[PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Yury Norov]

for_each_cpu() is widely used in kernel, and it's beneficial to create
a NUMA-aware version of the macro.

Recently added for_each_numa_hop_mask() works, but switching existing
codebase to it is not an easy process.

This series adds for_each_numa_cpu(), which is designed to be similar to
the for_each_cpu(). It allows to convert existing code to NUMA-aware as
simple as adding a hop iterator variable and passing it inside new macro.
for_each_numa_cpu() takes care of the rest.

At the moment, we have 2 users of NUMA-aware enumerators. One is
Melanox's in-tree driver, and another is Intel's in-review driver:

https://lore.kernel.org/lkml/20230216145455.661709-1-pawel.chmielewski@intel.com/

Both real-life examples follow the same pattern:

        for_each_numa_hop_mask(cpus, prev, node) {
                for_each_cpu_andnot(cpu, cpus, prev) {
                        if (cnt++ == max_num)
                                goto out;
                        do_something(cpu);
                }
                prev = cpus;
        }

With the new macro, it has a more standard look, like this:

        for_each_numa_cpu(cpu, hop, node, cpu_possible_mask) {
                if (cnt++ == max_num)
                        break;
                do_something(cpu);
        }

Straight conversion of existing for_each_cpu() codebase to NUMA-aware
version with for_each_numa_hop_mask() is difficult because it doesn't
take a user-provided cpu mask, and eventually ends up with open-coded
double loop. With for_each_numa_cpu() it shouldn't be a brainteaser.
Consider the NUMA-ignorant example:

        cpumask_t cpus = get_mask();
        int cnt = 0, cpu;

        for_each_cpu(cpu, cpus) {
                if (cnt++ == max_num)
                        break;
                do_something(cpu);
        }

Converting it to NUMA-aware version would be as simple as:

        cpumask_t cpus = get_mask();
        int node = get_node();
        int cnt = 0, hop, cpu;

        for_each_numa_cpu(cpu, hop, node, cpus) {
                if (cnt++ == max_num)
                        break;
                do_something(cpu);
        }

The latter looks more verbose and avoids from open-coding that annoying
double loop. Another advantage is that it works with a 'hop' parameter with
the clear meaning of NUMA distance, and doesn't make people not familiar
to enumerator internals bothering with current and previous masks machinery.

v2:
 - repase on top of master;
 - cleanup comments and tweak them to comply with kernel-doc;
 - remove RFC from patch #8 as there's no objections.

Yury Norov (8):
  lib/find: add find_next_and_andnot_bit()
  sched/topology: introduce sched_numa_find_next_cpu()
  sched/topology: add for_each_numa_cpu() macro
  net: mlx5: switch comp_irqs_request() to using for_each_numa_cpu
  lib/cpumask: update comment to cpumask_local_spread()
  sched/topology: export sched_domains_numa_levels
  lib: add test for for_each_numa_{cpu,hop_mask}()
  sched: drop for_each_numa_hop_mask()

 drivers/net/ethernet/mellanox/mlx5/core/eq.c | 16 ++----
 include/linux/find.h                         | 43 ++++++++++++++
 include/linux/topology.h                     | 37 ++++++------
 kernel/sched/topology.c                      | 59 +++++++++++---------
 lib/cpumask.c                                |  7 +--
 lib/find_bit.c                               | 12 ++++
 lib/test_bitmap.c                            | 16 ++++++
 7 files changed, 133 insertions(+), 57 deletions(-)

-- 
2.34.1

Re: [PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Peter Zijlstra]

Something went wrong with sending your patches; I only have 0/n.

Re: [PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Yury Norov]

On Mon, Apr 17, 2023 at 01:11:37PM +0200, Peter Zijlstra wrote:
> 
> 
> Something went wrong with sending your patches; I only have 0/n.

Indeed. Thanks for pointing. I'll resend shortly.

[PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Yury Norov]

for_each_cpu() is widely used in kernel, and it's beneficial to create
a NUMA-aware version of the macro.

Recently added for_each_numa_hop_mask() works, but switching existing
codebase to it is not an easy process.

This series adds for_each_numa_cpu(), which is designed to be similar to
the for_each_cpu(). It allows to convert existing code to NUMA-aware as
simple as adding a hop iterator variable and passing it inside new macro.
for_each_numa_cpu() takes care of the rest.

