From c7c22e4d5c1fdebfac4dba76de7d0338c2b0d832 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Sat, 13 Sep 2008 20:26:01 +0200 Subject: block: add support for IO CPU affinity This patch adds support for controlling the IO completion CPU of either all requests on a queue, or on a per-request basis. We export a sysfs variable (rq_affinity) which, if set, migrates completions of requests to the CPU that originally submitted it. A bio helper (bio_set_completion_cpu()) is also added, so that queuers can ask for completion on that specific CPU. In testing, this has been show to cut the system time by as much as 20-40% on synthetic workloads where CPU affinity is desired. This requires a little help from the architecture, so it'll only work as designed for archs that are using the new generic smp helper infrastructure. Signed-off-by: Jens Axboe --- block/blk.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'block/blk.h') diff --git a/block/blk.h b/block/blk.h index c79f30e1df5..de74254cb91 100644 --- a/block/blk.h +++ b/block/blk.h @@ -59,4 +59,16 @@ static inline int queue_congestion_off_threshold(struct request_queue *q) #endif /* BLK_DEV_INTEGRITY */ +static inline int blk_cpu_to_group(int cpu) +{ +#ifdef CONFIG_SCHED_MC + cpumask_t mask = cpu_coregroup_map(cpu); + return first_cpu(mask); +#elif defined(CONFIG_SCHED_SMT) + return first_cpu(per_cpu(cpu_sibling_map, cpu)); +#else + return cpu; +#endif +} + #endif -- cgit v1.2.3-18-g5258