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authorKen Chen <kenchen@google.com>2007-05-09 02:33:34 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-09 12:30:49 -0700
commit8a63011275e1a0ec9389e8c7d9b08caab8957ca0 (patch)
treeae631cb1206c60a8b375384a880cabf7dc156d00 /mm/hugetlb.c
parent85badbdf5120d246ce2bb3f1a7689a805f9c9006 (diff)
pretend cpuset has some form of hugetlb page reservation
When cpuset is configured, it breaks the strict hugetlb page reservation as the accounting is done on a global variable. Such reservation is completely rubbish in the presence of cpuset because the reservation is not checked against page availability for the current cpuset. Application can still potentially OOM'ed by kernel with lack of free htlb page in cpuset that the task is in. Attempt to enforce strict accounting with cpuset is almost impossible (or too ugly) because cpuset is too fluid that task or memory node can be dynamically moved between cpusets. The change of semantics for shared hugetlb mapping with cpuset is undesirable. However, in order to preserve some of the semantics, we fall back to check against current free page availability as a best attempt and hopefully to minimize the impact of changing semantics that cpuset has on hugetlb. Signed-off-by: Ken Chen <kenchen@google.com> Cc: Paul Jackson <pj@sgi.com> Cc: Christoph Lameter <clameter@engr.sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r--mm/hugetlb.c31
1 files changed, 31 insertions, 0 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 88e708be1f6..eb7180db303 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -174,6 +174,17 @@ static int __init hugetlb_setup(char *s)
}
__setup("hugepages=", hugetlb_setup);
+static unsigned int cpuset_mems_nr(unsigned int *array)
+{
+ int node;
+ unsigned int nr = 0;
+
+ for_each_node_mask(node, cpuset_current_mems_allowed)
+ nr += array[node];
+
+ return nr;
+}
+
#ifdef CONFIG_SYSCTL
static void update_and_free_page(struct page *page)
{
@@ -819,6 +830,26 @@ int hugetlb_reserve_pages(struct inode *inode, long from, long to)
chg = region_chg(&inode->i_mapping->private_list, from, to);
if (chg < 0)
return chg;
+ /*
+ * When cpuset is configured, it breaks the strict hugetlb page
+ * reservation as the accounting is done on a global variable. Such
+ * reservation is completely rubbish in the presence of cpuset because
+ * the reservation is not checked against page availability for the
+ * current cpuset. Application can still potentially OOM'ed by kernel
+ * with lack of free htlb page in cpuset that the task is in.
+ * Attempt to enforce strict accounting with cpuset is almost
+ * impossible (or too ugly) because cpuset is too fluid that
+ * task or memory node can be dynamically moved between cpusets.
+ *
+ * The change of semantics for shared hugetlb mapping with cpuset is
+ * undesirable. However, in order to preserve some of the semantics,
+ * we fall back to check against current free page availability as
+ * a best attempt and hopefully to minimize the impact of changing
+ * semantics that cpuset has.
+ */
+ if (chg > cpuset_mems_nr(free_huge_pages_node))
+ return -ENOMEM;
+
ret = hugetlb_acct_memory(chg);
if (ret < 0)
return ret;