Re: [PATCH] powerpc/mm: Implemented default_hugepagesz verification for powerpc

From: victora
Date: Wed Jul 12 2017 - 11:14:48 EST

Em 2017-07-05 13:03, victora escreveu:
Em 2017-07-05 01:26, Aneesh Kumar K.V escreveu:
On Tuesday 04 July 2017 01:35 AM, Victor Aoqui wrote:
Implemented default hugepage size verification (default_hugepagesz=)
in order to allow allocation of defined number of pages (hugepages=)
only for supported hugepage sizes.

Signed-off-by: Victor Aoqui <victora@xxxxxxxxxx>
arch/powerpc/mm/hugetlbpage.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index a4f33de..464e72e 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -797,6 +797,21 @@ static int __init hugepage_setup_sz(char *str)
__setup("hugepagesz=", hugepage_setup_sz);

+static int __init default_hugepage_setup_sz(char *str)
+ unsigned long long size;
+ size = memparse(str, &str);
+ if (add_huge_page_size(size) != 0) {
+ hugetlb_bad_size();
+ pr_err("Invalid default huge page size specified(%llu)\n", size);
+ }
+ return 1;
+__setup("default_hugepagesz=", default_hugepage_setup_sz);

isn't that a behavior change in what we have now ? . Right now if size
specified is not supported, we fallback to HPAGE_SIZE.

Yes, it is. However, is this a correct behavior? If we specify an
unsupported value, for example default_hugepagesz=1M and
hugepages=1000, 1M will be ignored and 1000 pages of 16M (arch
default) will be allocated. This could lead to non-expected out of of
memory/performance issue.


if (!size_to_hstate(default_hstate_size)) {
default_hstate_size = HPAGE_SIZE;
if (!size_to_hstate(default_hstate_size))

struct kmem_cache *hugepte_cache;
static int __init hugetlbpage_init(void)

Even if we want to do this, this should be done in generic code and
should not be powerpc specific

The verification of supported powerpc hugepage size (hugepagesz=) is
being performed on add_huge_page_size(), which is currently defined in
arch/powerpc/mm/hugetlbpage.c. I think it makes more sense to
implement default_hugepagesz= verification on arch/powerpc, don't you


Hi Aneesh,

Did you have time to review the comments above?