[RESEND PATCH 0/4] Remove elevator kernel parameter

[RESEND PATCH 0/4] Remove elevator kernel parameter

[Marcos Paulo de Souza]

This is just a resend, now with reviews by Hannes and Bob in place. These
patches were based in linux-block/for-next branch.

Original cover letter:
After the first patch sent[1], together with some background from Jens[2], this
patchset aims to remove completely elevator kernel parameter, since it is not
being used since blk-mq was set by default.

Along with elevator code, some documentation was also updated to remove elevator
references.

[1]: https://lkml.org/lkml/2019/7/12/1008
[2]: https://lkml.org/lkml/2019/7/13/232

Marcos Paulo de Souza (4):
  block: elevator.c: Remove now unused elevator= argument
  kernel-parameters.txt: Remove elevator argument
  Documenation: switching-sched: Remove notes about elevator argument
  Documentation:kernel-per-CPU-kthreads.txt: Remove reference to
    elevator=

 Documentation/admin-guide/kernel-parameters.txt |  6 ------
 Documentation/block/switching-sched.txt         |  4 ----
 Documentation/kernel-per-CPU-kthreads.txt       |  8 +++-----
 block/elevator.c                                | 14 --------------
 4 files changed, 3 insertions(+), 29 deletions(-)

-- 
2.22.0

[RESEND PATCH 1/4] block: elevator.c: Remove now unused elevator= argument

[Marcos Paulo de Souza]

Since the inclusion of blk-mq, elevator argument was not being
considered anymore, and it's utility died long with the legacy IO path,
now removed too.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
---
 block/elevator.c | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/block/elevator.c b/block/elevator.c
index 2f17d66d0e61..f56d9c7d5cbc 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -135,20 +135,6 @@ static struct elevator_type *elevator_get(struct request_queue *q,
 	return e;
 }
 
-static char chosen_elevator[ELV_NAME_MAX];
-
-static int __init elevator_setup(char *str)
-{
-	/*
-	 * Be backwards-compatible with previous kernels, so users
-	 * won't get the wrong elevator.
-	 */
-	strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
-	return 1;
-}
-
-__setup("elevator=", elevator_setup);
-
 static struct kobj_type elv_ktype;
 
 struct elevator_queue *elevator_alloc(struct request_queue *q,
-- 
2.22.0

[RESEND PATCH 2/4] kernel-parameters.txt: Remove elevator argument

[Marcos Paulo de Souza]

This argument was not being used since the legacy IO path was removed,
when blk-mq was enabled by default. So removed it from the kernel
parameters documentation.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f1c433daef6b..7d2738c7d49b 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1199,12 +1199,6 @@
 			See comment before function elanfreq_setup() in
 			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 
-	elevator=	[IOSCHED]
-			Format: { "mq-deadline" | "kyber" | "bfq" }
-			See Documentation/block/deadline-iosched.txt,
-			Documentation/block/kyber-iosched.txt and
-			Documentation/block/bfq-iosched.txt for details.
-
 	elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
 			Specifies physical address of start of kernel core
 			image elf header and optionally the size. Generally
-- 
2.22.0

[RESEND PATCH 3/4] Documenation: switching-sched: Remove notes about elevator argument

[Marcos Paulo de Souza]

This argument was ignored since blk-mq was set as default, so remove it
from documentation.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
---
 Documentation/block/switching-sched.txt | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/Documentation/block/switching-sched.txt b/Documentation/block/switching-sched.txt
index 7977f6fb8b20..431d56471227 100644
--- a/Documentation/block/switching-sched.txt
+++ b/Documentation/block/switching-sched.txt
@@ -1,7 +1,3 @@
-To choose IO schedulers at boot time, use the argument 'elevator=deadline'.
-'noop' and 'cfq' (the default) are also available. IO schedulers are assigned
-globally at boot time only presently.
-
 Each io queue has a set of io scheduler tunables associated with it. These
 tunables control how the io scheduler works. You can find these entries
 in:
-- 
2.22.0

[RESEND PATCH 4/4] Documentation:kernel-per-CPU-kthreads.txt: Remove reference to elevator=

[Marcos Paulo de Souza]

