mm/hugetlb_cgroup: introduce peak and rsvd.peak to v2

Introduce peak and rsvd.peak to v2 to show the historical maximum usage of
resources, as in some scenarios it is necessary to configure the value of
max/rsvd.max based on the peak usage of resources.

Since HugeTLB doesn't support page reclaim, enforcing the limit at page
fault time implies that, the application will get SIGBUS signal if it
tries to fault in HugeTLB pages beyond its limit.  Therefore the
application needs to know exactly how many HugeTLB pages it uses before
hand, and the sysadmin needs to make sure that there are enough available
on the machine for all the users to avoid processes getting SIGBUS.

When running some open-source software, it may not be possible to know the
exact amount of hugetlb it consumes, so cannot correctly configure the max
value.  If there is a peak metric, we can run the open-source software
first and then configure the max based on the peak value.  In cgroup v1,
the hugetlb controller provides the max_usage_in_bytes and
rsvd.max_usage_in_bytes interface to display the historical maximum usage,
so introduce peak and rsvd.peak to v2 to address this issue.

Link: https://lkml.kernel.org/r/20240702125728.2743143-1-xiujianfeng@huawei.com
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index bd7e81c2aa2b8700c44f5f834277c604648a8c55..db3799f1483e5492049a4be6bb10feae7885932a 100644 (file)
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -2650,6 +2650,14 @@ HugeTLB Interface Files
         hugetlb pages of <hugepagesize> in this cgroup.  Only active in
         use hugetlb pages are included.  The per-node values are in bytes.
 
+  hugetlb.<hugepagesize>.peak
+       Show historical maximum usage for "hugepagesize" hugetlb.  It exists
+        for all the cgroup except root.
+
+  hugetlb.<hugepagesize>.rsvd.peak
+       Show historical maximum usage for "hugepagesize" hugetlb reservations.
+        It exists for all the cgroup except root.
+
 Misc
 ----
 

diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index e716c4671a1595366e876d51fd34faf3f91fa81d..d8d0e665caed90294b4db69d7b8d074770d6be12 100644 (file)
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -583,6 +583,13 @@ static int hugetlb_cgroup_read_u64_max(struct seq_file *seq, void *v)
                else
                        seq_printf(seq, "%llu\n", val * PAGE_SIZE);
                break;
+       case RES_RSVD_MAX_USAGE:
+               counter = &h_cg->rsvd_hugepage[idx];
+               fallthrough;
+       case RES_MAX_USAGE:
+               val = (u64)counter->watermark;
+               seq_printf(seq, "%llu\n", val * PAGE_SIZE);
+               break;
        default:
                BUG();
        }
@@ -739,6 +746,18 @@ static struct cftype hugetlb_dfl_tmpl[] = {
                .seq_show = hugetlb_cgroup_read_u64_max,
                .flags = CFTYPE_NOT_ON_ROOT,
        },
+       {
+               .name = "peak",
+               .private = RES_MAX_USAGE,
+               .seq_show = hugetlb_cgroup_read_u64_max,
+               .flags = CFTYPE_NOT_ON_ROOT,
+       },
+       {
+               .name = "rsvd.peak",
+               .private = RES_RSVD_MAX_USAGE,
+               .seq_show = hugetlb_cgroup_read_u64_max,
+               .flags = CFTYPE_NOT_ON_ROOT,
+       },
        {
                .name = "events",
                .seq_show = hugetlb_events_show,