From 8a63011275e1a0ec9389e8c7d9b08caab8957ca0 Mon Sep 17 00:00:00 2001 From: Ken Chen Date: Wed, 9 May 2007 02:33:34 -0700 Subject: [PATCH] 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 Cc: Paul Jackson Cc: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/hugetlb.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 88e708be1f..eb7180db30 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; -- 2.39.5