At the moment, we have 2 users of NUMA-aware enumerators. One is
Melanox's in-tree driver, and another is Intel's in-review driver:

https://lore.kernel.org/lkml/20230216145455.661709-1-pawel.chmielewski@intel.com/

Both real-life examples follow the same pattern:

        for_each_numa_hop_mask(cpus, prev, node) {
                for_each_cpu_andnot(cpu, cpus, prev) {
                        if (cnt++ == max_num)
                                goto out;
                        do_something(cpu);
                }
                prev = cpus;
        }

With the new macro, it has a more standard look, like this:

        for_each_numa_cpu(cpu, hop, node, cpu_possible_mask) {
                if (cnt++ == max_num)
                        break;
                do_something(cpu);
        }

Straight conversion of existing for_each_cpu() codebase to NUMA-aware
version with for_each_numa_hop_mask() is difficult because it doesn't
take a user-provided cpu mask, and eventually ends up with open-coded
double loop. With for_each_numa_cpu() it shouldn't be a brainteaser.
Consider the NUMA-ignorant example:

        cpumask_t cpus = get_mask();
        int cnt = 0, cpu;

        for_each_cpu(cpu, cpus) {
                if (cnt++ == max_num)
                        break;
                do_something(cpu);
        }

Converting it to NUMA-aware version would be as simple as:

        cpumask_t cpus = get_mask();
        int node = get_node();
        int cnt = 0, hop, cpu;

        for_each_numa_cpu(cpu, hop, node, cpus) {
                if (cnt++ == max_num)
                        break;
                do_something(cpu);
        }

The latter looks more verbose and avoids from open-coding that annoying
double loop. Another advantage is that it works with a 'hop' parameter with
the clear meaning of NUMA distance, and doesn't make people not familiar
to enumerator internals bothering with current and previous masks machinery.

v2:
 - repase on top of master;
 - cleanup comments and tweak them to comply with kernel-doc;
 - remove RFC from patch #8 as there's no objections.

Yury Norov (8):
  lib/find: add find_next_and_andnot_bit()
  sched/topology: introduce sched_numa_find_next_cpu()
  sched/topology: add for_each_numa_cpu() macro
  net: mlx5: switch comp_irqs_request() to using for_each_numa_cpu
  lib/cpumask: update comment to cpumask_local_spread()
  sched/topology: export sched_domains_numa_levels
  lib: add test for for_each_numa_{cpu,hop_mask}()
  sched: drop for_each_numa_hop_mask()

 drivers/net/ethernet/mellanox/mlx5/core/eq.c | 16 ++----
 include/linux/find.h                         | 43 ++++++++++++++
 include/linux/topology.h                     | 37 ++++++------
 kernel/sched/topology.c                      | 59 +++++++++++---------
 lib/cpumask.c                                |  7 +--
 lib/find_bit.c                               | 12 ++++
 lib/test_bitmap.c                            | 16 ++++++
 7 files changed, 133 insertions(+), 57 deletions(-)

-- 
2.34.1

[PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Yury Norov]

for_each_cpu() is widely used in kernel, and it's beneficial to create
a NUMA-aware version of the macro.

Recently added for_each_numa_hop_mask() works, but switching existing
codebase to it is not an easy process.

This series adds for_each_numa_cpu(), which is designed to be similar to
the for_each_cpu(). It allows to convert existing code to NUMA-aware as
simple as adding a hop iterator variable and passing it inside new macro.
for_each_numa_cpu() takes care of the rest.

At the moment, we have 2 users of NUMA-aware enumerators. One is
Melanox's in-tree driver, and another is Intel's in-review driver:

https://lore.kernel.org/lkml/20230216145455.661709-1-pawel.chmielewski@intel.com/

Both real-life examples follow the same pattern:

        for_each_numa_hop_mask(cpus, prev, node) {
                for_each_cpu_andnot(cpu, cpus, prev) {
                        if (cnt++ == max_num)
                                goto out;
                        do_something(cpu);
                }
                prev = cpus;
        }

With the new macro, it has a more standard look, like this:

        for_each_numa_cpu(cpu, hop, node, cpu_possible_mask) {
                if (cnt++ == max_num)
                        break;
                do_something(cpu);
        }

Straight conversion of existing for_each_cpu() codebase to NUMA-aware
version with for_each_numa_hop_mask() is difficult because it doesn't
take a user-provided cpu mask, and eventually ends up with open-coded
double loop. With for_each_numa_cpu() it shouldn't be a brainteaser.
Consider the NUMA-ignorant example:

        cpumask_t cpus = get_mask();
        int cnt = 0, cpu;

        for_each_cpu(cpu, cpus) {
                if (cnt++ == max_num)
                        break;
                do_something(cpu);
        }

