On 7/19/20 11:26 PM, Baoquan He wrote:
> A customer complained that no any message is printed out when failed to
> allocate explicitly specified number of persistent huge pages. That
> specifying can be done by writing into /proc/sys/vm/nr_hugepages to
> increase the persisten huge pages.
>
> In the current code, it takes the best effort way to allocate the expected
> number of huge pages. If only succeeding to get part of them, no any
> information is printed out.
>
> Here try to send out warning message if the expected number of huge pages
> adjustment is not achieved, including increasing and decreasing the count
> of persistent huge pages.
Perhaps change the wording a bit,
A customer complained that no message is logged when the number of
persistent huge pages is not changed to the exact value written to
the sysfs or proc nr_hugepages file.
In the current code, a best effort is made to satisfy requests made
via the nr_hugepages file. However, requests may be only partially
satisfied.
Log a message if the code was unsuccessful in fully satisfying a
request. This includes both increasing and decreasing the number
of persistent huge pages.
>
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
> ---
> mm/hugetlb.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
I am not opposed to this patch. However, I believe the best way for a user
to determine if their request was successful is to compare the value of
nr_hugepages to the value which was written.
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 467894d8332a..1dfb5d9e4e06 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2661,7 +2661,7 @@ static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
> static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
> nodemask_t *nodes_allowed)
> {
> - unsigned long min_count, ret;
> + unsigned long min_count, ret, old_max;
> NODEMASK_ALLOC(nodemask_t, node_alloc_noretry, GFP_KERNEL);
>
> /*
> @@ -2723,6 +2723,7 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
> * pool might be one hugepage larger than it needs to be, but
> * within all the constraints specified by the sysctls.
> */
> + old_max = persistent_huge_pages(h);
> while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {
> if (!adjust_pool_surplus(h, nodes_allowed, -1))
> break;
> @@ -2779,6 +2780,16 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
> }
> out:
> h->max_huge_pages = persistent_huge_pages(h);
> + if (count != h->max_huge_pages) {
> + char buf[32];
> +
> + string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
> + pr_warn("HugeTLB: %s %lu of page size %s failed. Only %s %lu hugepages.\n",
> + count > old_max ? "increasing" : "decreasing",
> + abs(count - old_max), buf,
> + count > old_max ? "increased" : "decreased",
> + abs(old_max - h->max_huge_pages));
> + }
> spin_unlock(&hugetlb_lock);
I would prefer if we drop the lock before logging the message. That would
involve grabbing the value of h->max_huge_pages before dropping the lock.
--
Mike Kravetz
>
> NODEMASK_FREE(node_alloc_noretry);
>
