| Message ID | 20220817175812.671843-3-vschneid@redhat.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | sched, net: NUMA-aware CPU spreading interface | expand |
On Wed, Aug 17, 2022 at 06:58:09PM +0100, Valentin Schneider wrote: > for_each_cpu_and() is very convenient as it saves having to allocate a > temporary cpumask to store the result of cpumask_and(). The same issue > applies to cpumask_andnot() which doesn't actually need temporary storage > for iteration purposes. > > Following what has been done for for_each_cpu_and(), introduce > for_each_cpu_andnot(). > > Signed-off-by: Valentin Schneider <vschneid@redhat.com> I'm concerned that this series doesn't give us real examples and tests for the new API. If we take it as-is, we'll end up with a dead code for a while, quite probably for long. Can you please submit a new code with a real application for the new API? Alternatively, you can rework some existing code. Briefly grepping, I found good candidate in a core code: __sched_core_flip(), and one candidate in arch code: arch/powerpc/kernel/smp.c: update_coregroup_mask. I believe there are much more. Regarding the test, I don't think it's strictly necessary to have it as soon as we'll have real users, but it's always good to backup with tests. Thanks, Yury
On 18/08/22 15:38, Yury Norov wrote: > On Wed, Aug 17, 2022 at 06:58:09PM +0100, Valentin Schneider wrote: >> for_each_cpu_and() is very convenient as it saves having to allocate a >> temporary cpumask to store the result of cpumask_and(). The same issue >> applies to cpumask_andnot() which doesn't actually need temporary storage >> for iteration purposes. >> >> Following what has been done for for_each_cpu_and(), introduce >> for_each_cpu_andnot(). >> >> Signed-off-by: Valentin Schneider <vschneid@redhat.com> > > I'm concerned that this series doesn't give us real examples and tests > for the new API. If we take it as-is, we'll end up with a dead code for > a while, quite probably for long. > Tariq has at least two uses of for_each_numa_hop_cpu() (which uses for_each_cpu_andnot()) in net/mlx5e and net/enic). My plan here is to make sure the cpumask and sched/topology changes are OK, and then I'd let Tariq carry the whole set with actual users on top. I wouldn't want to see this merged without users, especially given the EXPORT_SYMBOL_GPL() in 3/5. > Can you please submit a new code with a real application for the new API? > Alternatively, you can rework some existing code. > > Briefly grepping, I found good candidate in a core code: __sched_core_flip(), > and one candidate in arch code: arch/powerpc/kernel/smp.c: update_coregroup_mask. > I believe there are much more. > Some of these look fairly trivial, I'll have a look around. > Regarding the test, I don't think it's strictly necessary to have it as soon as > we'll have real users, but it's always good to backup with tests. > That sounds sensible enough, I'll have a look at that. > Thanks, > Yury
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 0d435d0edbcb..295b137717bb 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -237,6 +237,25 @@ unsigned int cpumask_next_and(int n, const struct cpumask *src1p, nr_cpumask_bits, n + 1); } +/** + * cpumask_next_andnot - get the next cpu in *src1p & ~*src2p + * @n: the cpu prior to the place to search (ie. return will be > @n) + * @src1p: the first cpumask pointer + * @src2p: the second cpumask pointer + * + * Returns >= nr_cpu_ids if no further cpus set in *src1p & ~*src2p + */ +static inline +unsigned int cpumask_next_andnot(int n, const struct cpumask *src1p, + const struct cpumask *src2p) +{ + /* -1 is a legal arg here. */ + if (n != -1) + cpumask_check(n); + return find_next_andnot_bit(cpumask_bits(src1p), cpumask_bits(src2p), + nr_cpumask_bits, n + 1); +} + /** * for_each_cpu - iterate over every cpu in a mask * @cpu: the (optionally unsigned) integer iterator @@ -297,6 +316,25 @@ unsigned int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int sta (cpu) = cpumask_next_and((cpu), (mask1), (mask2)), \ (cpu) < nr_cpu_ids;) +/** + * for_each_cpu_andnot - iterate over every cpu in one mask but not in the other + * @cpu: the (optionally unsigned) integer iterator + * @mask1: the first cpumask pointer + * @mask2: the second cpumask pointer + * + * This saves a temporary CPU mask in many places. It is equivalent to: + * struct cpumask tmp; + * cpumask_andnot(&tmp, &mask1, &mask2); + * for_each_cpu(cpu, &tmp) + * ... + * + * After the loop, cpu is >= nr_cpu_ids. + */ +#define for_each_cpu_andnot(cpu, mask1, mask2) \ + for ((cpu) = -1; \ + (cpu) = cpumask_next_andnot((cpu), (mask1), (mask2)), \ + (cpu) < nr_cpu_ids;) + /** * cpumask_any_but - return a "random" in a cpumask, but not this one. * @mask: the cpumask to search
for_each_cpu_and() is very convenient as it saves having to allocate a temporary cpumask to store the result of cpumask_and(). The same issue applies to cpumask_andnot() which doesn't actually need temporary storage for iteration purposes. Following what has been done for for_each_cpu_and(), introduce for_each_cpu_andnot(). Signed-off-by: Valentin Schneider <vschneid@redhat.com> --- include/linux/cpumask.h | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+)