Converting it to NUMA-aware version would be as simple as:

        cpumask_t cpus = get_mask();
        int node = get_node();
        int cnt = 0, hop, cpu;

        for_each_numa_cpu(cpu, hop, node, cpus) {
                if (cnt++ == max_num)
                        break;
                do_something(cpu);
        }

The latter looks more verbose and avoids from open-coding that annoying
double loop. Another advantage is that it works with a 'hop' parameter with
the clear meaning of NUMA distance, and doesn't make people not familiar
to enumerator internals bothering with current and previous masks machinery.

v2: https://lore.kernel.org/netdev/ZD3l6FBnUh9vTIGc@yury-ThinkPad/T/
v3:
 - fix sched_numa_find_{next,nth}_cpu() when CONFIG_NUMA is off to
   only traverse online CPUs;
 - don't export sched_domains_numa_levels for testing purposes. In
   the test, use for_each_node() macro;
 - extend the test for for_each_node();
 - in comments, mention that only online CPUs are traversed;
 - rebase on top of 6.3. 

Yury Norov (8):
  sched: fix sched_numa_find_nth_cpu() in non-NUMA case
  lib/find: add find_next_and_andnot_bit()
  sched/topology: introduce sched_numa_find_next_cpu()
  sched/topology: add for_each_numa_{,online}_cpu() macro
  net: mlx5: switch comp_irqs_request() to using for_each_numa_cpu
  lib/cpumask: update comment to cpumask_local_spread()
  sched: drop for_each_numa_hop_mask()
  lib: test for_each_numa_cpus()

 drivers/net/ethernet/mellanox/mlx5/core/eq.c | 16 ++---
 include/linux/find.h                         | 43 ++++++++++++
 include/linux/topology.h                     | 40 ++++++-----
 kernel/sched/topology.c                      | 53 ++++++++-------
 lib/cpumask.c                                |  7 +-
 lib/find_bit.c                               | 12 ++++
 lib/test_bitmap.c                            | 70 +++++++++++++++++++-
 7 files changed, 183 insertions(+), 58 deletions(-)

-- 
2.37.2

Re: [PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Valentin Schneider]

On 30/04/23 10:18, Yury Norov wrote:
> for_each_cpu() is widely used in kernel, and it's beneficial to create
> a NUMA-aware version of the macro.
>
> Recently added for_each_numa_hop_mask() works, but switching existing
> codebase to it is not an easy process.
>
> This series adds for_each_numa_cpu(), which is designed to be similar to
> the for_each_cpu(). It allows to convert existing code to NUMA-aware as
> simple as adding a hop iterator variable and passing it inside new macro.
> for_each_numa_cpu() takes care of the rest.
>
> At the moment, we have 2 users of NUMA-aware enumerators. One is
> Melanox's in-tree driver, and another is Intel's in-review driver:
>
> https://lore.kernel.org/lkml/20230216145455.661709-1-pawel.chmielewski@intel.com/
>
> Both real-life examples follow the same pattern:
>
>         for_each_numa_hop_mask(cpus, prev, node) {
>                 for_each_cpu_andnot(cpu, cpus, prev) {
>                         if (cnt++ == max_num)
>                                 goto out;
>                         do_something(cpu);
>                 }
>                 prev = cpus;
>         }
>
> With the new macro, it has a more standard look, like this:
>
>         for_each_numa_cpu(cpu, hop, node, cpu_possible_mask) {
>                 if (cnt++ == max_num)
>                         break;
>                 do_something(cpu);
>         }
>
> Straight conversion of existing for_each_cpu() codebase to NUMA-aware
> version with for_each_numa_hop_mask() is difficult because it doesn't
> take a user-provided cpu mask, and eventually ends up with open-coded
> double loop. With for_each_numa_cpu() it shouldn't be a brainteaser.
> Consider the NUMA-ignorant example:
>
>         cpumask_t cpus = get_mask();
>         int cnt = 0, cpu;
>
>         for_each_cpu(cpu, cpus) {
>                 if (cnt++ == max_num)
>                         break;
>                 do_something(cpu);
>         }
>
> Converting it to NUMA-aware version would be as simple as:
>
>         cpumask_t cpus = get_mask();
>         int node = get_node();
>         int cnt = 0, hop, cpu;
>
>         for_each_numa_cpu(cpu, hop, node, cpus) {
>                 if (cnt++ == max_num)
>                         break;
>                 do_something(cpu);
>         }
>
> The latter looks more verbose and avoids from open-coding that annoying
> double loop. Another advantage is that it works with a 'hop' parameter with
> the clear meaning of NUMA distance, and doesn't make people not familiar
> to enumerator internals bothering with current and previous masks machinery.
>

LGTM, I ran the tests on a few NUMA topologies and that all seems to behave
as expected. Thanks for working on this! 

