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Tue, 21 Nov 2023 10:13:30 -0800 (PST) MIME-Version: 1.0 References: <20231115172344.4155593-1-nphamcs@gmail.com> In-Reply-To: From: Nhat Pham Date: Tue, 21 Nov 2023 10:13:19 -0800 Message-ID: Subject: Re: [PATCH v5] zswap: memcontrol: implement zswap writeback disabling To: Chris Li Cc: Yosry Ahmed , Andrew Morton , tj@kernel.org, lizefan.x@bytedance.com, Johannes Weiner , Domenico Cerasuolo , Seth Jennings , Dan Streetman , Vitaly Wool , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Hugh Dickins , corbet@lwn.net, Konrad Rzeszutek Wilk , senozhatsky@chromium.org, rppt@kernel.org, linux-mm , kernel-team@meta.com, LKML , linux-doc@vger.kernel.org, david@ixit.cz Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 68BD840021 X-Stat-Signature: 3gn5rhbeuw9jswdtuhdrjpn3bz6xtwxb X-HE-Tag: 1700590411-239008 X-HE-Meta: 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 R9k0WTBZ KvIGF8TK16Y11BpijZ6rtwrms+gbYB2isfsV1B7f3D3jIErOoYHhtl6swnMUbbSNHiimA1CPuPdHh6WI97SrUntEu25JxDRNh1EpJydXepi8ZydHWf7ATsQVVOEXRHYprc0rz6I4TmPGqqT8bDl9iT1QVrHQnWFebFF1uHrn15KzMjjO0KHJ/dM564XjZO1Omv826hVQmuBVbUEYYnwLeQgHlHCgINw/Yiqw/r3YEi46nNW0i+YRJCddkoah6zY7pLeFpg7pDFNNM/B0s+Su3hq5NQ2RMVY1gtO0sDQLe4NsP+kkWlgak4B9rkXXBhG80wqVPX+8/zMMz4fKlA5EFA3Qc691J8br9mpU6DoJP5uDD4TYSK+po1jJQ8UXX+OFAnUzNFZMSrvDgKXGiPiLdaYfaSwKhzTdYoqP/iJLG+3hkQjqjSp/0JbNN2Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Nov 19, 2023 at 6:41=E2=80=AFPM Chris Li wrote: > > Hi Nhat, > > On Sun, Nov 19, 2023 at 01:50:17PM -0800, Chris Li wrote: > > On Sun, Nov 19, 2023 at 11:08=E2=80=AFAM Nhat Pham = wrote: > > > I don't have any major argument against this. It just seems a bit > > > heavyweight for what we need at the moment (only disabling > > > swap-to-disk usage). > > > > The first milestone we just implement the reserved keywords without > > the custom swap tier list. > > That should be very similar to "zswap.writeback". Instead of writing 0 > > to "zswap.writeback". > > You write "zswap" to "swap.tiers". Writing "none" will disable all > > swap. Writing "all" will allow all swap devices. > > I consider this conceptually cleaner than the "zswap.writeback" =3D=3D = 0 > > will also disable other swap types behavior. "disabled zswap writeback > > =3D=3D disable all swap" feels less natural. > > I implement a minimal version of the "swap.tiers" to replace the "zswap.w= riteback". > It only implements the ABI level. Under the hook it is using the writebac= k bool. > > This patch builds on top of your V5 patch. > > implement memory.swap.tiers on top of memory.zswap.writeback. > > "memory.swap.tiers" supports two key words for now: > all: all swap swap tiers are considered. (previously zswap.writback =3D= =3D 1) > zswap: only zswap tier are considered. (previously zswap.writeback =3D=3D= 0) > > Index: linux/mm/memcontrol.c > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > --- linux.orig/mm/memcontrol.c > +++ linux/mm/memcontrol.c > @@ -7992,6 +7992,32 @@ static int swap_events_show(struct seq_f > return 0; > } > > +static int swap_tiers_show(struct seq_file *m, void *v) > +{ > + struct mem_cgroup *memcg =3D mem_cgroup_from_seq(m); > + > + seq_printf(m, "%s\n", READ_ONCE(memcg->zswap_writeback) ? "all" := "zswap"); > + return 0; > +} > + > +static ssize_t swap_tiers_write(struct kernfs_open_file *of, > + char *buf, size_t nbytes, loff_t off) > +{ > + struct mem_cgroup *memcg =3D mem_cgroup_from_css(of_css(of)); > + int zswap_writeback; > + > + buf =3D strstrip(buf); > + if (!strcmp(buf, "all")) > + zswap_writeback =3D 1; > + else if (!strcmp(buf, "zswap")) > + zswap_writeback =3D 0; > + else > + return -EINVAL; > + > + WRITE_ONCE(memcg->zswap_writeback, zswap_writeback); > + return nbytes; > +} > + > static struct cftype swap_files[] =3D { > { > .name =3D "swap.current", > @@ -8021,6 +8047,12 @@ static struct cftype swap_files[] =3D { > .file_offset =3D offsetof(struct mem_cgroup, swap_events_= file), > .seq_show =3D swap_events_show, > }, > + { > + .name =3D "swap.tiers", > + .seq_show =3D swap_tiers_show, > + .write =3D swap_tiers_write, > + }, > + > { } /* terminate */ > }; > > @@ -8183,31 +8215,6 @@ static ssize_t zswap_max_write(struct ke > return nbytes; > } > > -static int zswap_writeback_show(struct seq_file *m, void *v) > -{ > - struct mem_cgroup *memcg =3D mem_cgroup_from_seq(m); > - > - seq_printf(m, "%d\n", READ_ONCE(memcg->zswap_writeback)); > - return 0; > -} > - > -static ssize_t zswap_writeback_write(struct kernfs_open_file *of, > - char *buf, size_t nbytes, loff_t off) > -{ > - struct mem_cgroup *memcg =3D mem_cgroup_from_css(of_css(of)); > - int zswap_writeback; > - ssize_t parse_ret =3D kstrtoint(strstrip(buf), 0, &zswap_writebac= k); > - > - if (parse_ret) > - return parse_ret; > - > - if (zswap_writeback !=3D 0 && zswap_writeback !=3D 1) > - return -EINVAL; > - > - WRITE_ONCE(memcg->zswap_writeback, zswap_writeback); > - return nbytes; > -} > - > static struct cftype zswap_files[] =3D { > { > .name =3D "zswap.current", > @@ -8220,11 +8227,6 @@ static struct cftype zswap_files[] =3D { > .seq_show =3D zswap_max_show, > .write =3D zswap_max_write, > }, > - { > - .name =3D "zswap.writeback", > - .seq_show =3D zswap_writeback_show, > - .write =3D zswap_writeback_write, > - }, > { } /* terminate */ > }; > #endif /* CONFIG_MEMCG_KMEM && CONFIG_ZSWAP */ Hi Chris! Thanks for the patch. Would you mind if I spend some time staring at the suggestion again and testing it some more? If everything is good, I'll squash this patch with the original version, (keeping you as a co-developer of the final patch of course), and update the documentation before re-sending everything as v6. Anyway, have a nice Thanksgiving break everyone! Thanks for taking the time to review my patch and discuss the API with me!