen.lds.S      |  4 +++
 xen/common/Kconfig          | 59 +++++++++++++++++++++++++++++++++++++++++++++
 xen/common/Makefile         |  8 +++---
 xen/common/sched_arinc653.c |  4 ++-
 xen/common/sched_credit.c   |  4 ++-
 xen/common/sched_credit2.c  |  4 ++-
 xen/common/sched_rt.c       |  4 ++-
 xen/common/schedule.c       | 19 ++++++---------
 xen/include/xen/sched-if.h  |  7 ++----
 12 files changed, 98 insertions(+), 24 deletions(-)

-- 
2.6.4

[PATCH v5 1/5] build: Env var to enable expert config options

[Jonathan Creekmore]

Add an additional environment variable, defaulting to disabled,
that enables the CONFIG_EXPERT configuration option. The purpose
of the CONFIG_EXPERT configuration option is to make non-standard
Kconfig options visible during the configuration process. The
CONFIG_EXPERT option is not, itself, visible during the Kconfig
configuration process, so typical users will never see it nor
any of the non-standard configuration options.

CC: Ian Campbell <ian.campbell@citrix.com>
CC: Ian Jackson <ian.jackson@eu.citrix.com>
CC: Jan Beulich <jbeulich@suse.com>
CC: Keir Fraser <keir@xen.org>
CC: Tim Deegan <tim@xen.org>
Signed-off-by: Jonathan Creekmore <jonathan.creekmore@gmail.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 xen/Kconfig  | 4 ++++
 xen/Makefile | 1 +
 2 files changed, 5 insertions(+)

diff --git a/xen/Kconfig b/xen/Kconfig
index ffe3f45..fa8b27c 100644
--- a/xen/Kconfig
+++ b/xen/Kconfig
@@ -22,3 +22,7 @@ config DEFCONFIG_LIST
 	string
 	option defconfig_list
 	default "$ARCH_DEFCONFIG"
+
+config EXPERT
+	string
+	option env="XEN_CONFIG_EXPERT"
diff --git a/xen/Makefile b/xen/Makefile
index 9023863..4950afb 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -11,6 +11,7 @@ export XEN_DOMAIN	?= $(shell ([ -x /bin/dnsdomainname ] && /bin/dnsdomainname) |
 export XEN_BUILD_DATE	?= $(shell LC_ALL=C date)
 export XEN_BUILD_TIME	?= $(shell LC_ALL=C date +%T)
 export XEN_BUILD_HOST	?= $(shell hostname)
+export XEN_CONFIG_EXPERT ?= n
 
 export BASEDIR := $(CURDIR)
 export XEN_ROOT := $(BASEDIR)/..
-- 
2.6.4

Re: [PATCH v5 1/5] build: Env var to enable expert config options

[Jan Beulich]

>>> On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
> --- a/xen/Kconfig
> +++ b/xen/Kconfig
> @@ -22,3 +22,7 @@ config DEFCONFIG_LIST
>  	string
>  	option defconfig_list
>  	default "$ARCH_DEFCONFIG"
> +
> +config EXPERT
> +	string
> +	option env="XEN_CONFIG_EXPERT"

This better wouldn't go in ahead of
http://lists.xenproject.org/archives/html/xen-devel/2016-01/msg01321.html
and would then need adjustment to take care of avoiding
re-introduction of that same problem.

Jan

Re: [PATCH v5 1/5] build: Env var to enable expert config options

[Ian Campbell]

On Thu, 2016-01-14 at 09:09 -0700, Jan Beulich wrote:
> > > > On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
> > --- a/xen/Kconfig
> > +++ b/xen/Kconfig
> > @@ -22,3 +22,7 @@ config DEFCONFIG_LIST
> >  	string
> >  	option defconfig_list
> >  	default "$ARCH_DEFCONFIG"
> > +
> > +config EXPERT
> > +	string
> > +	option env="XEN_CONFIG_EXPERT"
> 
> This better wouldn't go in ahead of
> http://lists.xenproject.org/archives/html/xen-devel/2016-01/msg01321.html
> and would then need adjustment to take care of avoiding
> re-introduction of that same problem.

I don't follow what problem would be reintroduced, this patch seems to be
correctly defining and exporting XEN_CONFIG_EXPERT from xen/Makefile before
any inclusion of kconfig related things

Ian.

