ROTATE_BYTES: prevent OOM due to page table size too large

Cases that use ROTATE_BYTES as its unit_size use all the memory as
file backed read only memory and are easily reclaimed; but the memory
consumed by page table is not reclaimable and could cause OOM since
ROTATE_BYTES is pretty large.
Refine ROTATE_BYTES in hw_vars as is done in case-anon-r-rand so that
other test cases will also avoid the OOM issue.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>

3 files changed, 2 insertions, 6 deletions

diff --git a/case-anon-r-rand b/case-anon-r-rand
index f829738..e8ee976 100755
--- a/case-anon-r-rand
+++ b/case-anon-r-rand
@@ -2,7 +2,4 @@
 
 . ./hw_vars
 
-# prevent OOM: limit pagetable pages to half memory
-[ "$ROTATE_BYTES" -gt $(( mem << 8 )) ] && ROTATE_BYTES=$(( mem << 8 ))
-
 $USEMEM -n $nr_task --readonly --random $((ROTATE_BYTES / nr_task))
diff --git a/case-anon-r-rand-mt b/case-anon-r-rand-mt
index 0838756..fa347d6 100755
--- a/case-anon-r-rand-mt
+++ b/case-anon-r-rand-mt
@@ -2,7 +2,4 @@
 
 . ./hw_vars
 
-# prevent OOM: limit pagetable pages to half memory
-[ "$ROTATE_BYTES" -gt $(( mem << 8 )) ] && ROTATE_BYTES=$(( mem << 8 ))
-
 $USEMEM -t $nr_task --readonly --random $((ROTATE_BYTES / nr_task))
diff --git a/hw_vars b/hw_vars
index d47592f..c0fd413 100755
--- a/hw_vars
+++ b/hw_vars
@@ -134,6 +134,8 @@ mem=$((MemTotal << 10))
 hugepagesize=$((Hugepagesize << 10))
 
 ROTATE_BYTES=$((1<<42))
+# prevent OOM: limit pagetable pages to half memory
+[ "$ROTATE_BYTES" -gt $(( mem << 8 )) ] && ROTATE_BYTES=$(( mem << 8 ))
 
 # Documentation/x86/x86_64/mm.txt
 # 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm