[PATCH V2] drm/ttm: increase ttm pre-fault value to PMD size

[Zhu Lingshan]

ttm page fault handler ttm_bo_vm_fault_reserved() maps
TTM_BO_VM_NUM_PREFAULT more pages beforehand
due to the principle of locality.

However, on some platform the page faults are more costly, this
patch intends to increase the number of ttm pre-fault to relieve
the number of page faults.

When multiple levels of page table is supported, the new default
value would be the PMD size, similar to huge page.

Signed-off-by: Zhu Lingshan <lingshan.zhu at amd.com>
Reported-and-tested-by: Li Jingxiang <jingxiang.li at ecarxgroup.com>
---
 include/drm/ttm/ttm_bo.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
index 6ccf96c91f3a..ef0f52f56ebc 100644
--- a/include/drm/ttm/ttm_bo.h
+++ b/include/drm/ttm/ttm_bo.h
@@ -39,7 +39,11 @@
 #include "ttm_device.h"
 
 /* Default number of pre-faulted pages in the TTM fault handler */
+#if CONFIG_PGTABLE_LEVELS > 2
+#define TTM_BO_VM_NUM_PREFAULT (1 << (PMD_SHIFT - PAGE_SHIFT))
+#else
 #define TTM_BO_VM_NUM_PREFAULT 16
+#endif
 
 struct iosys_map;
 
-- 
2.45.1