# \[PATCH v3 3/3\] ipc/sem: remove obsolete SEMOPM fragmentation warning

- From: Yingjie Wang \<hidden\>
- Date: 2026-10-24 12:21:45 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2026/10/17798050
- Thread: https://ratatoskr.run/linux-mm/2026/10/17798051/t.md

```text
The UAPI comment advises keeping SEMOPM at or below 1000 because a larger
operation array may fail due to physical memory fragmentation.

Commit e4243b8062c1 ("ipc/sem: play nicer with large nsops allocations")
changed the operation array to kvmalloc() specifically to support larger
configured limits, with vmalloc fallback when a physically contiguous
allocation is unavailable.

Replace the obsolete warning with a description of the compiled-in
default and the runtime sysctl.

Signed-off-by: Yingjie Wang <redacted>
Reviewed-by: Manfred Spraul <manfred@colorfullife.com>
---
 include/uapi/linux/sem.h | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h
index 75aa3b273cd99..d9f961a1592c7 100644
--- a/include/uapi/linux/sem.h
+++ b/include/uapi/linux/sem.h
@@ -71,16 +71,15 @@ struct  seminfo {
  * The values has been chosen to be larger than necessary for any
  * known configuration.
  *
- * SEMOPM should not be increased beyond 1000, otherwise there is the
- * risk that semop()/semtimedop() fails due to kernel memory fragmentation when
- * allocating the sop array.
+ * SEMOPM is the default maximum number of operations per semop() call. The
+ * runtime limit can be changed through /proc/sys/kernel/sem.
  */
 
 
 #define SEMMNI  32000           /* <= IPCMNI  max # of semaphore identifiers */
 #define SEMMSL  32000           /* <= INT_MAX max num of semaphores per id */
 #define SEMMNS  (SEMMNI*SEMMSL) /* <= INT_MAX max # of semaphores in system */
-#define SEMOPM  500	        /* <= 1 000 max num of ops per semop call */
+#define SEMOPM  500	        /* <= INT_MAX max num of ops per semop call */
 #define SEMVMX  32767           /* <= 32767 semaphore maximum value */
 #define SEMAEM  SEMVMX          /* adjust on exit max value */
 
-- 
2.43.0

```