[PATCH] slabify iocontext + request_queue

From: Jens Axboe <axboe@suse.de>

Move both request_queue and io_context allocation to a slab cache.

This is mainly a space-saving exercise.  Some setups have a lot of disks
and the kmalloc rounding-up can consume significant amounts of memory.

diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
index 38d6afa9fc202d253ea424807660acf407e615df..a7bd677b7a66fd7f8ce378059fb601338d57224d 100644 (file)
--- a/drivers/block/ll_rw_blk.c
+++ b/drivers/block/ll_rw_blk.c
@@ -42,6 +42,16 @@ static void blk_unplug_timeout(unsigned long data);
  */
 static kmem_cache_t *request_cachep;
 
+/*
+ * For queue allocation
+ */
+static kmem_cache_t *requestq_cachep;
+
+/*
+ * For io context allocations
+ */
+static kmem_cache_t *iocontext_cachep;
+
 static wait_queue_head_t congestion_wqh[2] = {
                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
@@ -1272,7 +1282,7 @@ void blk_cleanup_queue(request_queue_t * q)
        if (blk_queue_tagged(q))
                blk_queue_free_tags(q);
 
-       kfree(q);
+       kmem_cache_free(requestq_cachep, q);
 }
 
 EXPORT_SYMBOL(blk_cleanup_queue);
@@ -1336,7 +1346,7 @@ __setup("elevator=", elevator_setup);
 
 request_queue_t *blk_alloc_queue(int gfp_mask)
 {
-       request_queue_t *q = kmalloc(sizeof(*q), gfp_mask);
+       request_queue_t *q = kmem_cache_alloc(requestq_cachep, gfp_mask);
 
        if (!q)
                return NULL;
@@ -1425,7 +1435,7 @@ request_queue_t *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
 out_elv:
        blk_cleanup_queue(q);
 out_init:
-       kfree(q);
+       kmem_cache_free(requestq_cachep, q);
        return NULL;
 }
 
@@ -2817,6 +2827,16 @@ int __init blk_dev_init(void)
        if (!request_cachep)
                panic("Can't create request pool slab cache\n");
 
+       requestq_cachep = kmem_cache_create("blkdev_queue",
+                       sizeof(request_queue_t), 0, 0, NULL, NULL);
+       if (!requestq_cachep)
+               panic("Can't create request queue slab cache\n");
+
+       iocontext_cachep = kmem_cache_create("blkdev_ioc",
+                       sizeof(struct io_context), 0, 0, NULL, NULL);
+       if (!iocontext_cachep)
+               panic("Can't create io context slab cache\n");
+
        blk_max_low_pfn = max_low_pfn;
        blk_max_pfn = max_pfn;
        return 0;
@@ -2835,7 +2855,7 @@ void put_io_context(struct io_context *ioc)
        if (atomic_dec_and_test(&ioc->refcount)) {
                if (ioc->aic && ioc->aic->dtor)
                        ioc->aic->dtor(ioc->aic);
-               kfree(ioc);
+               kmem_cache_free(iocontext_cachep, ioc);
        }
 }
 
@@ -2874,7 +2894,7 @@ struct io_context *get_io_context(int gfp_flags)
        local_irq_save(flags);
        ret = tsk->io_context;
        if (ret == NULL) {
-               ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
+               ret = kmem_cache_alloc(iocontext_cachep, GFP_ATOMIC);
                if (ret) {
                        atomic_set(&ret->refcount, 1);
                        ret->pid = tsk->pid;