On Thu, Mar 14, 2013 at 10:44:19AM +0100, Michal Hocko wrote:
>On Wed 13-03-13 15:08:31, Wanpeng Li wrote:
>> After commit 42d7395f ("mm: support more pagesizes for MAP_HUGETLB/SHM_HUGETLB")
>> be merged, kernel permit multiple huge page sizes,
>
Hi Michal,
>multiple huge page sizes were possible long before this commit. The
>above mentioned patch just made their usage via IPC much easier. You
>could do the same previously (since a137e1cc) by mounting hugetlbfs with
>a specific page size as a parameter and using mmap.
>
Agreed.
>> and when the system administrator has configured the system to provide
>> huge page pools of different sizes, application can choose the page
>> size used for their allocation.
>
>> However, just default size of huge page pool is statistical when
>> memory overcommit accouting, the bad is that this will result in
>> innocent processes be killed by oom-killer later.
>
>Why would an innnocent process be killed? The overcommit calculation
>is incorrect, that is true, but this just means that an unexpected
>ENOMEM/EFAULT or SIGSEGV would be returned, no? How an OOM could be a
>result?
Agreed.
>
>> Fix it by statistic all huge page pools of different sizes provided by
>> administrator.
>
>The patch makes sense but the description is misleading AFAICS.
>
Thanks for your pointing out Michal, I will update the description. :-)
Regards,
Wanpeng Li
>> Testcase:
>> boot: hugepagesz=1G hugepages=1
>> before patch:
>> egrep 'CommitLimit' /proc/meminfo
>> CommitLimit: 55434168 kB
>> after patch:
>> egrep 'CommitLimit' /proc/meminfo
>> CommitLimit: 54909880 kB
>>
>> Signed-off-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
>> ---
>> mm/hugetlb.c | 7 +++++--
>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index cdb64e4..9e25040 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -2124,8 +2124,11 @@ int hugetlb_report_node_meminfo(int nid, char *buf)
>> /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
>> unsigned long hugetlb_total_pages(void)
>> {
>> - struct hstate *h = &default_hstate;
>> - return h->nr_huge_pages * pages_per_huge_page(h);
>> + struct hstate *h;
>> + unsigned long nr_total_pages = 0;
>> + for_each_hstate(h)
>> + nr_total_pages += h->nr_huge_pages * pages_per_huge_page(h);
>> + return nr_total_pages;
>> }
>>
>> static int hugetlb_acct_memory(struct hstate *h, long delta)
>> --
>> 1.7.11.7
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@xxxxxxxxx. For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
>
>--
>Michal Hocko
>SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>