[PATCH] [BLOCK] cfq-iosched: change cfq io context linking from list to tree

On setups with many disks, we spend a considerable amount of time looking up the process-disk mapping on each queue of io. Testing with a NULL based block driver, this costs 40-50% reduction in throughput for 1000 disks.

Jens Axboe committed 20 years ago

Commit e2d74ac1 parent 329b10b3 files · +114 −124Browse files

Showing the changes to include/linux/blkdev.h (1 of 3 files). Show all

Unified · Split

include/linux/blkdev.h+6−8

@@ -55,13 +55,11 @@ struct as_io_context { · 54 unmodified lines
55	55
56	56	struct cfq_queue;
57	57	struct cfq_io_context {
58		− /*
59		− * circular list of cfq_io_contexts belonging to a process io context
60		− */
61		− struct list_head list;
62		− struct cfq_queue *cfqq[2];
	58	+ struct rb_node rb_node;
63	59	void *key;
64	60
	61	+ struct cfq_queue *cfqq[2];
	62	+
65	63	struct io_context *ioc;
66	64
67	65	unsigned long last_end_request;
@@ -72,8 +70,8 @@ struct cfq_io_context { · 4 unmodified lines
72	70
73	71	struct list_head queue_list;
74	72
75		− void (dtor)(struct cfq_io_context );
76		− void (exit)(struct cfq_io_context );
	73	+ void (dtor)(struct io_context ); /* destructor */
	74	+ void (exit)(struct io_context ); /* called on task exit */
77	75	};
78	76
79	77	/*
@@ -94,7 +92,7 @@ struct io_context { · 14 unmodified lines
94	92	int nr_batch_requests; /* Number of requests left in the batch */
95	93
96	94	struct as_io_context *aic;
97		− struct cfq_io_context *cic;
	95	+ struct rb_root cic_root;
98	96	};
99	97
100	98	void put_io_context(struct io_context *ioc);