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Re: [PATCH v5 1/5] build: Env var to enable expert config options

[Jan Beulich]

>>> On 15.01.16 at 16:47, <ian.campbell@citrix.com> wrote:
> On Thu, 2016-01-14 at 09:09 -0700, Jan Beulich wrote:
>> > > > On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
>> > --- a/xen/Kconfig
>> > +++ b/xen/Kconfig
>> > @@ -22,3 +22,7 @@ config DEFCONFIG_LIST
>> >  	string
>> >  	option defconfig_list
>> >  	default "$ARCH_DEFCONFIG"
>> > +
>> > +config EXPERT
>> > +	string
>> > +	option env="XEN_CONFIG_EXPERT"
>> 
>> This better wouldn't go in ahead of
>> http://lists.xenproject.org/archives/html/xen-devel/2016-01/msg01321.html 
>> and would then need adjustment to take care of avoiding
>> re-introduction of that same problem.
> 
> I don't follow what problem would be reintroduced, this patch seems to be
> correctly defining and exporting XEN_CONFIG_EXPERT from xen/Makefile before
> any inclusion of kconfig related things

Ah, wait, this variable comes from the environment in the first place,
and hence should be visible to Makefile.kconfig no matter what. I'm
sorry for the noise then.

Jan

[PATCH v5 2/5] build: Hook the schedulers into Kconfig

[Jonathan Creekmore]

Allow the schedulers to be independently enabled or disabled (except credit) 
at compile-time. To match existing behavior, all four schedulers are
compiled in by default, although the Credit2, RTDS, and ARINC653 are
marked EXPERIMENTAL to match their not currently supported status.

CC: George Dunlap <george.dunlap@eu.citrix.com>
CC: Dario Faggioli <dario.faggioli@citrix.com>
Signed-off-by: Jonathan Creekmore <jonathan.creekmore@gmail.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>

---
Changed since v4:

  * Removed the "if unsure" language
  * Removed ability to disable the "credit" scheduler
  * Remove stub vcpu_migration_delay functions since credit cannot be disabled

Changed since v2:

  * Hid the scheduler menu behind the EXPERT option
  * Provide static inlines for credit functions that are assumed to be
    always available
  * Provide an absolute default of the credit scheduler if the
    scheduler menu is not visible

Changed since v1:

  * Marked credit2 as EXPERIMENTAL
  * Removed confusing language from the commit message
  * Alphabetize the schedulers
---
 xen/common/Kconfig    | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++
 xen/common/Makefile   |  8 +++----
 xen/common/schedule.c | 12 +++++++++--
 3 files changed, 73 insertions(+), 6 deletions(-)

diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 046e257..286792a 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -51,4 +51,63 @@ config KEXEC
 
 	  If unsure, say Y.
 
+# Enable schedulers
+menu "Schedulers"
+	visible if EXPERT = "y"
+
+config SCHED_CREDIT
+	bool
+	default y
+	---help---
+	  The traditional credit scheduler is a general purpose scheduler.
+
+config SCHED_CREDIT2
+	bool "Credit2 scheduler support (EXPERIMENTAL)"
+	default y
+	---help---
+	  The credit2 scheduler is a general purpose scheduler that is
+	  optimized for lower latency and higher VM density.
+
+config SCHED_RTDS
+	bool "RTDS scheduler support (EXPERIMENTAL)"
+	default y
+	---help---
+	  The RTDS scheduler is a soft and firm real-time scheduler for
+	  multicore, targeted for embedded, automotive, graphics and gaming
+	  in the cloud, and general low-latency workloads.
+
+config SCHED_ARINC653
+	bool "ARINC653 scheduler support (EXPERIMENTAL)"
+	default y
+	---help---
+	  The ARINC653 scheduler is a hard real-time scheduler for single
+	  cores, targeted for avionics, drones, and medical devices.
+
+choice
+	prompt "Default Scheduler?"
+	default SCHED_CREDIT_DEFAULT if SCHED_CREDIT
+	default SCHED_CREDIT2_DEFAULT if SCHED_CREDIT2
+	default SCHED_RTDS_DEFAULT if SCHED_RTDS
+	default SCHED_ARINC653_DEFAULT if SCHED_ARINC653
+
+	config SCHED_CREDIT_DEFAULT
+		bool "Credit Scheduler" if SCHED_CREDIT
+	config SCHED_CREDIT2_DEFAULT
+		bool "Credit2 Scheduler" if SCHED_CREDIT2
+	config SCHED_RTDS_DEFAULT
+		bool "RT Scheduler" if SCHED_RTDS
+	config SCHED_ARINC653_DEFAULT
+		bool "ARINC653 Scheduler" if SCHED_ARINC653
+endchoice
+
+config SCHED_DEFAULT
+	string
+	default "credit" if SCHED_CREDIT_DEFAULT
+	default "credit2" if SCHED_CREDIT2_DEFAULT
+	default "rtds" if SCHED_RTDS_DEFAULT
+	default "arinc653" if SCHED_ARINC653_DEFAULT
+	default "credit"
+
+endmenu
+
 endmenu
diff --git a/xen/common/Makefile b/xen/common/Makefile
index 8ab15ba..29a5916 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -30,10 +30,10 @@ obj-y += rangeset.o
 obj-y += radix-tree.o
 obj-y += rbtree.o
 obj-y += rcupdate.o
-obj-y += sched_credit.o
-obj-y += sched_credit2.o
-obj-y += sched_arinc653.o
-obj-y += sched_rt.o
+obj-$(CONFIG_SCHED_ARINC653) += sched_arinc653.o
+obj-$(CONFIG_SCHED_CREDIT) += sched_credit.o
+obj-$(CONFIG_SCHED_CREDIT2) += sched_credit2.o
+obj-$(CONFIG_SCHED_RTDS) += sched_rt.o
 obj-y += schedule.o
 obj-y += shutdown.o
 obj-y += softirq.o
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index d121896..2f98a48 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -38,8 +38,8 @@
 #include <public/sched.h>
 #include <xsm/xsm.h>
 
