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Message-ID: <86d3ba7a-3706-d66c-cbf7-d2c39ad2cd4c@oracle.com>
Date: Wed, 17 Nov 2021 16:12:49 -0800
From: Mike Kravetz <mike.kravetz@...cle.com>
To: Mina Almasry <almasrymina@...gle.com>, Tejun Heo <tj@...nel.org>,
Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>,
Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Shuah Khan <shuah@...nel.org>, Miaohe Lin <linmiaohe@...wei.com>,
Oscar Salvador <osalvador@...e.de>,
Michal Hocko <mhocko@...e.com>,
Muchun Song <songmuchun@...edance.com>,
David Rientjes <rientjes@...gle.com>,
Shakeel Butt <shakeelb@...gle.com>, Jue Wang <juew@...gle.com>,
Yang Yao <ygyao@...gle.com>, Joanna Li <joannali@...gle.com>,
Cannon Matthews <cannonmatthews@...gle.com>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
cgroups@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v7] hugetlb: Add hugetlb.*.numa_stat file
On 11/17/21 12:18, Mina Almasry wrote:
...
> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
...
> @@ -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.
> 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
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