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authorDavid Rientjes <rientjes@google.com>2009-06-16 15:32:56 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:43 -0700
commit2ff05b2b4eac2e63d345fc731ea151a060247f53 (patch)
tree1840bc2d3b381eca5d39869499339b0fcc6eabbf /include/linux
parentc9e444103b5e7a5a3519f9913f59767f92e33baf (diff)
oom: move oom_adj value from task_struct to mm_struct
The per-task oom_adj value is a characteristic of its mm more than the task itself since it's not possible to oom kill any thread that shares the mm. If a task were to be killed while attached to an mm that could not be freed because another thread were set to OOM_DISABLE, it would have needlessly been terminated since there is no potential for future memory freeing. This patch moves oomkilladj (now more appropriately named oom_adj) from struct task_struct to struct mm_struct. This requires task_lock() on a task to check its oom_adj value to protect against exec, but it's already necessary to take the lock when dereferencing the mm to find the total VM size for the badness heuristic. This fixes a livelock if the oom killer chooses a task and another thread sharing the same memory has an oom_adj value of OOM_DISABLE. This occurs because oom_kill_task() repeatedly returns 1 and refuses to kill the chosen task while select_bad_process() will repeatedly choose the same task during the next retry. Taking task_lock() in select_bad_process() to check for OOM_DISABLE and in oom_kill_task() to check for threads sharing the same memory will be removed in the next patch in this series where it will no longer be necessary. Writing to /proc/pid/oom_adj for a kthread will now return -EINVAL since these threads are immune from oom killing already. They simply report an oom_adj value of OOM_DISABLE. Cc: Nick Piggin <npiggin@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/mm_types.h2
-rw-r--r--include/linux/sched.h1
2 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 0e80e26ecf2..f4408106fcb 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -232,6 +232,8 @@ struct mm_struct {
unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
+ s8 oom_adj; /* OOM kill score adjustment (bit shift) */
+
cpumask_t cpu_vm_mask;
/* Architecture-specific MM context */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1048bf50540..1bc6fae0c13 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1178,7 +1178,6 @@ struct task_struct {
* a short time
*/
unsigned char fpu_counter;
- s8 oomkilladj; /* OOM kill score adjustment (bit shift). */
#ifdef CONFIG_BLK_DEV_IO_TRACE
unsigned int btrace_seq;
#endif