-/* opt_sched: scheduler - default to credit */
-static char __initdata opt_sched[10] = "credit";
+/* opt_sched: scheduler - default to configured value */
+static char __initdata opt_sched[10] = CONFIG_SCHED_DEFAULT;
 string_param("sched", opt_sched);
 
 /* if sched_smt_power_savings is set,
@@ -65,10 +65,18 @@ DEFINE_PER_CPU(struct schedule_data, schedule_data);
 DEFINE_PER_CPU(struct scheduler *, scheduler);
 
 static const struct scheduler *schedulers[] = {
+#ifdef CONFIG_SCHED_CREDIT
     &sched_credit_def,
+#endif
+#ifdef CONFIG_SCHED_CREDIT2
     &sched_credit2_def,
+#endif
+#ifdef CONFIG_SCHED_ARINC653
     &sched_arinc653_def,
+#endif
+#ifdef CONFIG_SCHED_RTDS
     &sched_rtds_def,
+#endif
 };
 
 static struct scheduler __read_mostly ops;
-- 
2.6.4

Re: [PATCH v5 2/5] build: Hook the schedulers into Kconfig

[Jan Beulich]

>>> On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
> --- a/xen/common/Kconfig
> +++ b/xen/common/Kconfig
> @@ -51,4 +51,63 @@ config KEXEC
>  
>  	  If unsure, say Y.
>  
> +# Enable schedulers
> +menu "Schedulers"
> +	visible if EXPERT = "y"
> +
> +config SCHED_CREDIT
> +	bool
> +	default y
> +	---help---
> +	  The traditional credit scheduler is a general purpose scheduler.

So is this option now useful for anything?

> +choice
> +	prompt "Default Scheduler?"
> +	default SCHED_CREDIT_DEFAULT if SCHED_CREDIT
> +	default SCHED_CREDIT2_DEFAULT if SCHED_CREDIT2
> +	default SCHED_RTDS_DEFAULT if SCHED_RTDS
> +	default SCHED_ARINC653_DEFAULT if SCHED_ARINC653

And certainly all these defaults are now pointless, considering
that the condition of the first one is "if y".

Jan

Re: [PATCH v5 2/5] build: Hook the schedulers into Kconfig

[Jonathan Creekmore]

Jan Beulich writes:

>>>> On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
>> --- a/xen/common/Kconfig
>> +++ b/xen/common/Kconfig
>> @@ -51,4 +51,63 @@ config KEXEC
>>
>>  	  If unsure, say Y.
>>
>> +# Enable schedulers
>> +menu "Schedulers"
>> +	visible if EXPERT = "y"
>> +
>> +config SCHED_CREDIT
>> +	bool
>> +	default y
>> +	---help---
>> +	  The traditional credit scheduler is a general purpose scheduler.
>
> So is this option now useful for anything?

It keeps the code between all of the schedulers consistent (all of them
have a #define if they are compiled it) and helps keep my downstream
patch smaller.

>
>> +choice
>> +	prompt "Default Scheduler?"
>> +	default SCHED_CREDIT_DEFAULT if SCHED_CREDIT
>> +	default SCHED_CREDIT2_DEFAULT if SCHED_CREDIT2
>> +	default SCHED_RTDS_DEFAULT if SCHED_RTDS
>> +	default SCHED_ARINC653_DEFAULT if SCHED_ARINC653
>
> And certainly all these defaults are now pointless, considering
> that the condition of the first one is "if y".

