(1) Background
For the arm64, the hugetlb page size can be 32M (PMD + Contiguous bit).
In the 4K page environment, the max page order is 10 (max_order - 1),
so 32M page is the gigantic page.
The arm64 MMU supports a Contiguous bit which is a hint that the TTE
is one of a set of contiguous entries which can be cached in a single
TLB entry. Please refer to the arm64v8 mannul :
DDI0487A_f_armv8_arm.pdf (in page D4-1811)
(2) The bug
After I tested the libhugetlbfs, I found the test case "counter.sh"
will fail with the gigantic page (32M page in arm64 board).
The counter.sh is just a wrapper for counter.c.
You can find them in:
https://github.com/libhugetlbfs/libhugetlbfs/blob/master/tests/counters.c
https://github.com/libhugetlbfs/libhugetlbfs/blob/master/tests/counters.sh
The error log shows below:
----------------------------------------------------------
...........................................
LD_PRELOAD=libhugetlbfs.so shmoverride_unlinked (32M: 64): PASS
LD_PRELOAD=libhugetlbfs.so HUGETLB_SHM=yes shmoverride_unlinked (32M: 64): PASS
quota.sh (32M: 64): PASS
counters.sh (32M: 64): FAIL mmap failed: Invalid argument
********** TEST SUMMARY
* 32M
* 32-bit 64-bit
* Total testcases: 0 87
* Skipped: 0 0
* PASS: 0 86
* FAIL: 0 1
* Killed by signal: 0 0
* Bad configuration: 0 0
* Expected FAIL: 0 0
* Unexpected PASS: 0 0
* Strange test result: 0 0
**********
----------------------------------------------------------
The failure is caused by:
1) kernel fails to allocate a gigantic page for the surplus case.
And the gather_surplus_pages() will return NULL in the end.
2) The condition checks for some functions are wrong:
return_unused_surplus_pages()
nr_overcommit_hugepages_store()
hugetlb_overcommit_handler()
This patch set adds support for gigantic surplus hugetlb pages,
allowing the counter.sh unit test to pass.
Test this patch set with Juno-r1 board.
v2 -- > v3:
1.) In patch 2, change argument "no_init" to "do_prep"
2.) In patch 3, also change alloc_fresh_huge_page().
In the v2, this patch only changes the alloc_fresh_gigantic_page().
3.) Merge old patch #4,#5 into the last one.
4.) Follow Babka's suggestion, do the NULL check for @mask.
5.) others.
v1 -- > v2:
1.) fix the compiler error in X86.
2.) add new patches for NUMA.
The patch #2 ~ #5 are new patches.
Huang Shijie (4):
mm: hugetlb: rename some allocation functions
mm: hugetlb: add a new parameter for some functions
mm: hugetlb: change the return type for some functions
mm: hugetlb: support gigantic surplus pages
include/linux/mempolicy.h | 8 +++
mm/hugetlb.c | 146 +++++++++++++++++++++++++++++++++++-----------
mm/mempolicy.c | 44 ++++++++++++++
3 files changed, 163 insertions(+), 35 deletions(-)
--
2.5.5
--
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>