Reviewed-by: Valentin Schneider <vschneid@redhat.com>

Re: [PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Yury Norov]

> LGTM, I ran the tests on a few NUMA topologies and that all seems to behave
> as expected. Thanks for working on this!
>
> Reviewed-by: Valentin Schneider <vschneid@redhat.com>

Thank you Valentin. If you spent time testing the series, why
don't you add your Tested-by?

Re: [PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Valentin Schneider]

On 02/05/23 14:58, Yury Norov wrote:
>> LGTM, I ran the tests on a few NUMA topologies and that all seems to behave
>> as expected. Thanks for working on this!
>>
>> Reviewed-by: Valentin Schneider <vschneid@redhat.com>
>
> Thank you Valentin. If you spent time testing the series, why
> don't you add your Tested-by?

Well, I only ran the test_bitmap stuff and checked the output of the
iterator then, I didn't get to test on actual hardware with a mellanox card
:-)

But yeah, I suppose that does count for the rest, so feel free to add to
all patches but #5:

Tested-by: Valentin Schneider <vschneid@redhat.com>

Re: [PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Yury Norov]

On Sun, Apr 30, 2023 at 10:18:01AM -0700, Yury Norov wrote:
> for_each_cpu() is widely used in kernel, and it's beneficial to create
> a NUMA-aware version of the macro.
> 
> Recently added for_each_numa_hop_mask() works, but switching existing
> codebase to it is not an easy process.
> 
> This series adds for_each_numa_cpu(), which is designed to be similar to
> the for_each_cpu(). It allows to convert existing code to NUMA-aware as
> simple as adding a hop iterator variable and passing it inside new macro.
> for_each_numa_cpu() takes care of the rest.

Hi Jakub,

Now that the series reviewed, can you consider taking it in sched
tree?

Thanks,
Yury

Re: [PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Jakub Kicinski]

On Wed, 31 May 2023 08:43:46 -0700 Yury Norov wrote:
> On Sun, Apr 30, 2023 at 10:18:01AM -0700, Yury Norov wrote:
> > for_each_cpu() is widely used in kernel, and it's beneficial to create
> > a NUMA-aware version of the macro.
> > 
> > Recently added for_each_numa_hop_mask() works, but switching existing
> > codebase to it is not an easy process.
> > 
> > This series adds for_each_numa_cpu(), which is designed to be similar to
> > the for_each_cpu(). It allows to convert existing code to NUMA-aware as
> > simple as adding a hop iterator variable and passing it inside new macro.
> > for_each_numa_cpu() takes care of the rest.  
> 
> Hi Jakub,
> 
> Now that the series reviewed, can you consider taking it in sched
> tree?

Do you mean someone else or did you mean the net-next tree?

Re: [PATCH v2 0/8] sched/topology: add for_each_numa_cpu() macro

[Yury Norov]

On Wed, May 31, 2023 at 10:01:25AM -0700, Jakub Kicinski wrote:
> On Wed, 31 May 2023 08:43:46 -0700 Yury Norov wrote:
> > On Sun, Apr 30, 2023 at 10:18:01AM -0700, Yury Norov wrote:
> > > for_each_cpu() is widely used in kernel, and it's beneficial to create
> > > a NUMA-aware version of the macro.
> > > 
> > > Recently added for_each_numa_hop_mask() works, but switching existing
> > > codebase to it is not an easy process.
> > > 
> > > This series adds for_each_numa_cpu(), which is designed to be similar to
> > > the for_each_cpu(). It allows to convert existing code to NUMA-aware as
> > > simple as adding a hop iterator variable and passing it inside new macro.
> > > for_each_numa_cpu() takes care of the rest.  
> > 
> > Hi Jakub,
> > 
> > Now that the series reviewed, can you consider taking it in sched
> > tree?
> 
> Do you mean someone else or did you mean the net-next tree?

Sorry, net-next.