[PATCH] drm/i915: Stop reconfiguring our shmemfs mountpoint

* [PATCH] drm/i915: Stop reconfiguring our shmemfs mountpoint
@ 2019-08-08 17:22 Chris Wilson
  2019-08-08 21:56 ` Hugh Dickins
                   ` (2 more replies)
  0 siblings, 3 replies; 7+ messages in thread
From: Chris Wilson @ 2019-08-08 17:22 UTC (permalink / raw)
  To: intel-gfx
  Cc: linux-fsdevel, linux-kernel, Chris Wilson, Sergey Senozhatsky,
	Sedat Dilek, Hugh Dickins, Matthew Auld, Al Viro

The filesystem reconfigure API is undergoing a transition, breaking our
current code. As we only set the default options, we can simply remove
the call to s_op->remount_fs(). In the future, when HW permits, we can
try re-enabling huge page support, albeit as suggested with new per-file
controls.

Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Suggested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 drivers/gpu/drm/i915/gem/i915_gemfs.c | 31 ++++++++-------------------
 1 file changed, 9 insertions(+), 22 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gemfs.c b/drivers/gpu/drm/i915/gem/i915_gemfs.c
index 099f3397aada..be94598cb304 100644
--- a/drivers/gpu/drm/i915/gem/i915_gemfs.c
+++ b/drivers/gpu/drm/i915/gem/i915_gemfs.c
@@ -20,31 +20,18 @@ int i915_gemfs_init(struct drm_i915_private *i915)
 	if (!type)
 		return -ENODEV;
 
-	gemfs = kern_mount(type);
-	if (IS_ERR(gemfs))
-		return PTR_ERR(gemfs);
-
 	/*
-	 * Enable huge-pages for objects that are at least HPAGE_PMD_SIZE, most
-	 * likely 2M. Note that within_size may overallocate huge-pages, if say
-	 * we allocate an object of size 2M + 4K, we may get 2M + 2M, but under
-	 * memory pressure shmem should split any huge-pages which can be
-	 * shrunk.
+	 * By creating our own shmemfs mountpoint, we can pass in
+	 * mount flags that better match our usecase.
+	 *
+	 * One example, although it is probably better with a per-file
+	 * control, is selecting huge page allocations ("huge=within").
+	 * Currently unused due to bandwidth issues (slow reads) on Broadwell+.
 	 */
 
-	if (has_transparent_hugepage()) {
-		struct super_block *sb = gemfs->mnt_sb;
-		/* FIXME: Disabled until we get W/A for read BW issue. */
-		char options[] = "huge=never";
-		int flags = 0;
-		int err;
-
-		err = sb->s_op->remount_fs(sb, &flags, options);
-		if (err) {
-			kern_unmount(gemfs);
-			return err;
-		}
-	}
+	gemfs = kern_mount(type);
+	if (IS_ERR(gemfs))
+		return PTR_ERR(gemfs);
 
 	i915->mm.gemfs = gemfs;
 
-- 
2.23.0.rc1


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