This argument was not being considered since blk-mq was set by default,
so removed this documentation to avoid confusion.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
---
 Documentation/kernel-per-CPU-kthreads.txt | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt
index 5623b9916411..c68c6c8c26a4 100644
--- a/Documentation/kernel-per-CPU-kthreads.txt
+++ b/Documentation/kernel-per-CPU-kthreads.txt
@@ -274,9 +274,7 @@ To reduce its OS jitter, do any of the following:
 		(based on an earlier one from Gilad Ben-Yossef) that
 		reduces or even eliminates vmstat overhead for some
 		workloads at https://lkml.org/lkml/2013/9/4/379.
-	e.	Boot with "elevator=noop" to avoid workqueue use by
-		the block layer.
-	f.	If running on high-end powerpc servers, build with
+	e.	If running on high-end powerpc servers, build with
 		CONFIG_PPC_RTAS_DAEMON=n.  This prevents the RTAS
 		daemon from running on each CPU every second or so.
 		(This will require editing Kconfig files and will defeat
@@ -284,12 +282,12 @@ To reduce its OS jitter, do any of the following:
 		due to the rtas_event_scan() function.
 		WARNING:  Please check your CPU specifications to
 		make sure that this is safe on your particular system.
-	g.	If running on Cell Processor, build your kernel with
+	f.	If running on Cell Processor, build your kernel with
 		CBE_CPUFREQ_SPU_GOVERNOR=n to avoid OS jitter from
 		spu_gov_work().
 		WARNING:  Please check your CPU specifications to
 		make sure that this is safe on your particular system.
-	h.	If running on PowerMAC, build your kernel with
+	g.	If running on PowerMAC, build your kernel with
 		CONFIG_PMAC_RACKMETER=n to disable the CPU-meter,
 		avoiding OS jitter from rackmeter_do_timer().
 
-- 
2.22.0

[PATCH v2 0/4] Remove elevator kernel parameter

[Marcos Paulo de Souza]

Since the last RESEND[1], I found that I used an old block/for-next to base my
changes. This version is just a rebase over
8ba64588ef2136ff7561fb2047d53debed8a7b56 ("Merge branch 'for-5.4/libata' into
for-next"), solving minor conflicts.

Original cover letter:
After the first patch sent[2], together with some background from Jens[3], this
patchset aims to remove completely elevator kernel parameter, since it is not
being used since blk-mq was set by default.

Along with elevator code, some documentation was also updated to remove elevator
references.

[1]: https://lkml.org/lkml/2019/8/27/1648
[2]: https://lkml.org/lkml/2019/7/12/1008
[3]: https://lkml.org/lkml/2019/7/13/232

Marcos Paulo de Souza (4):
  block: elevator.c: Remove now unused elevator= argument
  kernel-parameters.txt: Remove elevator argument
  Documenation: switching-sched: Remove notes about elevator argument
  Documentation:kernel-per-CPU-kthreads.txt: Remove reference to
    elevator=

 Documentation/admin-guide/kernel-parameters.txt    |  6 ------
 .../admin-guide/kernel-per-CPU-kthreads.rst        |  8 +++-----
 Documentation/block/switching-sched.rst            |  4 ----
 block/elevator.c                                   | 14 --------------
 4 files changed, 3 insertions(+), 29 deletions(-)

-- 
2.22.0

[PATCH v2 1/4] block: elevator.c: Remove now unused elevator= argument

[Marcos Paulo de Souza]

Since the inclusion of blk-mq, elevator argument was not being
considered anymore, and it's utility died long with the legacy IO path,
now removed too.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
---
 block/elevator.c | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/block/elevator.c b/block/elevator.c
index 4781c4205a5d..86100de88883 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -135,20 +135,6 @@ static struct elevator_type *elevator_get(struct request_queue *q,
 	return e;
 }
 
-static char chosen_elevator[ELV_NAME_MAX];
-
-static int __init elevator_setup(char *str)
-{
-	/*
-	 * Be backwards-compatible with previous kernels, so users
-	 * won't get the wrong elevator.
-	 */
-	strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
-	return 1;
-}
-
-__setup("elevator=", elevator_setup);
-
 static struct kobj_type elv_ktype;
 
 struct elevator_queue *elevator_alloc(struct request_queue *q,
-- 
2.22.0

Re: [PATCH v2 1/4] block: elevator.c: Remove now unused elevator= argument

[Christoph Hellwig]

On Sun, Sep 01, 2019 at 08:29:13PM -0300, Marcos Paulo de Souza wrote:
> Since the inclusion of blk-mq, elevator argument was not being
> considered anymore, and it's utility died long with the legacy IO path,
> now removed too.
> 
> Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
> Reviewed-by: Hannes Reinecke <hare@suse.com>
> Reviewed-by: Bob Liu <bob.liu@oracle.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH v2 2/4] kernel-parameters.txt: Remove elevator argument

[Marcos Paulo de Souza]

This argument was not being used since the legacy IO path was removed,
when blk-mq was enabled by default. So removed it from the kernel
parameters documentation.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 4c1971960afa..6f2bc0e02421 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1197,12 +1197,6 @@
 			See comment before function elanfreq_setup() in
 			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 
-	elevator=	[IOSCHED]
-			Format: { "mq-deadline" | "kyber" | "bfq" }
-			See Documentation/block/deadline-iosched.rst,
-			Documentation/block/kyber-iosched.rst and
-			Documentation/block/bfq-iosched.rst for details.
-
 	elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
 			Specifies physical address of start of kernel core
 			image elf header and optionally the size. Generally
-- 
2.22.0

Re: [PATCH v2 2/4] kernel-parameters.txt: Remove elevator argument

[Christoph Hellwig]

On Sun, Sep 01, 2019 at 08:29:14PM -0300, Marcos Paulo de Souza wrote:
> This argument was not being used since the legacy IO path was removed,
> when blk-mq was enabled by default. So removed it from the kernel
> parameters documentation.
> 
> Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
> Reviewed-by: Hannes Reinecke <hare@suse.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

That beeing said I would have folded it into the previous patch.

