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 --- include/linux/bio.h | 11 +++++++++++ include/linux/blkdev.h | 5 ++++- include/linux/elevator.h | 8 ++++---- 3 files changed, 19 insertions(+), 5 deletions(-) (limited to 'include/linux') diff --git a/include/linux/bio.h b/include/linux/bio.h index 2c0c090..13aba20 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -81,6 +81,8 @@ struct bio { unsigned int bi_max_vecs; /* max bvl_vecs we can hold */ + unsigned int bi_comp_cpu; /* completion CPU */ + struct bio_vec *bi_io_vec; /* the actual vec list */ bio_end_io_t *bi_end_io; @@ -105,6 +107,7 @@ struct bio { #define BIO_BOUNCED 5 /* bio is a bounce bio */ #define BIO_USER_MAPPED 6 /* contains user pages */ #define BIO_EOPNOTSUPP 7 /* not supported */ +#define BIO_CPU_AFFINE 8 /* complete bio on same CPU as submitted */ #define bio_flagged(bio, flag) ((bio)->bi_flags & (1 << (flag))) /* @@ -343,6 +346,14 @@ extern struct bio_vec *bvec_alloc_bs(gfp_t, int, unsigned long *, struct bio_set extern unsigned int bvec_nr_vecs(unsigned short idx); /* + * Allow queuer to specify a completion CPU for this bio + */ +static inline void bio_set_completion_cpu(struct bio *bio, unsigned int cpu) +{ + bio->bi_comp_cpu = cpu; +} + +/* * bio_set is used to allow other portions of the IO system to * allocate their own private memory pools for bio and iovec structures. * These memory pools in turn all allocate from the bio_slab diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 10aa46c..93204bf 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -17,6 +17,7 @@ #include #include #include +#include #include @@ -139,7 +140,8 @@ enum rq_flag_bits { */ struct request { struct list_head queuelist; - struct list_head donelist; + struct call_single_data csd; + int cpu; struct request_queue *q; @@ -420,6 +422,7 @@ struct request_queue #define QUEUE_FLAG_ELVSWITCH 8 /* don't use elevator, just do FIFO */ #define QUEUE_FLAG_BIDI 9 /* queue supports bidi requests */ #define QUEUE_FLAG_NOMERGES 10 /* disable merge attempts */ +#define QUEUE_FLAG_SAME_COMP 11 /* force complete on same CPU */ static inline int queue_is_locked(struct request_queue *q) { diff --git a/include/linux/elevator.h b/include/linux/elevator.h index 639624b..bb791c3 100644 --- a/include/linux/elevator.h +++ b/include/linux/elevator.h @@ -173,15 +173,15 @@ enum { #define rb_entry_rq(node) rb_entry((node), struct request, rb_node) /* - * Hack to reuse the donelist list_head as the fifo time holder while + * Hack to reuse the csd.list list_head as the fifo time holder while * the request is in the io scheduler. Saves an unsigned long in rq. */ -#define rq_fifo_time(rq) ((unsigned long) (rq)->donelist.next) -#define rq_set_fifo_time(rq,exp) ((rq)->donelist.next = (void *) (exp)) +#define rq_fifo_time(rq) ((unsigned long) (rq)->csd.list.next) +#define rq_set_fifo_time(rq,exp) ((rq)->csd.list.next = (void *) (exp)) #define rq_entry_fifo(ptr) list_entry((ptr), struct request, queuelist) #define rq_fifo_clear(rq) do { \ list_del_init(&(rq)->queuelist); \ - INIT_LIST_HEAD(&(rq)->donelist); \ + INIT_LIST_HEAD(&(rq)->csd.list); \ } while (0) /* -- cgit v1.1