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authorJens Axboe <axboe@fb.com>2014-05-28 10:15:41 -0600
committerJens Axboe <axboe@fb.com>2014-05-28 10:15:41 -0600
commit75bb4625bb78d6a2d879dcb6a7d482861295765b (patch)
tree0feeef45e4b0fca3c02cf11e13a54d4607535e1a /block/blk-mq-tag.c
parentd852564f8c88b0604490234fdeeb6fb47e4bcc7a (diff)
downloadkernel-75bb4625bb78d6a2d879dcb6a7d482861295765b.tar.gz
blk-mq: add file comments and update copyright notices
None of the blk-mq files have an explanatory comment at the top for what that particular file does. Add that and add appropriate copyright notices as well. Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-mq-tag.c')
-rw-r--r--block/blk-mq-tag.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 0d0640d38a06..d90c4aeb7dd3 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -1,3 +1,15 @@
+/*
+ * Fast and scalable bitmap tagging variant. Uses sparser bitmaps spread
+ * over multiple cachelines to avoid ping-pong between multiple submitters
+ * or submitter and completer. Uses rolling wakeups to avoid falling of
+ * the scaling cliff when we run out of tags and have to start putting
+ * submitters to sleep.
+ *
+ * Uses active queue tracking to support fairer distribution of tags
+ * between multiple submitters when a shared tag map is used.
+ *
+ * Copyright (C) 2013-2014 Jens Axboe
+ */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/random.h>