linux-kernel - [RFC PATCH 2/2] block: adaptive rq

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

Date:	Fri, 22 Jul 2011 13:59:44 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	jaxboe@...ionio.com
Cc:	Roland Dreier <roland@...estorage.com>,
	Dave Jiang <dave.jiang@...el.com>, linux-scsi@...r.kernel.org,
	Matthew Wilcox <matthew@....cx>, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>
Subject: [RFC PATCH 2/2] block: adaptive rq_affinity

For some storage configurations the coarse grained cpu grouping (socket)
does not supply enough cpu to keep up with the demands of high iops.
Bypass the grouping and complete on the direct requester cpu when the
local cpu is under softirq pressure (as measured by ksoftirqd being in
the running state).

Cc: Matthew Wilcox <matthew@....cx>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Roland Dreier <roland@...estorage.com>
Tested-by: Dave Jiang <dave.jiang@...el.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 block/blk-softirq.c |   12 +++++++++++-
 1 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 475fab8..f0cda19 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -101,16 +101,20 @@ static struct notifier_block __cpuinitdata blk_cpu_notifier = {
 	.notifier_call	= blk_cpu_notify,
 };
 
+DECLARE_PER_CPU(struct task_struct *, ksoftirqd);
+
 void __blk_complete_request(struct request *req)
 {
 	int ccpu, cpu, group_cpu = NR_CPUS;
 	struct request_queue *q = req->q;
+	struct task_struct *tsk;
 	unsigned long flags;
 
 	BUG_ON(!q->softirq_done_fn);
 
 	local_irq_save(flags);
 	cpu = smp_processor_id();
+	tsk = per_cpu(ksoftirqd, cpu);
 
 	/*
 	 * Select completion CPU
@@ -124,7 +128,13 @@ void __blk_complete_request(struct request *req)
 	} else
 		ccpu = cpu;
 
-	if (ccpu == cpu || ccpu == group_cpu) {
+	/*
+	 * try to skip a remote softirq-trigger if the completion is
+	 * within the same group, but not if local softirqs have already
+	 * spilled to ksoftirqd
+	 */
+	if (ccpu == cpu ||
+	    (ccpu == group_cpu && tsk->state != TASK_RUNNING)) {
 		struct list_head *list;
 do_local:
 		list = &__get_cpu_var(blk_cpu_done);

--
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/