Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.32 as permitted sender) client-ip=23.128.96.32;
MIME-Version: 1.0
References: <20231113130601.3350915-1-hezhongkun.hzk@bytedance.com>
 <CAJD7tkY8SwROmNEaBAhkS4OKj33g-6fHsKFeYKW3afT+yAbvxA@mail.gmail.com>
 <CAF8kJuPonfuOtipdifXwBny2H7cy6m6BL8mWFVXzfb9JSdYq3Q@mail.gmail.com>
 <CAJD7tkYMiJiXTTgAN34TP8QTr-ViAuEFddYes=ac+1ErenjCZw@mail.gmail.com>
 <CAF8kJuOC30feLGs0bNHOxMjSZ3uqF1y7eUdJ4p-w-myP8c1cFg@mail.gmail.com>
 <8734x1cdtr.fsf@yhuang6-desk2.ccr.corp.intel.com> <CAF8kJuPs=O7dKQYWAyM5N1UPyCkEmaCb9REHmNvAi7o4tPbMDg@mail.gmail.com>
 <87v89xasq0.fsf@yhuang6-desk2.ccr.corp.intel.com>
In-Reply-To: <87v89xasq0.fsf@yhuang6-desk2.ccr.corp.intel.com>
From:   Chris Li <chrisl@kernel.org>
Date:   Sun, 19 Nov 2023 21:51:59 -0800
Message-ID: <CAF8kJuMB8VOvUUssgULnBZnnA00tdW9itXKqwvxReynV1Q6K_Q@mail.gmail.com>
Subject: Re: [PATCH] mm:zswap: fix zswap entry reclamation failure in two scenarios
To:     "Huang, Ying" <ying.huang@intel.com>
Cc:     Yosry Ahmed <yosryahmed@google.com>,
        Zhongkun He <hezhongkun.hzk@bytedance.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Nhat Pham <nphamcs@gmail.com>,
        Seth Jennings <sjenning@redhat.com>,
        Dan Streetman <ddstreet@ieee.org>,
        Vitaly Wool <vitaly.wool@konsulko.com>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Sun, Nov 19, 2023 at 9:41=E2=80=AFPM Huang, Ying <ying.huang@intel.com> =
wrote:
>
> Chris Li <chrisl@kernel.org> writes:
>
> > On Sun, Nov 19, 2023 at 7:20=E2=80=AFPM Huang, Ying <ying.huang@intel.c=
om> wrote:
>
> Per my understanding, memcg uncharging happens in
>
> swapcache_free_entries()
>   swap_entry_free()
>     mem_cgroup_uncharge_swap()
>
> The swap entries are uncharged one-by-one, not

Yes. That matches my understanding as well.
I think I am using the term "batching" very loosely. My bad and thanks
for the clarification.

I am referring to the fact that in most cases, the free_swap_slot()
does not perform uncharge.
It is grouped together with other entries to uncharge together inside
swapcache_free_entries(). Yes, the uncharge itself is done by a for
loop page by page. No batching in the for loop. BTW, Not all uncharges
can be batched, because they can come from different memcg.

Chris