Currently a threshold for stealing tags from remote CPUs is set to a half of the total number of tags. However, in general case this threshold is a function not only of the total number of tags and maximum number of tags per CPU, but also of a usage pattern. Just let percpu_ida users decide how big this threshold value should be.
Signed-off-by: Alexander Gordeev <[email protected]> --- block/blk-mq-tag.c | 9 +++++---- include/linux/percpu_ida.h | 5 +++-- lib/percpu_ida.c | 7 +++++-- 3 files changed, 13 insertions(+), 8 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index d64a02f..da0b3dd 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -145,10 +145,11 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, tags->nr_max_cache = nr_cache; tags->nr_batch_move = max(1u, nr_cache / 2); - ret = __percpu_ida_init(&tags->free_tags, tags->nr_tags - - tags->nr_reserved_tags, + ret = __percpu_ida_init(&tags->free_tags, + tags->nr_tags - tags->nr_reserved_tags, tags->nr_max_cache, - tags->nr_batch_move); + tags->nr_batch_move, + (tags->nr_tags - tags->nr_reserved_tags) / 2); if (ret) goto err_free_tags; @@ -158,7 +159,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, * no cached. It's fine reserved tags allocation is slow. */ ret = __percpu_ida_init(&tags->reserved_tags, reserved_tags, - 1, 1); + 1, 1, 0); if (ret) goto err_reserved_tags; } diff --git a/include/linux/percpu_ida.h b/include/linux/percpu_ida.h index 1900bd0..d874cca 100644 --- a/include/linux/percpu_ida.h +++ b/include/linux/percpu_ida.h @@ -18,6 +18,7 @@ struct percpu_ida { unsigned nr_tags; unsigned percpu_max_size; unsigned percpu_batch_size; + unsigned max_cached; struct percpu_ida_cpu __percpu *tag_cpu; @@ -66,11 +67,11 @@ void percpu_ida_free(struct percpu_ida *pool, unsigned tag); void percpu_ida_destroy(struct percpu_ida *pool); int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags, - unsigned long max_size, unsigned long batch_size); + unsigned long max_size, unsigned long batch_size, unsigned max_cached); static inline int percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags) { return __percpu_ida_init(pool, nr_tags, IDA_DEFAULT_PCPU_SIZE, - IDA_DEFAULT_PCPU_BATCH_MOVE); + IDA_DEFAULT_PCPU_BATCH_MOVE, nr_tags / 2); } typedef int (*percpu_ida_cb)(unsigned, void *); diff --git a/lib/percpu_ida.c b/lib/percpu_ida.c index 1fc89f9..241f8a3 100644 --- a/lib/percpu_ida.c +++ b/lib/percpu_ida.c @@ -74,7 +74,7 @@ static inline void steal_tags(struct percpu_ida *pool, smp_rmb(); for (cpus_have_tags = cpumask_weight(&pool->cpus_have_tags); - cpus_have_tags * pool->percpu_max_size > pool->nr_tags / 2; + cpus_have_tags * pool->percpu_max_size > pool->max_cached; cpus_have_tags--) { cpu = cpumask_next(cpu, &pool->cpus_have_tags); @@ -294,7 +294,7 @@ EXPORT_SYMBOL_GPL(percpu_ida_destroy); * performance, the workload should not span more cpus than nr_tags / 128. */ int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags, - unsigned long max_size, unsigned long batch_size) + unsigned long max_size, unsigned long batch_size, unsigned max_cached) { unsigned i, cpu, order; @@ -302,6 +302,8 @@ int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags, return -ERANGE; if (!batch_size) return -EINVAL; + if (max_cached > nr_tags) + return -EINVAL; memset(pool, 0, sizeof(*pool)); @@ -310,6 +312,7 @@ int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags, pool->nr_tags = nr_tags; pool->percpu_max_size = max_size; pool->percpu_batch_size = batch_size; + pool->max_cached = max_cached; /* Guard against overflow */ if (nr_tags > (unsigned) INT_MAX + 1) { -- 1.7.7.6 -- Regards, Alexander Gordeev [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
