Re: [PATCH v7] hugetlb: Add hugetlb.*.numa_stat file
From: Mike Kravetz <hidden>
Date: 2021-11-18 00:13:19
Also in:
cgroups, linux-mm, lkml
On 11/17/21 12:18, Mina Almasry wrote: ...
quoted hunk ↗ jump to hunk
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
...
quoted hunk ↗ jump to hunk
@@ -288,11 +317,21 @@ static void __hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages, struct hugetlb_cgroup *h_cg, struct page *page, bool rsvd) { + unsigned long *usage; +
I assume the use of a pointer is just to make the following WRITE_ONCE look better? I prefer the suggestion by Muchun: unsigned long usage = h_cg->nodeinfo[page_to_nid(page)]->usage[idx]; usage += nr_pages; WRITE_ONCE(h_cg->nodeinfo[page_to_nid(page)]->usage[idx], usage); I had to think for just a second 'why are we using/passing a pointer?'. Not insisting we use Muchun's suggestion, it just caused me to think a little more than necessary. In any case, I would move the variable usage inside the 'if (!rsvd)' block.
quoted hunk ↗ jump to hunk
if (hugetlb_cgroup_disabled() || !h_cg) return; __set_hugetlb_cgroup(page, h_cg, rsvd); - return; + if (!rsvd) { + usage = &h_cg->nodeinfo[page_to_nid(page)]->usage[idx]; + /* + * This write is not atomic due to fetching *usage and writing + * to it, but that's fine because we call this with + * hugetlb_lock held anyway. + */ + WRITE_ONCE(*usage, *usage + nr_pages); + } } void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,@@ -316,6 +355,7 @@ static void __hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages, struct page *page, bool rsvd) { struct hugetlb_cgroup *h_cg; + unsigned long *usage;
Same here. Otherwise, looks good to me. -- Mike Kravetz