Yes, I could rip all of those out now since credit is always the
default. I left it in there for the ideal case that credit didn't have
to be special cased but, at this point, I will rip it out if you want.

Re: [PATCH v5 2/5] build: Hook the schedulers into Kconfig

[Ian Campbell]

On Thu, 2016-01-14 at 10:23 -0600, Jonathan Creekmore wrote:
> Jan Beulich writes:
> 
> > > > > On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
> > > --- a/xen/common/Kconfig
> > > +++ b/xen/common/Kconfig
> > > @@ -51,4 +51,63 @@ config KEXEC
> > > 
> > >  	  If unsure, say Y.
> > > 
> > > +# Enable schedulers
> > > +menu "Schedulers"
> > > +	visible if EXPERT = "y"
> > > +
> > > +config SCHED_CREDIT
> > > +	bool
> > > +	default y
> > > +	---help---
> > > +	  The traditional credit scheduler is a general purpose
> > > scheduler.
> > 
> > So is this option now useful for anything?
> 
> It keeps the code between all of the schedulers consistent (all of them
> have a #define if they are compiled it)

FWIW I think this (consistency) is a reasonable argument for having this
option even if it doesn't actually do anything.

>  and helps keep my downstream
> patch smaller.
> 
> > 
> > > +choice
> > > +	prompt "Default Scheduler?"
> > > +	default SCHED_CREDIT_DEFAULT if SCHED_CREDIT
> > > +	default SCHED_CREDIT2_DEFAULT if SCHED_CREDIT2
> > > +	default SCHED_RTDS_DEFAULT if SCHED_RTDS
> > > +	default SCHED_ARINC653_DEFAULT if SCHED_ARINC653
> > 
> > And certainly all these defaults are now pointless, considering
> > that the condition of the first one is "if y".
> 
> Yes, I could rip all of those out now since credit is always the
> default. I left it in there for the ideal case that credit didn't have
> to be special cased but, at this point, I will rip it out if you want.

What is the behaviour of the above set of "default"s if more than one of
the SCHED_* is enabled? Does it pick the first, last, one at random?

If credit is now always the default I think that would be better expressed
with a single "default SCHED_CREDIT_DEFAULT".


Ian.

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Re: [PATCH v5 2/5] build: Hook the schedulers into Kconfig

[Jan Beulich]

>>> On 14.01.16 at 17:34, <ian.campbell@citrix.com> wrote:
> On Thu, 2016-01-14 at 10:23 -0600, Jonathan Creekmore wrote:
>> Jan Beulich writes:
>> 
>> > > > > On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
>> > > --- a/xen/common/Kconfig
>> > > +++ b/xen/common/Kconfig
>> > > @@ -51,4 +51,63 @@ config KEXEC
>> > > 
>> > >  	  If unsure, say Y.
>> > > 
>> > > +# Enable schedulers
>> > > +menu "Schedulers"
>> > > +	visible if EXPERT = "y"
>> > > +
>> > > +config SCHED_CREDIT
>> > > +	bool
>> > > +	default y
>> > > +	---help---
>> > > +	  The traditional credit scheduler is a general purpose
>> > > scheduler.
>> > 
>> > So is this option now useful for anything?
>> 
>> It keeps the code between all of the schedulers consistent (all of them
>> have a #define if they are compiled it)
> 
> FWIW I think this (consistency) is a reasonable argument for having this
> option even if it doesn't actually do anything.

While I can see your point, I dislike useless clutter in .config (also
on Linux, where I every once in a while send some cleanup
patches).

>> > > +choice
>> > > +	prompt "Default Scheduler?"
>> > > +	default SCHED_CREDIT_DEFAULT if SCHED_CREDIT
>> > > +	default SCHED_CREDIT2_DEFAULT if SCHED_CREDIT2
>> > > +	default SCHED_RTDS_DEFAULT if SCHED_RTDS
>> > > +	default SCHED_ARINC653_DEFAULT if SCHED_ARINC653
>> > 
>> > And certainly all these defaults are now pointless, considering
>> > that the condition of the first one is "if y".
>> 
>> Yes, I could rip all of those out now since credit is always the
>> default. I left it in there for the ideal case that credit didn't have
>> to be special cased but, at this point, I will rip it out if you want.
> 
> What is the behaviour of the above set of "default"s if more than one of
> the SCHED_* is enabled? Does it pick the first, last, one at random?

The first for which the condition is true.

