linux-kernel - [patch]block: document blk

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <1311909215.15392.418.camel@sli10-conroe>
Date:	Fri, 29 Jul 2011 11:13:35 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Jens Axboe <jaxboe@...ionio.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: [patch]block: document blk_plug

Andrew Morton is asking to document blk_plug, so here is my attempt.

Signed-off-by: Shaohua Li <shaohua.li@...el.com>
---
 include/linux/blkdev.h |   11 +++++++++++
 1 file changed, 11 insertions(+)

Index: linux/include/linux/blkdev.h
===================================================================
--- linux.orig/include/linux/blkdev.h	2011-07-29 10:51:29.000000000 +0800
+++ linux/include/linux/blkdev.h	2011-07-29 11:07:49.000000000 +0800
@@ -858,6 +858,17 @@ struct request_queue *blk_alloc_queue_no
 extern void blk_put_queue(struct request_queue *);
 
 /*
+ * blk_plug gives each task a request list. Since blk_start_plug() called,
+ * requests from the task will be added to the per-task list and then moved
+ * to global request_queue in a batch way at appropriate time(either
+ * blk_finish_plug() is called or task goes to sleep). blk_plug has some
+ * advantages:
+ * 1. Better request merge. The assumption here is requests from a task have
+ *    better chances to be merged.
+ * 2. Better scalability. Requests are moved from per-task list to global
+ *    request_queue in a batch way, so the total times grabing global
+ *    request_queue lock are reduced.
+ *
  * Note: Code in between changing the blk_plug list/cb_list or element of such
  * lists is preemptable, but such code can't do sleep (or be very careful),
  * otherwise data is corrupted. For details, please check schedule() where


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/