linux-kernel - [PATCH v4 6/9] gpu/drm/radeon: optimize out the case when a range is updated to read only

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Message-Id: <20190123222315.1122-7-jglisse@redhat.com>
Date:   Wed, 23 Jan 2019 17:23:12 -0500
From:   jglisse@...hat.com
To:     linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Jérôme Glisse <jglisse@...hat.com>,
        Christian König <christian.koenig@....com>,
        Jan Kara <jack@...e.cz>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Ross Zwisler <zwisler@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Ralph Campbell <rcampbell@...dia.com>,
        John Hubbard <jhubbard@...dia.com>, kvm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: [PATCH v4 6/9] gpu/drm/radeon: optimize out the case when a range is updated to read only

From: Jérôme Glisse <jglisse@...hat.com>

When range of virtual address is updated read only and corresponding
user ptr object are already read only it is pointless to do anything.
Optimize this case out.

Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
Cc: Christian König <christian.koenig@....com>
Cc: Jan Kara <jack@...e.cz>
Cc: Felix Kuehling <Felix.Kuehling@....com>
Cc: Jason Gunthorpe <jgg@...lanox.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Matthew Wilcox <mawilcox@...rosoft.com>
Cc: Ross Zwisler <zwisler@...nel.org>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Cc: Michal Hocko <mhocko@...nel.org>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: John Hubbard <jhubbard@...dia.com>
Cc: kvm@...r.kernel.org
Cc: dri-devel@...ts.freedesktop.org
Cc: linux-rdma@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org
Cc: Arnd Bergmann <arnd@...db.de>
---
 drivers/gpu/drm/radeon/radeon_mn.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_mn.c b/drivers/gpu/drm/radeon/radeon_mn.c
index b3019505065a..f77294f58e63 100644
--- a/drivers/gpu/drm/radeon/radeon_mn.c
+++ b/drivers/gpu/drm/radeon/radeon_mn.c
@@ -124,6 +124,7 @@ static int radeon_mn_invalidate_range_start(struct mmu_notifier *mn,
 	struct radeon_mn *rmn = container_of(mn, struct radeon_mn, mn);
 	struct ttm_operation_ctx ctx = { false, false };
 	struct interval_tree_node *it;
+	bool update_to_read_only;
 	unsigned long end;
 	int ret = 0;
 
@@ -138,6 +139,8 @@ static int radeon_mn_invalidate_range_start(struct mmu_notifier *mn,
 	else if (!mutex_trylock(&rmn->lock))
 		return -EAGAIN;
 
+	update_to_read_only = mmu_notifier_range_update_to_read_only(range);
+
 	it = interval_tree_iter_first(&rmn->objects, range->start, end);
 	while (it) {
 		struct radeon_mn_node *node;
@@ -153,10 +156,20 @@ static int radeon_mn_invalidate_range_start(struct mmu_notifier *mn,
 		it = interval_tree_iter_next(it, range->start, end);
 
 		list_for_each_entry(bo, &node->bos, mn_list) {
+			bool read_only;
 
 			if (!bo->tbo.ttm || bo->tbo.ttm->state != tt_bound)
 				continue;
 
+			/*
+			 * If it is already read only and we are updating to
+			 * read only then we do not need to change anything.
+			 * So save time and skip this one.
+			 */
+			read_only = radeon_ttm_tt_is_readonly(bo->tbo.ttm);
+			if (update_to_read_only && read_only)
+				continue;
+
 			r = radeon_bo_reserve(bo, true);
 			if (r) {
 				DRM_ERROR("(%ld) failed to reserve user bo\n", r);
-- 
2.17.2