> If credit is now always the default I think that would be better expressed
> with a single "default SCHED_CREDIT_DEFAULT".

Indeed.

Jan

Re: [PATCH v5 2/5] build: Hook the schedulers into Kconfig

[Ian Campbell]

On Thu, 2016-01-14 at 09:44 -0700, Jan Beulich wrote:
> > > > On 14.01.16 at 17:34, <ian.campbell@citrix.com> wrote:
> > On Thu, 2016-01-14 at 10:23 -0600, Jonathan Creekmore wrote:
> > > Jan Beulich writes:
> > > 
> > > > > > > On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
> > > > > --- a/xen/common/Kconfig
> > > > > +++ b/xen/common/Kconfig
> > > > > @@ -51,4 +51,63 @@ config KEXEC
> > > > > 
> > > > >  	  If unsure, say Y.
> > > > > 
> > > > > +# Enable schedulers
> > > > > +menu "Schedulers"
> > > > > +	visible if EXPERT = "y"
> > > > > +
> > > > > +config SCHED_CREDIT
> > > > > +	bool
> > > > > +	default y
> > > > > +	---help---
> > > > > +	  The traditional credit scheduler is a general purpose
> > > > > scheduler.
> > > > 
> > > > So is this option now useful for anything?
> > > 
> > > It keeps the code between all of the schedulers consistent (all of
> > > them
> > > have a #define if they are compiled it)
> > 
> > FWIW I think this (consistency) is a reasonable argument for having
> > this
> > option even if it doesn't actually do anything.
> 
> While I can see your point, I dislike useless clutter in .config (also
> on Linux, where I every once in a while send some cleanup
> patches).

I don't think this one is useless clutter, it provides useful information
to someone looking at the .config rather than then having to go and check
the source to find out what the defaults were.

Ian.

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Re: [PATCH v5 2/5] build: Hook the schedulers into Kconfig

[Jonathan Creekmore]

Jan Beulich writes:

>>>> On 14.01.16 at 17:34, <ian.campbell@citrix.com> wrote:
>> On Thu, 2016-01-14 at 10:23 -0600, Jonathan Creekmore wrote:
>>> Jan Beulich writes:
>>>
>>> > > > > On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
>>> > > --- a/xen/common/Kconfig
>>> > > +++ b/xen/common/Kconfig
>>> > > @@ -51,4 +51,63 @@ config KEXEC
>>> > >
>>> > >  	  If unsure, say Y.
>>> > >
>>> > > +# Enable schedulers
>>> > > +menu "Schedulers"
>>> > > +	visible if EXPERT = "y"
>>> > > +
>>> > > +config SCHED_CREDIT
>>> > > +	bool
>>> > > +	default y
>>> > > +	---help---
>>> > > +	  The traditional credit scheduler is a general purpose
>>> > > scheduler.
>>> >
>>> > So is this option now useful for anything?
>>>
>>> It keeps the code between all of the schedulers consistent (all of them
>>> have a #define if they are compiled it)
>>
>> FWIW I think this (consistency) is a reasonable argument for having this
>> option even if it doesn't actually do anything.
>
> While I can see your point, I dislike useless clutter in .config (also
> on Linux, where I every once in a while send some cleanup
> patches).
>
>>> > > +choice
>>> > > +	prompt "Default Scheduler?"
>>> > > +	default SCHED_CREDIT_DEFAULT if SCHED_CREDIT
>>> > > +	default SCHED_CREDIT2_DEFAULT if SCHED_CREDIT2
>>> > > +	default SCHED_RTDS_DEFAULT if SCHED_RTDS
>>> > > +	default SCHED_ARINC653_DEFAULT if SCHED_ARINC653
>>> >
>>> > And certainly all these defaults are now pointless, considering
>>> > that the condition of the first one is "if y".
>>>
>>> Yes, I could rip all of those out now since credit is always the
>>> default. I left it in there for the ideal case that credit didn't have
>>> to be special cased but, at this point, I will rip it out if you want.
>>
>> What is the behaviour of the above set of "default"s if more than one of
>> the SCHED_* is enabled? Does it pick the first, last, one at random?
>
> The first for which the condition is true.

Absolutely correct. The first true condition is the one that is chosen.

>> If credit is now always the default I think that would be better expressed
>> with a single "default SCHED_CREDIT_DEFAULT".
>
> Indeed.

And that is what I have already done for a v6 that I am sitting on to
see if I get more review comments.

