From: Johannes Weiner <hannes@cmpxchg.org>
To: Barry Song <baohua@kernel.org>
Cc: Xueyuan Chen <xueyuan.chen21@gmail.com>,
akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
zhaonanzhe@xiaomi.com, mhocko@kernel.org,
roman.gushchin@linux.dev, shakeel.butt@linux.dev,
muchun.song@linux.dev, chrisl@kernel.org, kasong@tencent.com,
shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com,
youngjun.park@lge.com, david@kernel.org, ljs@kernel.org,
liam@infradead.org, vbabka@kernel.org, rppt@kernel.org,
surenb@google.com, qi.zheng@linux.dev, axelrasmussen@google.com,
yuanchu@google.com, weixugc@google.com,
baolin.wang@linux.alibaba.com, hughd@google.com
Subject: Re: [RFC PATCH v3 2/4] mm: distinguish large folio swap allocation failures
Date: Tue, 21 Jul 2026 07:53:33 -0400 [thread overview]
Message-ID: <al9dvQtSwAkKSvQ4@cmpxchg.org> (raw)
In-Reply-To: <CAGsJ_4xv2AGrLY2PBA77fZiqctPEt_ERcUXUvFOdOG72LD_usQ@mail.gmail.com>
On Tue, Jul 21, 2026 at 04:15:13PM +0800, Barry Song wrote:
> On Fri, Jul 17, 2026 at 8:25 PM Xueyuan Chen <xueyuan.chen21@gmail.com> wrote:
> > @@ -5495,6 +5497,9 @@ int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry)
> > rcu_read_lock();
> > memcg = obj_cgroup_memcg(objcg);
> > if (!entry.val) {
> > + if (nr_swap_pages && !mem_cgroup_is_root(memcg))
> > + *nr_swap_pages = min(*nr_swap_pages,
> > + page_counter_margin(&memcg->swap));
>
> This looks a bit odd. Could we decouple *nr_swap_pages from margin and
> have the function always return margin instead?
>
> I don't think this function needs to care about the initial value returned by
> get_nr_swap_pages(). While folio_alloc_swap() may depend on it, they're
> different software layers, and we shouldn't couple them together.
Agreed!
next prev parent reply other threads:[~2026-07-21 11:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-17 12:25 [RFC PATCH v3 0/4] mm: avoid large folio splits when swap is unavailable Xueyuan Chen
2026-07-17 12:25 ` [RFC PATCH v3 1/4] mm: add page_counter_margin() Xueyuan Chen
2026-07-17 12:25 ` [RFC PATCH v3 2/4] mm: distinguish large folio swap allocation failures Xueyuan Chen
2026-07-21 8:15 ` Barry Song
2026-07-21 11:53 ` Johannes Weiner [this message]
2026-07-23 14:49 ` Xueyuan Chen
2026-07-21 16:13 ` Youngjun Park
2026-07-23 15:15 ` Xueyuan Chen
2026-07-17 12:25 ` [RFC PATCH v3 3/4] mm/vmscan: avoid pointless large folio splits without swap Xueyuan Chen
2026-07-21 8:00 ` Barry Song
2026-07-17 12:25 ` [RFC PATCH v3 4/4] mm/shmem: split large folios only on -E2BIG Xueyuan Chen
2026-07-21 7:57 ` Barry Song
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