From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753541Ab2KEN4e (ORCPT ); Mon, 5 Nov 2012 08:56:34 -0500 Received: from smtp-outbound-1.vmware.com ([208.91.2.12]:54282 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932681Ab2KEN4H (ORCPT ); Mon, 5 Nov 2012 08:56:07 -0500 From: Thomas Hellstrom To: airlied@gmail.com, airlied@redhat.com Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Thomas Hellstrom Subject: [PATCH 4/4] drm/ttm: Optimize reservation slightly Date: Mon, 5 Nov 2012 14:55:44 +0100 Message-Id: <1352123744-13269-5-git-send-email-thellstrom@vmware.com> X-Mailer: git-send-email 1.7.4.4 In-Reply-To: <1352123744-13269-1-git-send-email-thellstrom@vmware.com> References: <1352123744-13269-1-git-send-email-thellstrom@vmware.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Reservation locking currently always takes place under the LRU spinlock. Hence, strictly there is no need for an atomic_cmpxchg call; we can use atomic_read followed by atomic_write since nobody else will ever reserve without the lru spinlock held. At least on Intel this should remove a locked bus cycle on successful reserve. Signed-off-by: Thomas Hellstrom --- drivers/gpu/drm/ttm/ttm_bo.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index bf6e4b5..46008ea 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -220,7 +220,7 @@ int ttm_bo_reserve_locked(struct ttm_buffer_object *bo, struct ttm_bo_global *glob = bo->glob; int ret; - while (unlikely(atomic_cmpxchg(&bo->reserved, 0, 1) != 0)) { + while (unlikely(atomic_read(&bo->reserved) != 0)) { /** * Deadlock avoidance for multi-bo reserving. */ @@ -249,6 +249,7 @@ int ttm_bo_reserve_locked(struct ttm_buffer_object *bo, return ret; } + atomic_set(&bo->reserved, 1); if (use_sequence) { /** * Wake up waiters that may need to recheck for deadlock, -- 1.7.4.4