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[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

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include/linux/blkdev.h+6−8
@@ -55,13 +55,11 @@ struct as_io_context { · 54 unmodified lines
55 55
56struct cfq_queue;56struct cfq_queue;
57struct cfq_io_context {57struct cfq_io_context {
58 /*58 struct rb_node rb_node;
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];
63 void *key;59 void *key;
64 60
61 struct cfq_queue *cfqq[2];
62
65 struct io_context *ioc;63 struct io_context *ioc;
66 64
67 unsigned long last_end_request;65 unsigned long last_end_request;
@@ -72,8 +70,8 @@ struct cfq_io_context { · 4 unmodified lines
72 70
73 struct list_head queue_list;71 struct list_head queue_list;
74 72
75 void (*dtor)(struct cfq_io_context *);73 void (*dtor)(struct io_context *); /* destructor */
76 void (*exit)(struct cfq_io_context *);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 int nr_batch_requests; /* Number of requests left in the batch */92 int nr_batch_requests; /* Number of requests left in the batch */
95 93
96 struct as_io_context *aic;94 struct as_io_context *aic;
97 struct cfq_io_context *cic;95 struct rb_root cic_root;
98};96};
99 97
100void put_io_context(struct io_context *ioc);98void put_io_context(struct io_context *ioc);