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.
- Check for hugepages_supported() before processing parameters.
- Add comments to code
- Describe some of the subtle interactions
- Describe semantics of command line arguments
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 35 ++++---
Documentation/admin-guide/mm/hugetlbpage.rst | 44 +++++++++
mm/hugetlb.c | 96 +++++++++++++++----
3 files changed, 142 insertions(+), 33 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1bd5454b5e5f..de653cfe1726 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -832,12 +832,15 @@
See also Documentation/networking/decnet.txt.
default_hugepagesz=
- [same as hugepagesz=] The size of the default
- HugeTLB page size. This is the size represented by
- the legacy /proc/ hugepages APIs, used for SHM, and
- default size when mounting hugetlbfs filesystems.
- Defaults to the default architecture's huge page size
- if not specified.
+ [HW] The size of the default HugeTLB page size. This
+ is the size represented by the legacy /proc/ hugepages
+ APIs. In addition, this is the default hugetlb size
+ used for shmget(), mmap() and mounting hugetlbfs
+ filesystems. If not specified, defaults to the
+ architecture's default huge page size. Huge page
+ sizes are architecture dependent. See also
+ Documentation/admin-guide/mm/hugetlbpage.rst.
+ Format: size[KMG]
deferred_probe_timeout=
[KNL] Debugging option to set a timeout in seconds for
@@ -1480,13 +1483,19 @@
If enabled, boot-time allocation of gigantic hugepages
is skipped.
- hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
- hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
- On x86-64 and powerpc, this option can be specified
- multiple times interleaved with hugepages= to reserve
- huge pages of different sizes. Valid pages sizes on
- x86-64 are 2M (when the CPU supports "pse") and 1G
- (when the CPU supports the "pdpe1gb" cpuinfo flag).
+ hugepages= [HW] Number of HugeTLB pages to allocate at boot.
+ If this follows hugepagesz (below), it specifies
+ the number of pages of hugepagesz to be allocated.
+ Format: <integer>
+ hugepagesz=
+ [HW] The size of the HugeTLB pages. This is used in
+ conjunction with hugepages (above) to allocate huge
+ pages of a specific size at boot. The pair
+ hugepagesz=X hugepages=Y can be specified once for
+ each supported huge page size. Huge page sizes are
+ architecture dependent. See also
+ Documentation/admin-guide/mm/hugetlbpage.rst.
+ Format: size[KMG]
hung_task_panic=
[KNL] Should the hung task detector generate panics.
diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
index 1cc0bc78d10e..de340c586995 100644
--- a/Documentation/admin-guide/mm/hugetlbpage.rst
+++ b/Documentation/admin-guide/mm/hugetlbpage.rst
@@ -100,6 +100,50 @@ 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 once on the command line. No other hugetlb command
+ line parameter is associated with default_hugepagesz. Therefore, it
+ can appear anywhere on the command line. If hugepages= is the first
+ hugetlb command line parameter, the specified number of huge pages
+ will apply to the default huge page size specified with
+ default_hugepagesz. For example,
+ hugepages=512 default_hugepagesz=2M
+ will result in 512 2M huge pages being allocated. However, specifying
+ the number of default huge pages in this manner will not apply to
+ gigantic huge pages. For example,
+ hugepages=10 default_hugepagesz=1G
+ or
+ default_hugepagesz=1G hugepages=10
+ will NOT result in the allocation of 10 1G huge pages. In order to
+ preallocate gigantic huge pages, there must be hugepagesz, hugepages
+ parameter pair. For example,
+ hugepagesz=1G hugepages=10 default_hugepagesz=1G
+ or
+ default_hugepagesz=1G hugepagesz=1G hugepages=10
+ will result 10 1G huge pages being allocated and the default huge
+ page size will be set to 1G. 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 72a4343509d5..74ef53f7c5a7 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3054,7 +3054,7 @@ 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);
}
}
@@ -3158,7 +3158,7 @@ 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;
@@ -3209,19 +3209,35 @@ 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 ignored\n",
+ default_hstate_max_huge_pages);
}
hugetlb_init_hstates();
@@ -3274,20 +3290,31 @@ void __init hugetlb_add_hstate(unsigned int order)
parsed_hstate = h;
}
-static int __init hugetlb_nrpages_setup(char *s)
+/*
+ * hugepages command line processing
+ * hugepages 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 (!hugepages_supported()) {
+ pr_warn("HugeTLB: huge pages not supported, ignoring hugepages = %s\n", s);
+ return 0;
+ }
+
if (!parsed_valid_hugepagesz) {
- pr_warn("hugepages = %s preceded by "
- "an unsupported hugepagesz, ignoring\n", s);
+ pr_warn("HugeTLB: hugepages = %s preceded by an unsupported hugepagesz, ignoring\n", s);
parsed_valid_hugepagesz = true;
- return 1;
+ return 0;
}
/*
- * !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;
@@ -3295,8 +3322,8 @@ 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");
- return 1;
+ pr_warn("HugeTLB: hugepages= specified twice without interleaving hugepagesz=, ignoring hugepages=%s\n", s);
+ return 0;
}
if (sscanf(s, "%lu", mhp) <= 0)
@@ -3314,12 +3341,24 @@ 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 command 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 size;
+ if (!hugepages_supported()) {
+ pr_warn("HugeTLB: huge pages not supported, ignoring hugepagesz = %s\n", s);
+ return 0;
+ }
+
size = (unsigned long)memparse(s, NULL);
if (!arch_hugetlb_valid_size(size)) {
@@ -3329,19 +3368,31 @@ 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", 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 size;
+ if (!hugepages_supported()) {
+ pr_warn("HugeTLB: huge pages not supported, ignoring default_hugepagesz = %s\n", s);
+ return 0;
+ }
+
size = (unsigned long)memparse(s, NULL);
if (!arch_hugetlb_valid_size(size)) {
@@ -3349,6 +3400,11 @@ static int __init default_hugepagesz_setup(char *s)
return 0;
}
+ if (default_hstate_size) {
+ pr_err("HugeTLB: default_hugepagesz previously specified, ignoring %s\n", s);
+ return 0;
+ }
+
default_hstate_size = size;
return 1;
}
--
2.25.1
