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| author | Tejun Heo <tj@kernel.org> | 2015-08-19 00:55:20 +0300 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2015-08-19 01:49:17 +0300 |
| commit | ae11889636111199dbcf47283b4167f578b69472 (patch) | |
| tree | 02870926926c7391d41e4b40a8b5bcf82ce34aab /block/blk-cgroup.c | |
| parent | c9589f03e490956628ff91a1da133216dc796b63 (diff) | |
| download | linux-ae11889636111199dbcf47283b4167f578b69472.tar.xz | |
blkcg: consolidate blkg creation in blkcg_bio_issue_check()
blkg (blkcg_gq) currently is created by blkcg policies invoking
blkg_lookup_create() which ends up repeating about the same code in
different policies. Theoretically, this can avoid the overhead of
looking and/or creating blkg's if blkcg is enabled but no policy is in
use; however, the cost of blkg lookup / creation is very low
especially if only the root blkcg is in use which is highly likely if
no blkcg policy is in active use - it boils down to a single very
predictable conditional and surrounding RCU protection.
This patch consolidates blkg creation to a new function
blkcg_bio_issue_check() which is called during bio issue from
generic_make_request_checks(). blkcg_bio_issue_check() is now the
only function which tries to create missing blkg's. The subsequent
policy and request_list operations just perform blkg_lookup() and if
missing falls back to the root.
* blk_get_rl() no longer tries to create blkg. It uses blkg_lookup()
instead of blkg_lookup_create().
* blk_throtl_bio() is now called from blkcg_bio_issue_check() with rcu
read locked and blkg already looked up. Both throtl_lookup_tg() and
throtl_lookup_create_tg() are dropped.
* cfq is similarly updated. cfq_lookup_create_cfqg() is replaced with
cfq_lookup_cfqg()which uses blkg_lookup().
This consolidates blkg handling and avoids unnecessary blkg creation
retries under memory pressure. In addition, this provides a common
bio entry point into blkcg where things like common accounting can be
performed.
v2: Build fixes for !CONFIG_CFQ_GROUP_IOSCHED and
!CONFIG_BLK_DEV_THROTTLING.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-cgroup.c')
| -rw-r--r-- | block/blk-cgroup.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 52e637ed9d7e..097c4a670fa4 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -153,6 +153,7 @@ struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg, return NULL; } +EXPORT_SYMBOL_GPL(blkg_lookup_slowpath); /* * If @new_blkg is %NULL, this function tries to allocate a new one as @@ -295,7 +296,6 @@ struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, return blkg; } } -EXPORT_SYMBOL_GPL(blkg_lookup_create); static void blkg_destroy(struct blkcg_gq *blkg) { |