[PATCH 4/4] hugetlbfs: clean up command line processing
From: Mike Kravetz
Date: Wed Mar 18 2020 - 18:09:03 EST
With all hugetlb page processing done in a single file clean up code.
- Make code match desired semantics
- Update documentation with semantics
- Make all warnings and errors messages start with 'HugeTLB:'.
- Consistently name command line parsing routines.
- Add comments to code
- Describe some of the subtle interactions
- Describe semantics of command line arguments
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
Documentation/admin-guide/mm/hugetlbpage.rst | 26 +++++++
mm/hugetlb.c | 78 +++++++++++++++-----
2 files changed, 87 insertions(+), 17 deletions(-)
diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
index 1cc0bc78d10e..afc8888f33c3 100644
--- a/Documentation/admin-guide/mm/hugetlbpage.rst
+++ b/Documentation/admin-guide/mm/hugetlbpage.rst
@@ -100,6 +100,32 @@ with a huge page size selection parameter "hugepagesz=<size>". <size> must
be specified in bytes with optional scale suffix [kKmMgG]. The default huge
page size may be selected with the "default_hugepagesz=<size>" boot parameter.
+Hugetlb boot command line parameter semantics
+hugepagesz - Specify a huge page size. Used in conjunction with hugepages
+ parameter to preallocate a number of huge pages of the specified
+ size. Hence, hugepagesz and hugepages are typically specified in
+ pairs such as:
+ hugepagesz=2M hugepages=512
+ hugepagesz can only be specified once on the command line for a
+ specific huge page size. Valid huge page sizes are architecture
+ dependent.
+hugepages - Specify the number of huge pages to preallocate. This typically
+ follows a valid hugepagesz parameter. However, if hugepages is the
+ first or only hugetlb command line parameter it specifies the number
+ of huge pages of default size to allocate. The number of huge pages
+ of default size specified in this manner can be overwritten by a
+ hugepagesz,hugepages parameter pair for the default size.
+ For example, on an architecture with 2M default huge page size:
+ hugepages=256 hugepagesz=2M hugepages=512
+ will result in 512 2M huge pages being allocated. If a hugepages
+ parameter is preceded by an invalid hugepagesz parameter, it will
+ be ignored.
+default_hugepagesz - Specify the default huge page size. This parameter can
+ only be specified on the command line. No other hugetlb command line
+ parameter is associated with default_hugepagesz. Therefore, it can
+ appear anywhere on the command line. Valid default huge page size is
+ architecture dependent.
+
When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages``
indicates the current number of pre-allocated huge pages of the default size.
Thus, one can use the following command to dynamically allocate/deallocate
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index cc85b4f156ca..2b9bf01db2b6 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2954,7 +2954,7 @@ static void __init hugetlb_sysfs_init(void)
err = hugetlb_sysfs_add_hstate(h, hugepages_kobj,
hstate_kobjs, &hstate_attr_group);
if (err)
- pr_err("Hugetlb: Unable to add hstate %s", h->name);
+ pr_err("HugeTLB: Unable to add hstate %s", h->name);
}
}
@@ -3058,7 +3058,7 @@ static void hugetlb_register_node(struct node *node)
nhs->hstate_kobjs,
&per_node_hstate_attr_group);
if (err) {
- pr_err("Hugetlb: Unable to add hstate %s for node %d\n",
+ pr_err("HugeTLB: Unable to add hstate %s for node %d\n",
h->name, node->dev.id);
hugetlb_unregister_node(node);
break;
@@ -3109,19 +3109,35 @@ static int __init hugetlb_init(void)
if (!hugepages_supported())
return 0;
- if (!size_to_hstate(default_hstate_size)) {
- if (default_hstate_size != 0) {
- pr_err("HugeTLB: unsupported default_hugepagesz %lu. Reverting to %lu\n",
- default_hstate_size, HPAGE_SIZE);
- }
-
+ /*
+ * Make sure HPAGE_SIZE (HUGETLB_PAGE_ORDER) hstate exists. Some
+ * architectures depend on setup being done here.
+ *
+ * If a valid default huge page size was specified on the command line,
+ * add associated hstate if necessary. If not, set default_hstate_size
+ * to default size. default_hstate_idx is used at runtime to identify
+ * the default huge page size/hstate.