[PATCH v2 3/4] Documenation: switching-sched: Remove notes about elevator argument

[Marcos Paulo de Souza]

This argument was ignored since blk-mq was set as default, so remove it
from documentation.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
---
 Documentation/block/switching-sched.rst | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/Documentation/block/switching-sched.rst b/Documentation/block/switching-sched.rst
index 42042417380e..520f6b857544 100644
--- a/Documentation/block/switching-sched.rst
+++ b/Documentation/block/switching-sched.rst
@@ -2,10 +2,6 @@
 Switching Scheduler
 ===================
 
-To choose IO schedulers at boot time, use the argument 'elevator=deadline'.
-'noop' and 'cfq' (the default) are also available. IO schedulers are assigned
-globally at boot time only presently.
-
 Each io queue has a set of io scheduler tunables associated with it. These
 tunables control how the io scheduler works. You can find these entries
 in::
-- 
2.22.0

Re: [PATCH v2 3/4] Documenation: switching-sched: Remove notes about elevator argument

[Christoph Hellwig]

On Sun, Sep 01, 2019 at 08:29:15PM -0300, Marcos Paulo de Souza wrote:
> This argument was ignored since blk-mq was set as default, so remove it
> from documentation.
> 
> Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
> Reviewed-by: Hannes Reinecke <hare@suse.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH v2 4/4] Documentation:kernel-per-CPU-kthreads.txt: Remove reference to elevator=

[Marcos Paulo de Souza]

This argument was not being considered since blk-mq was set by default,
so removed this documentation to avoid confusion.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
---
 Documentation/admin-guide/kernel-per-CPU-kthreads.rst | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst
index 4f18456dd3b1..baeeba8762ae 100644
--- a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst
+++ b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst
@@ -274,9 +274,7 @@ To reduce its OS jitter, do any of the following:
 		(based on an earlier one from Gilad Ben-Yossef) that
 		reduces or even eliminates vmstat overhead for some
 		workloads at https://lkml.org/lkml/2013/9/4/379.
-	e.	Boot with "elevator=noop" to avoid workqueue use by
-		the block layer.
-	f.	If running on high-end powerpc servers, build with
+	e.	If running on high-end powerpc servers, build with
 		CONFIG_PPC_RTAS_DAEMON=n.  This prevents the RTAS
 		daemon from running on each CPU every second or so.
 		(This will require editing Kconfig files and will defeat
@@ -284,12 +282,12 @@ To reduce its OS jitter, do any of the following:
 		due to the rtas_event_scan() function.
 		WARNING:  Please check your CPU specifications to
 		make sure that this is safe on your particular system.
-	g.	If running on Cell Processor, build your kernel with
+	f.	If running on Cell Processor, build your kernel with
 		CBE_CPUFREQ_SPU_GOVERNOR=n to avoid OS jitter from
 		spu_gov_work().
 		WARNING:  Please check your CPU specifications to
 		make sure that this is safe on your particular system.
-	h.	If running on PowerMAC, build your kernel with
+	g.	If running on PowerMAC, build your kernel with
 		CONFIG_PMAC_RACKMETER=n to disable the CPU-meter,
 		avoiding OS jitter from rackmeter_do_timer().
 
-- 
2.22.0

Re: [PATCH v2 4/4] Documentation:kernel-per-CPU-kthreads.txt: Remove reference to elevator=

[Christoph Hellwig]

On Sun, Sep 01, 2019 at 08:29:16PM -0300, Marcos Paulo de Souza wrote:
> This argument was not being considered since blk-mq was set by default,
> so removed this documentation to avoid confusion.
> 
> Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
> Reviewed-by: Hannes Reinecke <hare@suse.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [RESEND PATCH 0/4] Remove elevator kernel parameter

[Jens Axboe]

On 8/27/19 7:19 PM, Marcos Paulo de Souza wrote:
> This is just a resend, now with reviews by Hannes and Bob in place. These
> patches were based in linux-block/for-next branch.
> 
> Original cover letter:
> After the first patch sent[1], together with some background from Jens[2], this
> patchset aims to remove completely elevator kernel parameter, since it is not
> being used since blk-mq was set by default.
> 
> Along with elevator code, some documentation was also updated to remove elevator
> references.

Applied, but:

1) Folded patch 1+2
2) Patch 3+4 .txt files are dead

-- 
Jens Axboe