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authorJeff Moyer <jmoyer@redhat.com>2009-10-02 18:57:36 -0400
committerJens Axboe <jens.axboe@oracle.com>2009-10-28 09:29:25 +0100
commitcfb1e33eed48165763edc7a4a067cf5f74898d0b (patch)
treed0e0bdd0664615b1f7be6cf770476e16dbcad116 /fs/aio.c
parent1af60fbd759d31f565552fea315c2033947cfbe6 (diff)
aio: implement request batching
Hi, Some workloads issue batches of small I/O, and the performance is poor due to the call to blk_run_address_space for every single iocb. Nathan Roberts pointed this out, and suggested that by deferring this call until all I/Os in the iocb array are submitted to the block layer, we can realize some impressive performance gains (up to 30% for sequential 4k reads in batches of 16). Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'fs/aio.c')
-rw-r--r--fs/aio.c61
1 files changed, 59 insertions, 2 deletions
diff --git a/fs/aio.c b/fs/aio.c
index 02a2c934057..cf0bef428f8 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -32,6 +32,9 @@
#include <linux/workqueue.h>
#include <linux/security.h>
#include <linux/eventfd.h>
+#include <linux/blkdev.h>
+#include <linux/mempool.h>
+#include <linux/hash.h>
#include <asm/kmap_types.h>
#include <asm/uaccess.h>
@@ -60,6 +63,14 @@ static DECLARE_WORK(fput_work, aio_fput_routine);
static DEFINE_SPINLOCK(fput_lock);
static LIST_HEAD(fput_head);
+#define AIO_BATCH_HASH_BITS 3 /* allocated on-stack, so don't go crazy */
+#define AIO_BATCH_HASH_SIZE (1 << AIO_BATCH_HASH_BITS)
+struct aio_batch_entry {
+ struct hlist_node list;
+ struct address_space *mapping;
+};
+mempool_t *abe_pool;
+
static void aio_kick_handler(struct work_struct *);
static void aio_queue_work(struct kioctx *);
@@ -73,6 +84,8 @@ static int __init aio_setup(void)
kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
aio_wq = create_workqueue("aio");
+ abe_pool = mempool_create_kmalloc_pool(1, sizeof(struct aio_batch_entry));
+ BUG_ON(!abe_pool);
pr_debug("aio_setup: sizeof(struct page) = %d\n", (int)sizeof(struct page));
@@ -1531,8 +1544,44 @@ static int aio_wake_function(wait_queue_t *wait, unsigned mode,
return 1;
}
+static void aio_batch_add(struct address_space *mapping,
+ struct hlist_head *batch_hash)
+{
+ struct aio_batch_entry *abe;
+ struct hlist_node *pos;
+ unsigned bucket;
+
+ bucket = hash_ptr(mapping, AIO_BATCH_HASH_BITS);
+ hlist_for_each_entry(abe, pos, &batch_hash[bucket], list) {
+ if (abe->mapping == mapping)
+ return;
+ }
+
+ abe = mempool_alloc(abe_pool, GFP_KERNEL);
+ BUG_ON(!igrab(mapping->host));
+ abe->mapping = mapping;
+ hlist_add_head(&abe->list, &batch_hash[bucket]);
+ return;
+}
+
+static void aio_batch_free(struct hlist_head *batch_hash)
+{
+ struct aio_batch_entry *abe;
+ struct hlist_node *pos, *n;
+ int i;
+
+ for (i = 0; i < AIO_BATCH_HASH_SIZE; i++) {
+ hlist_for_each_entry_safe(abe, pos, n, &batch_hash[i], list) {
+ blk_run_address_space(abe->mapping);
+ iput(abe->mapping->host);
+ hlist_del(&abe->list);
+ mempool_free(abe, abe_pool);
+ }
+ }
+}
+
static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
- struct iocb *iocb)
+ struct iocb *iocb, struct hlist_head *batch_hash)
{
struct kiocb *req;
struct file *file;
@@ -1608,6 +1657,12 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
;
}
spin_unlock_irq(&ctx->ctx_lock);
+ if (req->ki_opcode == IOCB_CMD_PREAD ||
+ req->ki_opcode == IOCB_CMD_PREADV ||
+ req->ki_opcode == IOCB_CMD_PWRITE ||
+ req->ki_opcode == IOCB_CMD_PWRITEV)
+ aio_batch_add(file->f_mapping, batch_hash);
+
aio_put_req(req); /* drop extra ref to req */
return 0;
@@ -1635,6 +1690,7 @@ SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
struct kioctx *ctx;
long ret = 0;
int i;
+ struct hlist_head batch_hash[AIO_BATCH_HASH_SIZE] = { { 0, }, };
if (unlikely(nr < 0))
return -EINVAL;
@@ -1666,10 +1722,11 @@ SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
break;
}
- ret = io_submit_one(ctx, user_iocb, &tmp);
+ ret = io_submit_one(ctx, user_iocb, &tmp, batch_hash);
if (ret)
break;
}
+ aio_batch_free(batch_hash);
put_ioctx(ctx);
return i ? i : ret;