+ */
+ hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
+ if (default_hstate_size)
+ hugetlb_add_hstate(ilog2(default_hstate_size) - PAGE_SHIFT);
+ else
default_hstate_size = HPAGE_SIZE;
- hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
- }
default_hstate_idx = hstate_index(size_to_hstate(default_hstate_size));
+
+ /*
+ * default_hstate_max_huge_pages != 0 indicates a count (hugepages=)
+ * specified before a size (hugepagesz=). Use this count for the
+ * default huge page size, unless a specific value was specified for
+ * this size in a hugepagesz/hugepages pair.
+ */
if (default_hstate_max_huge_pages) {
if (!default_hstate.max_huge_pages)
- default_hstate.max_huge_pages = default_hstate_max_huge_pages;
+ default_hstate.max_huge_pages =
+ default_hstate_max_huge_pages;
+ else
+ pr_warn("HugeTLB: First hugepages=%lu kB ignored\n",
+ default_hstate_max_huge_pages);
}
hugetlb_init_hstates();
@@ -3174,20 +3190,27 @@ void __init hugetlb_add_hstate(unsigned int order)
parsed_hstate = h;
}
-static int __init hugetlb_nrpages_setup(char *s)
+/*
+ * hugepages command line processing
+ * hugepages must normally follows a valid hugepagsz specification. If not,
+ * ignore the hugepages value. hugepages can also be the first huge page
+ * command line option in which case it specifies the number of huge pages
+ * for the default size.
+ */
+static int __init hugepages_setup(char *s)
{
unsigned long *mhp;
static unsigned long *last_mhp;
if (!parsed_valid_hugepagesz) {
- pr_warn("hugepages = %s preceded by "
+ pr_warn("HugeTLB: hugepages = %s preceded by "
"an unsupported hugepagesz, ignoring\n", s);
parsed_valid_hugepagesz = true;
return 1;
}
/*
- * !hugetlb_max_hstate means we haven't parsed a hugepagesz= parameter yet,
- * so this hugepages= parameter goes to the "default hstate".
+ * !hugetlb_max_hstate means we haven't parsed a hugepagesz= parameter
+ * yet, so this hugepages= parameter goes to the "default hstate".
*/
else if (!hugetlb_max_hstate)
mhp = &default_hstate_max_huge_pages;
@@ -3195,7 +3218,8 @@ static int __init hugetlb_nrpages_setup(char *s)
mhp = &parsed_hstate->max_huge_pages;
if (mhp == last_mhp) {
- pr_warn("hugepages= specified twice without interleaving hugepagesz=, ignoring\n");
+ pr_warn("HugeTLB: hugepages= specified twice without interleaving hugepagesz=, ignoring hugepages=%s\n",
+ s);
return 1;
}
@@ -3214,8 +3238,15 @@ static int __init hugetlb_nrpages_setup(char *s)
return 1;
}
-__setup("hugepages=", hugetlb_nrpages_setup);
+__setup("hugepages=", hugepages_setup);
+/*
+ * hugepagesz command line processing
+ * A specific huge page size can only be specified once with hugepagesz.
+ * hugepagesz is followed by hugepages on the commnad line. The global
+ * variable 'parsed_valid_hugepagesz' is used to determine if prior
+ * hugepagesz argument was valid.
+ */
static int __init hugepagesz_setup(char *s)
{
unsigned long long size;
@@ -3230,16 +3261,23 @@ static int __init hugepagesz_setup(char *s)
}
if (size_to_hstate(size)) {
+ parsed_valid_hugepagesz = false;
pr_warn("HugeTLB: hugepagesz %s specified twice, ignoring\n",
saved_s);
return 0;
}
+ parsed_valid_hugepagesz = true;
hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT);
return 1;
}
__setup("hugepagesz=", hugepagesz_setup);
+/*
+ * default_hugepagesz command line input
+ * Only one instance of default_hugepagesz allowed on command line. Do not
+ * add hstate here as that will confuse hugepagesz/hugepages processing.
+ */
static int __init default_hugepagesz_setup(char *s)
{
unsigned long long size;
@@ -3252,6 +3290,12 @@ static int __init default_hugepagesz_setup(char *s)
return 0;
}
+ if (default_hstate_size) {
+ pr_err("HugeTLB: default_hugepagesz previously specified, ignoring %s\n",
+ saved_s);
+ return 0;
+ }
+
default_hstate_size = size;
return 1;
}
--
2.24.1