From mboxrd@z Thu Jan 1 00:00:00 1970 From: gpiccoli@linux.vnet.ibm.com (Guilherme G. Piccoli) Date: Tue, 14 Jun 2016 18:54:22 -0300 Subject: [PATCH 06/13] irq: add a helper spread an affinity mask for MSI/MSI-X vectors In-Reply-To: <1465934346-20648-7-git-send-email-hch@lst.de> References: <1465934346-20648-1-git-send-email-hch@lst.de> <1465934346-20648-7-git-send-email-hch@lst.de> Message-ID: <57607D0E.1060907@linux.vnet.ibm.com> On 06/14/2016 04:58 PM, Christoph Hellwig wrote: > This is lifted from the blk-mq code and adopted to use the affinity mask > concept just intruced in the irq handling code. Very nice patch Christoph, thanks. There's a little typo above, on "intruced". > > Signed-off-by: Christoph Hellwig > --- > include/linux/interrupt.h | 11 +++++++++ > kernel/irq/Makefile | 1 + > kernel/irq/affinity.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 72 insertions(+) > create mode 100644 kernel/irq/affinity.c > > diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h > index 9fcabeb..12003c0 100644 > --- a/include/linux/interrupt.h > +++ b/include/linux/interrupt.h > @@ -278,6 +278,9 @@ extern int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m); > extern int > irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify); > > +int irq_create_affinity_mask(struct cpumask **affinity_mask, > + unsigned int *nr_vecs); > + > #else /* CONFIG_SMP */ > > static inline int irq_set_affinity(unsigned int irq, const struct cpumask *m) > @@ -308,6 +311,14 @@ irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify) > { > return 0; > } > + > +static inline int irq_create_affinity_mask(struct cpumask **affinity_mask, > + unsigned int *nr_vecs) > +{ > + *affinity_mask = NULL; > + *nr_vecs = 1; > + return 0; > +} > #endif /* CONFIG_SMP */ > > /* > diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile > index 2ee42e9..1d3ee31 100644 > --- a/kernel/irq/Makefile > +++ b/kernel/irq/Makefile > @@ -9,3 +9,4 @@ obj-$(CONFIG_GENERIC_IRQ_MIGRATION) += cpuhotplug.o > obj-$(CONFIG_PM_SLEEP) += pm.o > obj-$(CONFIG_GENERIC_MSI_IRQ) += msi.o > obj-$(CONFIG_GENERIC_IRQ_IPI) += ipi.o > +obj-$(CONFIG_SMP) += affinity.o > diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c > new file mode 100644 > index 0000000..1daf8fb > --- /dev/null > +++ b/kernel/irq/affinity.c > @@ -0,0 +1,60 @@ > + > +#include > +#include > +#include > +#include > + > +static int get_first_sibling(unsigned int cpu) > +{ > + unsigned int ret; > + > + ret = cpumask_first(topology_sibling_cpumask(cpu)); > + if (ret < nr_cpu_ids) > + return ret; > + return cpu; > +} > + > +/* > + * Take a map of online CPUs and the number of available interrupt vectors > + * and generate an output cpumask suitable for spreading MSI/MSI-X vectors > + * so that they are distributed as good as possible around the CPUs. If > + * more vectors than CPUs are available we'll map one to each CPU, > + * otherwise we map one to the first sibling of each socket. > + * > + * If there are more vectors than CPUs we will still only have one bit > + * set per CPU, but interrupt code will keep on assining the vectors from > + * the start of the bitmap until we run out of vectors. > + */ Another little typo above in "assining". I take this opportunity to ask you something, since I'm working in a related code in a specific driver - sorry in advance if my question is silly or if I misunderstood your code. The function irq_create_affinity_mask() below deals with the case in which we have nr_vecs < num_online_cpus(); in this case, wouldn't be a good idea to trying distribute the vecs among cores? Example: if we have 128 online cpus, 8 per core (meaning 16 cores) and 64 vecs, I guess would be ideal to distribute 4 vecs _per core_, leaving 4 CPUs in each core without vecs. Makes sense for you? Thanks, Guilherme > +int irq_create_affinity_mask(struct cpumask **affinity_mask, > + unsigned int *nr_vecs) > +{ > + unsigned int vecs = 0; > + > + if (*nr_vecs == 1) { > + *affinity_mask = NULL; > + return 0; > + } > + > + *affinity_mask = kzalloc(cpumask_size(), GFP_KERNEL); > + if (!*affinity_mask) > + return -ENOMEM; > + > + if (*nr_vecs >= num_online_cpus()) { > + cpumask_copy(*affinity_mask, cpu_online_mask); > + } else { > + unsigned int cpu; > + > + for_each_online_cpu(cpu) { > + if (cpu == get_first_sibling(cpu)) { > + cpumask_set_cpu(cpu, *affinity_mask); > + vecs++; > + } > + > + if (--(*nr_vecs) == 0) > + break; > + } > + } > + > + *nr_vecs = vecs; > + return 0; > +} >