[PATCH v5 3/5] build: Alloc space for sched list in the link file

[Jonathan Creekmore]

Creates a section to contain scheduler entry pointers that are gathered
together into an array. This will allow, in a follow-on patch, scheduler
entries to be automatically gathered together into the array for
automatic parsing.

CC: Ian Campbell <ian.campbell@citrix.com>
CC: Stefano Stabellini <stefano.stabellini@citrix.com>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <jbeulich@suse.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jonathan Creekmore <jonathan.creekmore@gmail.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

---
Changed since v4:
  * Remove defensive check for schedulers since the credit scheduler
    must always be present

Changed since v3:
  * Add defensive check for schedulers in the linker

Changed since v1:
  * rename the __start and __end symbols to better match
    the rest of the file
---
 xen/arch/arm/xen.lds.S | 4 ++++
 xen/arch/x86/xen.lds.S | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index 0488f37..f501a2f 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -57,6 +57,10 @@ SECTIONS
        . = ALIGN(PAGE_SIZE);
        *(.data.page_aligned)
        *(.data)
+       . = ALIGN(8);
+       __start_schedulers_array = .;
+       *(.data.schedulers)
+       __end_schedulers_array = .;
        *(.data.rel)
        *(.data.rel.*)
        CONSTRUCTORS
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index e18e08f..c1ce027 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -80,6 +80,10 @@ SECTIONS
        __stop___pre_ex_table = .;
 
        *(.data.read_mostly)
+       . = ALIGN(8);
+       __start_schedulers_array = .;
+       *(.data.schedulers)
+       __end_schedulers_array = .;
        *(.data.rel.ro)
        *(.data.rel.ro.*)
   } :text
-- 
2.6.4

[PATCH v5 4/5] sched: Register the schedulers into the list

[Jonathan Creekmore]

Adds a simple macro to place a pointer to a scheduler into an array
section at compile time. Also, goes ahead and generates the array
entries with each of the schedulers.

CC: George Dunlap <george.dunlap@eu.citrix.com>
CC: Dario Faggioli <dario.faggioli@citrix.com>
CC: Josh Whitehead <josh.whitehead@dornerworks.com>
CC: Robert VanVossen <robert.vanvossen@dornerworks.com>
Signed-off-by: Jonathan Creekmore <jonathan.creekmore@gmail.com>
Acked-by: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 xen/common/sched_arinc653.c | 2 ++
 xen/common/sched_credit.c   | 2 ++
 xen/common/sched_credit2.c  | 2 ++
 xen/common/sched_rt.c       | 2 ++
 xen/include/xen/sched-if.h  | 2 ++
 5 files changed, 10 insertions(+)

diff --git a/xen/common/sched_arinc653.c b/xen/common/sched_arinc653.c
index dbe02ed..3b59514 100644
--- a/xen/common/sched_arinc653.c
+++ b/xen/common/sched_arinc653.c
@@ -767,6 +767,8 @@ const struct scheduler sched_arinc653_def = {
     .tick_resume    = NULL,
 };
 
+REGISTER_SCHEDULER(sched_arinc653_def);
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index 0dce790..e586248 100644
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -2027,3 +2027,5 @@ const struct scheduler sched_credit_def = {
     .tick_suspend   = csched_tick_suspend,
     .tick_resume    = csched_tick_resume,
 };
+
+REGISTER_SCHEDULER(sched_credit_def);
diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
index 3c49ffa..38b02d0 100644
--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -2228,3 +2228,5 @@ const struct scheduler sched_credit2_def = {
     .alloc_domdata  = csched2_alloc_domdata,
     .free_domdata   = csched2_free_domdata,
 };
+
+REGISTER_SCHEDULER(sched_credit2_def);
diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
index 3f1d047..7640cd0 100644
--- a/xen/common/sched_rt.c
+++ b/xen/common/sched_rt.c
@@ -1199,3 +1199,5 @@ const struct scheduler sched_rtds_def = {
     .wake           = rt_vcpu_wake,
     .context_saved  = rt_context_saved,
 };
+
+REGISTER_SCHEDULER(sched_rtds_def);
diff --git a/xen/include/xen/sched-if.h b/xen/include/xen/sched-if.h
index 493d43f..9c6e0f5 100644
--- a/xen/include/xen/sched-if.h
+++ b/xen/include/xen/sched-if.h
@@ -170,6 +170,8 @@ extern const struct scheduler sched_credit2_def;
 extern const struct scheduler sched_arinc653_def;
 extern const struct scheduler sched_rtds_def;
 
+#define REGISTER_SCHEDULER(x) static const struct scheduler *x##_entry \
+  __used_section(".data.schedulers") = &x;
 
 struct cpupool
 {
-- 
2.6.4

[PATCH v5 5/5] sched: Use the auto-generated list of schedulers

[Jonathan Creekmore]

Instead of having a manually-curated list of schedulers, use the array
that was auto-generated simply by compiling in the scheduler files as
the sole source of truth of the available schedulers.

