From: "Michal Koutný" <mkoutny@suse.com> To: Johannes Weiner <hannes@cmpxchg.org> Cc: Andrew Morton <akpm@linux-foundation.org>, Michal Hocko <mhocko@suse.com>, Roman Gushchin <guro@fb.com>, Shakeel Butt <shakeelb@google.com>, Seth Jennings <sjenning@redhat.com>, Dan Streetman <ddstreet@ieee.org>, Minchan Kim <minchan@kernel.org>, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH v2 6/6] zswap: memcg accounting Date: Fri, 13 May 2022 17:14:26 +0200 [thread overview] Message-ID: <20220513151426.GC16096@blackbody.suse.cz> (raw) In-Reply-To: <YnwJUL90fuoHs3YW@cmpxchg.org> On Wed, May 11, 2022 at 03:06:56PM -0400, Johannes Weiner <hannes@cmpxchg.org> wrote: > Correct. After which the uncompressed page is reclaimed and uncharged. > So the zswapout process will reduce the charge bottom line. A zswap object falling under memory.current was my first thinking, I was confused why it's exported as a separate counter memory.zswap.current (which IMO suggests disjoint counting) and it doubles a memory.stat:zswap entry. Is the separate memory.zswap.current good for anything? (Except maybe avoiding global rstat flush on memory.stat read but that'd be an undesired precendent.) (Ad the eventually reduced footprint, the transitional excursion above memcg's (or ancestor's) limit should be limited by number of parallel reclaims running (each one at most a page, right?), so it doesn't seem necessary to tackle (now).) > memory.zswap.* are there to configure zswap policy, within the > boundaries of available memory - it's by definition a subset. I see how the .max works when equal to 0 or "max". The intermediate values are more difficult to reason about. Also, I can see that on the global level, zswap is configured relatively (/sys/module/zswap/parameters/max_pool_percent). You wrote that the actual configured value is workload specific, would it be simpler to have also relative zswap limit per memcg? (Relative wrt memory.max, it'd be rather just a convenience with this simple ratio, however, it'd correspond to the top level limit. OTOH, the relatives would have counter-intuitive hierarchical behavior. I don't mean this should be changed, rather wondering why this variant was chosen.) > +bool obj_cgroup_may_zswap(struct obj_cgroup *objcg) > +{ > + struct mem_cgroup *memcg, *original_memcg; > + bool ret = true; > + > + original_memcg = get_mem_cgroup_from_objcg(objcg); > + for (memcg = original_memcg; memcg != root_mem_cgroup; > + memcg = parent_mem_cgroup(memcg)) { > + unsigned long max = READ_ONCE(memcg->zswap_max); > + unsigned long pages; > + > + if (max == PAGE_COUNTER_MAX) > + continue; > + if (max == 0) { > + ret = false; > + break; > + } > + > + cgroup_rstat_flush(memcg->css.cgroup); Here, I think it'd be better not to bypass mem_cgroup_flush_stats() (the mechanism is approximate and you traverse all ancestors anyway), i.e. mem_cgroup_flush_stats() before the loop instead of this. Thanks, Michal
WARNING: multiple messages have this Message-ID (diff)
From: "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org> To: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org> Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>, Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>, Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Seth Jennings <sjenning-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Dan Streetman <ddstreet-EkmVulN54Sk@public.gmane.org>, Minchan Kim <minchan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org Subject: Re: [PATCH v2 6/6] zswap: memcg accounting Date: Fri, 13 May 2022 17:14:26 +0200 [thread overview] Message-ID: <20220513151426.GC16096@blackbody.suse.cz> (raw) In-Reply-To: <YnwJUL90fuoHs3YW-druUgvl0LCNAfugRpC6u6w@public.gmane.org> On Wed, May 11, 2022 at 03:06:56PM -0400, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org> wrote: > Correct. After which the uncompressed page is reclaimed and uncharged. > So the zswapout process will reduce the charge bottom line. A zswap object falling under memory.current was my first thinking, I was confused why it's exported as a separate counter memory.zswap.current (which IMO suggests disjoint counting) and it doubles a memory.stat:zswap entry. Is the separate memory.zswap.current good for anything? (Except maybe avoiding global rstat flush on memory.stat read but that'd be an undesired precendent.) (Ad the eventually reduced footprint, the transitional excursion above memcg's (or ancestor's) limit should be limited by number of parallel reclaims running (each one at most a page, right?), so it doesn't seem necessary to tackle (now).) > memory.zswap.