Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755795Ab3ENBTM (ORCPT ); Mon, 13 May 2013 21:19:12 -0400 Received: from mail-pa0-f51.google.com ([209.85.220.51]:39390 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755656Ab3ENBTH (ORCPT ); Mon, 13 May 2013 21:19:07 -0400 From: Kent Overstreet To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org Cc: akpm@linux-foundation.org, Kent Overstreet , Zach Brown , Felipe Balbi , Greg Kroah-Hartman , Mark Fasheh , Joel Becker , Rusty Russell , Jens Axboe , Asai Thambi S P , Selvan Mani , Sam Bradshaw , Jeff Moyer , Al Viro , Benjamin LaHaise Subject: [PATCH 02/21] aio: reqs_active -> reqs_available Date: Mon, 13 May 2013 18:18:39 -0700 Message-Id: <1368494338-7069-3-git-send-email-koverstreet@google.com> X-Mailer: git-send-email 1.8.2.1 In-Reply-To: <1368494338-7069-1-git-send-email-koverstreet@google.com> References: <1368494338-7069-1-git-send-email-koverstreet@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5227 Lines: 157 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 Cc: Zach Brown Cc: Felipe Balbi Cc: Greg Kroah-Hartman Cc: Mark Fasheh Cc: Joel Becker Cc: Rusty Russell Cc: Jens Axboe Cc: Asai Thambi S P Cc: Selvan Mani Cc: Sam Bradshaw Cc: Jeff Moyer Cc: Al Viro Cc: Benjamin LaHaise Reviewed-by: "Theodore Ts'o" Signed-off-by: Andrew Morton --- fs/aio.c | 35 ++++++++++++++++++++--------------- 1 file changed, 20 insertions(+), 15 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index fe794af..bde41c1 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -89,7 +89,13 @@ 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 { @@ -306,19 +312,19 @@ 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); + (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); @@ -382,6 +388,8 @@ 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 || @@ -484,7 +492,7 @@ 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. @@ -516,12 +524,9 @@ 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; @@ -531,7 +536,7 @@ 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; } @@ -602,7 +607,7 @@ 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(); @@ -620,7 +625,7 @@ 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; } @@ -758,7 +763,7 @@ 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); @@ -1142,7 +1147,7 @@ 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; -- 1.8.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/