From: Paul Jackson <[email protected]>
Fix memory migration so that it works regardless of what cpuset
the invoking task is in.
If a task invoked a memory migration, by doing one of:
1) writing a different nodemask to a cpuset 'mems' file, or
2) writing a tasks pid to a different cpuset's 'tasks' file,
where the cpuset had its 'memory_migrate' option turned on,
then the allocation of the new pages for the migrated task(s)
was constrained by the invoking tasks cpuset.
If this task wasn't in a cpuset that allowed the requested
memory nodes, the memory migration would happen to some other
nodes that were in that invoking tasks cpuset. This was usually
surprising and puzzling behaviour: Why didn't the pages move?
Why did the pages move -there-?
To fix this, temporarilly change the invoking tasks
'mems_allowed' task_struct field to the nodes the migrating
tasks is moving to, so that new pages can be allocated there.
Signed-off-by: Paul Jackson <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
---
Finally a fix for this interaction of cpusets with memory migration.
I am hoping that this will be suitable for 2.6.17, as memory migration
fails in unexpected ways without this fix. -pj
kernel/cpuset.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 52 insertions(+), 5 deletions(-)
--- 2.6.16-mm1.orig/kernel/cpuset.c 2006-03-27 08:44:47.894113580 -0800
+++ 2.6.16-mm1/kernel/cpuset.c 2006-03-27 08:47:46.400307814 -0800
@@ -834,6 +834,55 @@ static int update_cpumask(struct cpuset
}
/*
+ * cpuset_migrate_mm
+ *
+ * Migrate memory region from one set of nodes to another.
+ *
+ * Temporarilly set tasks mems_allowed to target nodes of migration,
+ * so that the migration code can allocate pages on these nodes.
+ *
+ * Call holding manage_mutex, so our current->cpuset won't change
+ * during this call, as manage_mutex holds off any attach_task()
+ * calls. Therefore we don't need to take task_lock around the
+ * call to guarantee_online_mems(), as we know no one is changing
+ * our tasks cpuset.
+ *
+ * Hold callback_mutex around the two modifications of our tasks
+ * mems_allowed to synchronize with cpuset_mems_allowed().
+ *
+ * While the mm_struct we are migrating is typically from some
+ * other task, the task_struct mems_allowed that we are hacking
+ * is for our current task, which must allocate new pages for that
+ * migrating memory region.
+ *
+ * We call cpuset_update_task_memory_state() before hacking
+ * our tasks mems_allowed, so that we are assured of being in
+ * sync with our tasks cpuset, and in particular, callbacks to
+ * cpuset_update_task_memory_state() from nested page allocations
+ * won't see any mismatch of our cpuset and task mems_generation
+ * values, so won't overwrite our hacked tasks mems_allowed
+ * nodemask.
+ */
+
+static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
+ const nodemask_t *to)
+{
+ struct task_struct *tsk = current;
+
+ cpuset_update_task_memory_state();
+
+ mutex_lock(&callback_mutex);
+ tsk->mems_allowed = *to;
+ mutex_unlock(&callback_mutex);
+
+ do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);
+
+ mutex_lock(&callback_mutex);
+ guarantee_online_mems(tsk->cpuset, &tsk->mems_allowed);
+ mutex_unlock(&callback_mutex);
+}
+
+/*
* Handle user request to change the 'mems' memory placement
* of a cpuset. Needs to validate the request, update the
* cpusets mems_allowed and mems_generation, and for each
@@ -945,10 +994,8 @@ static int update_nodemask(struct cpuset
struct mm_struct *mm = mmarray[i];
mpol_rebind_mm(mm, &cs->mems_allowed);
- if (migrate) {
- do_migrate_pages(mm, &oldmem, &cs->mems_allowed,
- MPOL_MF_MOVE_ALL);
- }
+ if (migrate)
+ cpuset_migrate_mm(mm, &oldmem, &cs->mems_allowed);
mmput(mm);
}
@@ -1184,7 +1231,7 @@ static int attach_task(struct cpuset *cs
if (mm) {
mpol_rebind_mm(mm, &to);
if (is_memory_migrate(cs))
- do_migrate_pages(mm, &from, &to, MPOL_MF_MOVE_ALL);
+ cpuset_migrate_mm(mm, &from, &to);
mmput(mm);
}
--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <[email protected]> 1.650.933.1373
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