* are there to configure zswap policy, within the > boundaries of available memory - it's by definition a subset. I see how the .max works when equal to 0 or "max". The intermediate values are more difficult to reason about. Also, I can see that on the global level, zswap is configured relatively (/sys/module/zswap/parameters/max_pool_percent). You wrote that the actual configured value is workload specific, would it be simpler to have also relative zswap limit per memcg? (Relative wrt memory.max, it'd be rather just a convenience with this simple ratio, however, it'd correspond to the top level limit. OTOH, the relatives would have counter-intuitive hierarchical behavior. I don't mean this should be changed, rather wondering why this variant was chosen.) > +bool obj_cgroup_may_zswap(struct obj_cgroup *objcg) > +{ > + struct mem_cgroup *memcg, *original_memcg; > + bool ret = true; > + > + original_memcg = get_mem_cgroup_from_objcg(objcg); > + for (memcg = original_memcg; memcg != root_mem_cgroup; > + memcg = parent_mem_cgroup(memcg)) { > + unsigned long max = READ_ONCE(memcg->zswap_max); > + unsigned long pages; > + > + if (max == PAGE_COUNTER_MAX) > + continue; > + if (max == 0) { > + ret = false; > + break; > + } > + > + cgroup_rstat_flush(memcg->css.cgroup); Here, I think it'd be better not to bypass mem_cgroup_flush_stats() (the mechanism is approximate and you traverse all ancestors anyway), i.e. mem_cgroup_flush_stats() before the loop instead of this. Thanks, Michal
next prev parent reply other threads:[~2022-05-13 15:14 UTC|newest] Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-05-10 15:28 [PATCH v2 0/6] zswap: accounting & cgroup control Johannes Weiner 2022-05-10 15:28 ` Johannes Weiner 2022-05-10 15:28 ` [PATCH v2 1/6] Documentation: filesystems: proc: update meminfo section Johannes Weiner 2022-05-10 15:28 ` Johannes Weiner 2022-05-11 17:11 ` David Hildenbrand 2022-05-11 17:11 ` David Hildenbrand 2022-05-11 18:51 ` Johannes Weiner 2022-05-11 18:51 ` Johannes Weiner 2022-05-12 8:55 ` David Hildenbrand 2022-05-12 8:55 ` David Hildenbrand 2022-05-10 15:28 ` [PATCH v2 2/6] mm: Kconfig: move swap and slab config options to the MM section Johannes Weiner 2022-05-10 15:28 ` Johannes Weiner 2022-05-10 15:28 ` [PATCH v2 3/6] mm: Kconfig: group swap, slab, hotplug and thp options into submenus Johannes Weiner 2022-05-10 15:28 ` Johannes Weiner 2022-05-10 22:40 ` Andrew Morton 2022-05-10 22:40 ` Andrew Morton 2022-05-11 15:22 ` Johannes Weiner 2022-05-11 15:22 ` Johannes Weiner 2022-05-11 16:28 ` Johannes Weiner 2022-05-11 16:28 ` Johannes Weiner 2022-05-10 15:28 ` [PATCH v2 4/6] mm: Kconfig: simplify zswap configuration Johannes Weiner 2022-05-10 15:28 ` Johannes Weiner 2022-05-10 15:28 ` [PATCH v2 5/6] mm: zswap: add basic meminfo and vmstat coverage Johannes Weiner 2022-05-10 15:28 ` Johannes Weiner 2022-05-11 17:13 ` David Hildenbrand 2022-05-11 17:13 ` David Hildenbrand 2022-05-10 15:28 ` [PATCH v2 6/6] zswap: memcg accounting Johannes Weiner 2022-05-10 15:28 ` Johannes Weiner 2022-05-11 17:32 ` Michal Koutný 2022-05-11 17:32 ` Michal Koutný 2022-05-11 19:06 ` Johannes Weiner 2022-05-11 19:06 ` Johannes Weiner 2022-05-13 15:14 ` Michal Koutný [this message] 2022-05-13 15:14 ` Michal Koutný 2022-05-13 17:08 ` Johannes Weiner 2022-05-13 17:08 ` Johannes Weiner 2022-05-16 14:34 ` Michal Koutný 2022-05-16 14:34 ` Michal Koutný 2022-05-16 20:01 ` Johannes Weiner 2022-05-16 20:01 ` Johannes Weiner 2022-05-17 23:52 ` Andrew Morton 2022-05-18 8:23 ` Michal Koutný 2022-05-18 8:23 ` Michal Koutný 2022-05-13 17:23 ` Shakeel Butt 2022-05-13 17:23 ` Shakeel Butt 2022-05-13 18:25 ` Johannes Weiner 2022-05-13 18:25 ` Johannes Weiner
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20220513151426.GC16096@blackbody.suse.cz \ --to=mkoutny@suse.com \ --cc=akpm@linux-foundation.org \ --cc=cgroups@vger.kernel.org \ --cc=ddstreet@ieee.org \ --cc=guro@fb.com \ --cc=hannes@cmpxchg.org \ --cc=kernel-team@fb.com \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ --cc=mhocko@suse.com \ --cc=minchan@kernel.org \ --cc=shakeelb@google.com \ --cc=sjenning@redhat.com \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.