Quoting Gary Ballantyne (gary.ballant...@haulashore.com):
> On Fri, 1 Feb 2013 10:24:13 -0600
> Serge Hallyn <serge.hal...@canonical.com> wrote:
>
> >
> > Did you actually test with a memory hog program? I just noticed there
> > appears to be a bug in that if I
> >
> > d=/sys/fs/cgroup/memory/a
> > mkdir $d
> > echo 1 > $d/memory.use_hierarchy
> > echo 5000 > $d/memory.limit_in_bytes
> > mkdir $d/b
> >
> > then $d/b/memory.limit_in_bytes does not report the reduced limit. However
> > whenI run a program which does char *c = malloc(10000) after doing
> > echo $$ > $d/b/tasks
> >
> > then I get killed by OOM.
> >
> > -serge
>
> I tested with a large array in ipython. Though, from your example, it seems
> I'm missing memory.use_hierarchy.
>
> In principle, it seems like I need something like:
>
> echo 1 > /sys/fs/cgroup/memory/lxc/memory.use_hierarchy
>
> But, I can't do that before the container is started (no lxc directory) or
> after it is started (device busy).
>
Yup, it looks like lxc ought to set that at startup. I can think of
absolutely no cases where we would *not* want that done. Something
like:
Subject: [PATCH 1/1] Try to enable memory cgroup use_hierarchy option.
The memory cgroup has a 'memory.use_hierarchy' which is initialized to
0. It needs to be set to 1 at our top level, that is
/sys/fs/cgroup/memory/lxc/memory.use_hiararchy, before we create any
containers. After the fact is too late.
Signed-off-by: Serge Hallyn <serge.hal...@ubuntu.com>
---
src/lxc/cgroup.c | 41 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 41 insertions(+)
diff --git a/src/lxc/cgroup.c b/src/lxc/cgroup.c
index 28f3474..0078eda 100644
--- a/src/lxc/cgroup.c
+++ b/src/lxc/cgroup.c
@@ -482,6 +482,43 @@ int try_to_move_cgname(char *cgparent, char *cgname)
}
/*
+ * The memory cgroup has a 'memory.use_hierarchy' which is initialized to
+ * 0. It needs to be set to 1 at our top level, that is
+ * /sys/fs/cgroup/memory/lxc/memory.use_hiararchy, before we create any
+ * containers. After the fact is too late.
+ */
+static int enable_hierarchy(char *path)
+{
+ char filepath[MAXPATHLEN];
+ int ret;
+ FILE *f;
+ int len = strlen(path);
+
+ if (strlen(path) < 7 || strcmp(&path[len-6], "memory") != 0)
+ return 0;
+
+ ret = snprintf(filepath, MAXPATHLEN, "%s/memory.use_hierarchy");
+ if (ret < 0 || ret >= MAXPATHLEN) {
+ SYSERROR("Failed creating memory hierarchy filepath name");
+ return -1;
+ }
+
+ f = fopen(filepath, "w");
+ if (!f) {
+ /* kernel may not support this file - s'ok */
+ WARN("Unable to open cgroup memory.use_hierarchy file");
+ return 0;
+ }
+
+ if (fprintf(f, "1") < 1) {
+ WARN("Unable to set hierarchy to true for memory cgroup");
+ }
+ fclose(f);
+
+ return 0;
+}
+
+/*
* create a cgroup for the container in a particular subsystem.
*/
static int lxc_one_cgroup_create(const char *name,
@@ -510,6 +547,10 @@ static int lxc_one_cgroup_create(const char *name,
SYSERROR("Failed creating pathname for cgroup parent (%d)\n",
ret);
return -1;
}
+
+ if (enable_hierarchy(cgparent))
+ return -1;
+
ret = snprintf(cgname, MAXPATHLEN, "%s/%s", cgparent, name);
if (ret < 0 || ret >= MAXPATHLEN) {
SYSERROR("Failed creating pathname for cgroup (%d)\n", ret);
--
1.8.0
-serge
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