CC: George Dunlap <george.dunlap@eu.citrix.com>
CC: Dario Faggioli <dario.faggioli@citrix.com>
Signed-off-by: Jonathan Creekmore <jonathan.creekmore@gmail.com>
Acked-by: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>

---
Changed since v4:
  * Remove extra size field that was accidentally left in

Changed since v1:
  * Simplify the calculation of the number of schedulers
  * Make the scheduler ops structures static to their files
---
 xen/common/sched_arinc653.c |  2 +-
 xen/common/sched_credit.c   |  2 +-
 xen/common/sched_credit2.c  |  2 +-
 xen/common/sched_rt.c       |  2 +-
 xen/common/schedule.c       | 23 ++++++-----------------
 xen/include/xen/sched-if.h  |  5 -----
 6 files changed, 10 insertions(+), 26 deletions(-)

diff --git a/xen/common/sched_arinc653.c b/xen/common/sched_arinc653.c
index 3b59514..0606988 100644
--- a/xen/common/sched_arinc653.c
+++ b/xen/common/sched_arinc653.c
@@ -724,7 +724,7 @@ a653sched_adjust_global(const struct scheduler *ops,
  * callback functions.
  * The symbol must be visible to the rest of Xen at link time.
  */
-const struct scheduler sched_arinc653_def = {
+static const struct scheduler sched_arinc653_def = {
     .name           = "ARINC 653 Scheduler",
     .opt_name       = "arinc653",
     .sched_id       = XEN_SCHEDULER_ARINC653,
diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index e586248..028e41b 100644
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -1991,7 +1991,7 @@ static void csched_tick_resume(const struct scheduler *ops, unsigned int cpu)
 
 static struct csched_private _csched_priv;
 
-const struct scheduler sched_credit_def = {
+static const struct scheduler sched_credit_def = {
     .name           = "SMP Credit Scheduler",
     .opt_name       = "credit",
     .sched_id       = XEN_SCHEDULER_CREDIT,
diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
index 38b02d0..78220a7 100644
--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -2194,7 +2194,7 @@ csched2_deinit(const struct scheduler *ops)
 
 static struct csched2_private _csched2_priv;
 
-const struct scheduler sched_credit2_def = {
+static const struct scheduler sched_credit2_def = {
     .name           = "SMP Credit Scheduler rev2",
     .opt_name       = "credit2",
     .sched_id       = XEN_SCHEDULER_CREDIT2,
diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
index 7640cd0..2e5430f 100644
--- a/xen/common/sched_rt.c
+++ b/xen/common/sched_rt.c
@@ -1170,7 +1170,7 @@ rt_dom_cntl(
 
 static struct rt_private _rt_priv;
 
-const struct scheduler sched_rtds_def = {
+static const struct scheduler sched_rtds_def = {
     .name           = "SMP RTDS Scheduler",
     .opt_name       = "rtds",
     .sched_id       = XEN_SCHEDULER_RTDS,
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 2f98a48..0232179 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -64,20 +64,9 @@ static void poll_timer_fn(void *data);
 DEFINE_PER_CPU(struct schedule_data, schedule_data);
 DEFINE_PER_CPU(struct scheduler *, scheduler);
 
-static const struct scheduler *schedulers[] = {
-#ifdef CONFIG_SCHED_CREDIT
-    &sched_credit_def,
-#endif
-#ifdef CONFIG_SCHED_CREDIT2
-    &sched_credit2_def,
-#endif
-#ifdef CONFIG_SCHED_ARINC653
-    &sched_arinc653_def,
-#endif
-#ifdef CONFIG_SCHED_RTDS
-    &sched_rtds_def,
-#endif
-};
+extern const struct scheduler *__start_schedulers_array[], *__end_schedulers_array[];
+#define NUM_SCHEDULERS (__end_schedulers_array - __start_schedulers_array)
+static const struct scheduler **schedulers = __start_schedulers_array;
 
 static struct scheduler __read_mostly ops;
 
@@ -1468,7 +1457,7 @@ void __init scheduler_init(void)
 
     open_softirq(SCHEDULE_SOFTIRQ, schedule);
 
