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author | Kent Overstreet <koverstreet@google.com> | 2013-04-26 10:58:39 +1000 |
---|---|---|
committer | Benjamin LaHaise <bcrl@kvack.org> | 2013-07-30 11:53:11 -0400 |
commit | 34e83fc618085e00dc9803286c581f51966673bd (patch) | |
tree | 9c5054b4b9fc6946765f7d61a8eb47885ef2a424 | |
parent | 0c45355fc7c48c82db151bf0e7ca305d513e639e (diff) | |
download | op-kernel-dev-34e83fc618085e00dc9803286c581f51966673bd.zip op-kernel-dev-34e83fc618085e00dc9803286c581f51966673bd.tar.gz |
aio: reqs_active -> reqs_available
The number of outstanding kiocbs is one of the few shared things left that
has to be touched for every kiocb - it'd be nice to make it percpu.
We can make it per cpu by treating it like an allocation problem: we have
a maximum number of kiocbs that can be outstanding (i.e. slots) - then we
just allocate and free slots, and we know how to write per cpu allocators.
So as prep work for that, we convert reqs_active to reqs_available.
Signed-off-by: Kent Overstreet <koverstreet@google.com>
Cc: Zach Brown <zab@redhat.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Selvan Mani <smani@micron.com>
Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
-rw-r--r-- | fs/aio.c | 38 |
1 files changed, 22 insertions, 16 deletions
@@ -94,7 +94,13 @@ struct kioctx { struct work_struct rcu_work; struct { - atomic_t reqs_active; + /* + * This counts the number of available slots in the ringbuffer, + * so we avoid overflowing it: it's decremented (if positive) + * when allocating a kiocb and incremented when the resulting + * io_event is pulled off the ringbuffer. + */ + atomic_t reqs_available; } ____cacheline_aligned_in_smp; struct { @@ -404,19 +410,20 @@ static void free_ioctx(struct kioctx *ctx) head = ring->head; kunmap_atomic(ring); - while (atomic_read(&ctx->reqs_active) > 0) { + while (atomic_read(&ctx->reqs_available) < ctx->nr_events - 1) { wait_event(ctx->wait, - head != ctx->tail || - atomic_read(&ctx->reqs_active) <= 0); + (head != ctx->tail) || + (atomic_read(&ctx->reqs_available) >= + ctx->nr_events - 1)); avail = (head <= ctx->tail ? ctx->tail : ctx->nr_events) - head; - atomic_sub(avail, &ctx->reqs_active); + atomic_add(avail, &ctx->reqs_available); head += avail; head %= ctx->nr_events; } - WARN_ON(atomic_read(&ctx->reqs_active) < 0); + WARN_ON(atomic_read(&ctx->reqs_available) > ctx->nr_events - 1); aio_free_ring(ctx); @@ -475,6 +482,8 @@ static struct kioctx *ioctx_alloc(unsigned nr_events) if (aio_setup_ring(ctx) < 0) goto out_freectx; + atomic_set(&ctx->reqs_available, ctx->nr_events - 1); + /* limit the number of system wide aios */ spin_lock(&aio_nr_lock); if (aio_nr + nr_events > aio_max_nr || @@ -586,7 +595,7 @@ void exit_aio(struct mm_struct *mm) "exit_aio:ioctx still alive: %d %d %d\n", atomic_read(&ctx->users), atomic_read(&ctx->dead), - atomic_read(&ctx->reqs_active)); + atomic_read(&ctx->reqs_available)); /* * We don't need to bother with munmap() here - * exit_mmap(mm) is coming and it'll unmap everything. @@ -615,12 +624,9 @@ static inline struct kiocb *aio_get_req(struct kioctx *ctx) { struct kiocb *req; - if (atomic_read(&ctx->reqs_active) >= ctx->nr_events) + if (atomic_dec_if_positive(&ctx->reqs_available) <= 0) return NULL; - if (atomic_inc_return(&ctx->reqs_active) > ctx->nr_events - 1) - goto out_put; - req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO); if (unlikely(!req)) goto out_put; @@ -630,7 +636,7 @@ static inline struct kiocb *aio_get_req(struct kioctx *ctx) return req; out_put: - atomic_dec(&ctx->reqs_active); + atomic_inc(&ctx->reqs_available); return NULL; } @@ -701,7 +707,7 @@ void aio_complete(struct kiocb *iocb, long res, long res2) /* * Take rcu_read_lock() in case the kioctx is being destroyed, as we - * need to issue a wakeup after decrementing reqs_active. + * need to issue a wakeup after incrementing reqs_available. */ rcu_read_lock(); @@ -719,7 +725,7 @@ void aio_complete(struct kiocb *iocb, long res, long res2) */ if (unlikely(xchg(&iocb->ki_cancel, KIOCB_CANCELLED) == KIOCB_CANCELLED)) { - atomic_dec(&ctx->reqs_active); + atomic_inc(&ctx->reqs_available); /* Still need the wake_up in case free_ioctx is waiting */ goto put_rq; } @@ -857,7 +863,7 @@ static long aio_read_events_ring(struct kioctx *ctx, pr_debug("%li h%u t%u\n", ret, head, ctx->tail); - atomic_sub(ret, &ctx->reqs_active); + atomic_add(ret, &ctx->reqs_available); out: mutex_unlock(&ctx->ring_lock); @@ -1241,7 +1247,7 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, aio_put_req(req); /* drop extra ref to req */ return 0; out_put_req: - atomic_dec(&ctx->reqs_active); + atomic_inc(&ctx->reqs_available); aio_put_req(req); /* drop extra ref to req */ aio_put_req(req); /* drop i/o ref to req */ return ret; |