| Message ID | 541C27F7.1020509@acm.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On 9/19/2014 3:56 PM, Bart Van Assche wrote: > [PATCH 1/8] blk-mq: Use all available hardware queues > > Suppose that a system has two CPU sockets, three cores per socket, > that it does not support hyperthreading and that four hardware > queues are provided by a block driver. With the current algorithm > this will lead to the following assignment of CPU cores to hardware > queues: > > HWQ 0: 0 1 > HWQ 1: 2 3 > HWQ 2: 4 5 > HWQ 3: (none) > > This patch changes the queue assignment into: > > HWQ 0: 0 1 > HWQ 1: 2 > HWQ 2: 3 4 > HWQ 3: 5 > > In other words, this patch has the following three effects: > - All four hardware queues are used instead of only three. > - CPU cores are spread more evenly over hardware queues. For the > above example the range of the number of CPU cores associated > with a single HWQ is reduced from [0..2] to [1..2]. > - If the number of HWQ's is a multiple of the number of CPU sockets > it is now guaranteed that all CPU cores associated with a single > HWQ reside on the same CPU socket. > > Signed-off-by: Bart Van Assche <bvanassche@acm.org> > Cc: Jens Axboe <axboe@fb.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Ming Lei <ming.lei@canonical.com> > --- > block/blk-mq-cpumap.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c > index 1065d7c..8e56455 100644 > --- a/block/blk-mq-cpumap.c > +++ b/block/blk-mq-cpumap.c > @@ -17,7 +17,7 @@ > static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues, > const int cpu) > { > - return cpu / ((nr_cpus + nr_queues - 1) / nr_queues); > + return cpu * nr_queues / nr_cpus; > } > > static int get_first_sibling(unsigned int cpu) > Seems reasonable enough. Reviewed-by: Sagi Grimberg <sagig@mellanox.com> -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c index 1065d7c..8e56455 100644 --- a/block/blk-mq-cpumap.c +++ b/block/blk-mq-cpumap.c @@ -17,7 +17,7 @@ static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues, const int cpu) { - return cpu / ((nr_cpus + nr_queues - 1) / nr_queues); + return cpu * nr_queues / nr_cpus; } static int get_first_sibling(unsigned int cpu)
[PATCH 1/8] blk-mq: Use all available hardware queues Suppose that a system has two CPU sockets, three cores per socket, that it does not support hyperthreading and that four hardware queues are provided by a block driver. With the current algorithm this will lead to the following assignment of CPU cores to hardware queues: HWQ 0: 0 1 HWQ 1: 2 3 HWQ 2: 4 5 HWQ 3: (none) This patch changes the queue assignment into: HWQ 0: 0 1 HWQ 1: 2 HWQ 2: 3 4 HWQ 3: 5 In other words, this patch has the following three effects: - All four hardware queues are used instead of only three. - CPU cores are spread more evenly over hardware queues. For the above example the range of the number of CPU cores associated with a single HWQ is reduced from [0..2] to [1..2]. - If the number of HWQ's is a multiple of the number of CPU sockets it is now guaranteed that all CPU cores associated with a single HWQ reside on the same CPU socket. Signed-off-by: Bart Van Assche <bvanassche@acm.org> Cc: Jens Axboe <axboe@fb.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Ming Lei <ming.lei@canonical.com> --- block/blk-mq-cpumap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)