-    for ( i = 0; i < ARRAY_SIZE(schedulers); i++ )
+    for ( i = 0; i < NUM_SCHEDULERS; i++)
     {
         if ( schedulers[i]->global_init && schedulers[i]->global_init() < 0 )
             schedulers[i] = NULL;
@@ -1479,7 +1468,7 @@ void __init scheduler_init(void)
     if ( !ops.name )
     {
         printk("Could not find scheduler: %s\n", opt_sched);
-        for ( i = 0; i < ARRAY_SIZE(schedulers); i++ )
+        for ( i = 0; i < NUM_SCHEDULERS; i++ )
             if ( schedulers[i] )
             {
                 ops = *schedulers[i];
@@ -1599,7 +1588,7 @@ struct scheduler *scheduler_alloc(unsigned int sched_id, int *perr)
     int i;
     struct scheduler *sched;
 
-    for ( i = 0; i < ARRAY_SIZE(schedulers); i++ )
+    for ( i = 0; i < NUM_SCHEDULERS; i++ )
         if ( schedulers[i] && schedulers[i]->sched_id == sched_id )
             goto found;
     *perr = -ENOENT;
diff --git a/xen/include/xen/sched-if.h b/xen/include/xen/sched-if.h
index 9c6e0f5..66dc9c8 100644
--- a/xen/include/xen/sched-if.h
+++ b/xen/include/xen/sched-if.h
@@ -165,11 +165,6 @@ struct scheduler {
     void         (*tick_resume)     (const struct scheduler *, unsigned int);
 };
 
-extern const struct scheduler sched_credit_def;
-extern const struct scheduler sched_credit2_def;
-extern const struct scheduler sched_arinc653_def;
-extern const struct scheduler sched_rtds_def;
-
 #define REGISTER_SCHEDULER(x) static const struct scheduler *x##_entry \
   __used_section(".data.schedulers") = &x;
 
-- 
2.6.4

Re: [PATCH v5 5/5] sched: Use the auto-generated list of schedulers

[Jan Beulich]

>>> On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
> --- a/xen/common/schedule.c
> +++ b/xen/common/schedule.c
> @@ -64,20 +64,9 @@ static void poll_timer_fn(void *data);
>  DEFINE_PER_CPU(struct schedule_data, schedule_data);
>  DEFINE_PER_CPU(struct scheduler *, scheduler);
>  
> -static const struct scheduler *schedulers[] = {
> -#ifdef CONFIG_SCHED_CREDIT
> -    &sched_credit_def,
> -#endif
> -#ifdef CONFIG_SCHED_CREDIT2
> -    &sched_credit2_def,
> -#endif
> -#ifdef CONFIG_SCHED_ARINC653
> -    &sched_arinc653_def,
> -#endif
> -#ifdef CONFIG_SCHED_RTDS
> -    &sched_rtds_def,
> -#endif
> -};
> +extern const struct scheduler *__start_schedulers_array[], 
> *__end_schedulers_array[];
> +#define NUM_SCHEDULERS (__end_schedulers_array - __start_schedulers_array)
> +static const struct scheduler **schedulers = __start_schedulers_array;

#define or properly constified (to help the compiler recognize it
won't ever change).

Jan

Re: [PATCH v5 5/5] sched: Use the auto-generated list of schedulers

[Jonathan Creekmore]

Jan Beulich writes:

>>>> On 14.01.16 at 15:49, <jonathan.creekmore@gmail.com> wrote:
>> --- a/xen/common/schedule.c
>> +++ b/xen/common/schedule.c
>> @@ -64,20 +64,9 @@ static void poll_timer_fn(void *data);
>>  DEFINE_PER_CPU(struct schedule_data, schedule_data);
>>  DEFINE_PER_CPU(struct scheduler *, scheduler);
>>
>> -static const struct scheduler *schedulers[] = {
>> -#ifdef CONFIG_SCHED_CREDIT
>> -    &sched_credit_def,
>> -#endif
>> -#ifdef CONFIG_SCHED_CREDIT2
>> -    &sched_credit2_def,
>> -#endif
>> -#ifdef CONFIG_SCHED_ARINC653
>> -    &sched_arinc653_def,
>> -#endif
>> -#ifdef CONFIG_SCHED_RTDS
>> -    &sched_rtds_def,
>> -#endif
>> -};
>> +extern const struct scheduler *__start_schedulers_array[],
>> *__end_schedulers_array[];
>> +#define NUM_SCHEDULERS (__end_schedulers_array - __start_schedulers_array)
>> +static const struct scheduler **schedulers = __start_schedulers_array;
>
> #define or properly constified (to help the compiler recognize it
> won't ever change).

I will make it a define in the next version.