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Wed, 04 Mar 2026 08:50:08 -0800 (PST) MIME-Version: 1.0 References: <20260304151120.3512645-1-joshua.hahnjy@gmail.com> In-Reply-To: From: Nhat Pham Date: Wed, 4 Mar 2026 08:49:57 -0800 X-Gm-Features: AaiRm51ko9kVS8IjAoCAT_NvsIsy1-qAXevpqNGzCEvGG_N_B6mgqJbBAi3r5s8 Message-ID: Subject: Re: [PATCH 6/8] mm/zsmalloc, zswap: Handle objcg charging and lifetime in zsmalloc To: Yosry Ahmed Cc: Joshua Hahn , Minchan Kim , Sergey Senozhatsky , Johannes Weiner , Yosry Ahmed , Nhat Pham , Chengming Zhou , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A18E1120005 X-Stat-Signature: cqi3izoo3a7npk3xr9a5rx7muk8qep1d X-Rspam-User: X-HE-Tag: 1772643010-213202 X-HE-Meta: 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 Jnx+gLoI 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 4, 2026 at 8:46=E2=80=AFAM Yosry Ahmed wrote= : > > > > AFAICT the only zswap-specific part is the actual stat indexes, what > > > if these are parameterized at the zsmalloc pool level? AFAICT zswap > > > and zram will never share a pool. > > > > TBH, if we were to start from scratch, these should be zsmalloc > > counters not zswap counters. Only zsmalloc knows about the memory > > placement and real memory consumption (i.e taking into account > > intra-slot wasted space) - this information is abstracted away from > > all of the callers. > > I agree, but we cannot change the zswap stats now that we added them. > Keep in mind that when they were added zsmalloc was not the only > backend. > > > And if/when zram supports cgroup tracking, memory > > used by zswap and memory used by zram is indistinguishable, no? > > It is distinguishable as long as they use different zsmalloc pools, I > don't see why we'd need to share a pool. > > > Anyway, Joshua, do you think this is doable? Seems promising to me, > > but idk if it will be clean to implement or not. > > Not sure what you mean here? Changing the stats to be zsmalloc-based? > IIUC we can't do this without breaking userspace. No I meant your proposal haha. Sorry for being confusing - probably need more caffeine :)