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d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=GC0X1A1u34H3gu6Exp5dVJ6e1IpoU2YLjA8YbGTqXlw=; b=NyNyZAxjVVfKe5NRCuOh/tuC/JMoPkHEB07XJ9E/pXpbjEtvFD/Xa4NFnjk4TRyXZy hDX0t4jmspxd/JyLES0BysDKnqVlZI4vi4eQd64GLL31MZMx7rej1k0S4DozzRRJHM/z Vs5oIIZM9HLM7fB46G604OGgsijwn8iBuMekq/erabGTgg9I+csOOBNvi1b+8lpmGE3e HQB27gqlCWuUfDvjD9ID5eBLQNaTVQrM0VgOGEl7M/VnB6PXodQeZxN0w02UDbDMsVXm pixaZitUg9gPTTYcdB1aNHXeKTNYWO4n8CPop1eggW0nCYQvHfC1Y3tVC0BfoxlWrn28 9G3A== X-Gm-Message-State: AOAM531Nl4zr9N9F30N3vey4Ian6fX6HYtO0tTTxVDVw27Y5fD46hbvn snTo3Z756L2lCjoSySSEJzMlnQ0nX6PgIh1ONKiAjQ== X-Google-Smtp-Source: ABdhPJwpvTKkWRXgxu6zXw3WSGE6mJFBDibW77din/FtDcY/O0Rnc79GZLGHzqU1j9mW/Df+g6149erumhq14TW0lEE= X-Received: by 2002:a2e:a58a:: with SMTP id m10mr3091893ljp.347.1592613115441; Fri, 19 Jun 2020 17:31:55 -0700 (PDT) MIME-Version: 1.0 References: <20200608230654.828134-1-guro@fb.com> <20200608230654.828134-8-guro@fb.com> <20200620002513.GD237539@carbon.dhcp.thefacebook.com> In-Reply-To: <20200620002513.GD237539@carbon.dhcp.thefacebook.com> From: Shakeel Butt Date: Fri, 19 Jun 2020 17:31:44 -0700 Message-ID: Subject: Re: [PATCH v6 07/19] mm: memcg/slab: allocate obj_cgroups for non-root slab pages To: Roman Gushchin Cc: Andrew Morton , Christoph Lameter , Johannes Weiner , Michal Hocko , Linux MM , Vlastimil Babka , Kernel Team , LKML Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: A560018026118 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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: On Fri, Jun 19, 2020 at 5:25 PM Roman Gushchin wrote: > > On Fri, Jun 19, 2020 at 09:36:16AM -0700, Shakeel Butt wrote: > > On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin wrote: > > > > > > Allocate and release memory to store obj_cgroup pointers for each > > > non-root slab page. Reuse page->mem_cgroup pointer to store a pointer > > > to the allocated space. > > > > > > To distinguish between obj_cgroups and memcg pointers in case > > > when it's not obvious which one is used (as in page_cgroup_ino()), > > > let's always set the lowest bit in the obj_cgroup case. > > > > > > > I think the commit message should talk about the potential overhead > > (i.e an extra pointer for each object) along with the justifications > > (i.e. less internal fragmentation and potentially more savings than > > the overhead). > > How about adding the following chunk? I don't like forward links in > commit messages, so maybe putting it into the cover letter? > > This commit temporarily increases the memory footprint of the kernel memory > accounting. To store obj_cgroup pointers we'll need a place for an > objcg_pointer for each allocated object. However, the following patches > in the series will enable sharing of slab pages between memory cgroups, > which will dramatically increase the total slab utilization. And the final > memory footprint will be significantly smaller than before. > This looks good to me. > > > > > Signed-off-by: Roman Gushchin > > > Reviewed-by: Vlastimil Babka > > > --- > > > include/linux/mm_types.h | 5 +++- > > > include/linux/slab_def.h | 6 +++++ > > > include/linux/slub_def.h | 5 ++++ > > > mm/memcontrol.c | 17 +++++++++++--- > > > mm/slab.h | 49 ++++++++++++++++++++++++++++++++++++++++ > > > 5 files changed, 78 insertions(+), 4 deletions(-) > > > > > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > > > index 64ede5f150dc..0277fbab7c93 100644 > > > --- a/include/linux/mm_types.h > > > +++ b/include/linux/mm_types.h > > > @@ -198,7 +198,10 @@ struct page { > > > atomic_t _refcount; > > > > > > #ifdef CONFIG_MEMCG > > > - struct mem_cgroup *mem_cgroup; > > > + union { > > > + struct mem_cgroup *mem_cgroup; > > > + struct obj_cgroup **obj_cgroups; > > > + }; > > > #endif > > > > > > /* > > > diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h > > > index abc7de77b988..ccda7b9669a5 100644 > > > --- a/include/linux/slab_def.h > > > +++ b/include/linux/slab_def.h > > > @@ -114,4 +114,10 @@ static inline unsigned int obj_to_index(const struct kmem_cache *cache, > > > return reciprocal_divide(offset, cache->reciprocal_buffer_size); > > > } > > > > > > +static inline int objs_per_slab_page(const struct kmem_cache *cache, > > > + const struct page *page) > > > +{ > > > + return cache->num; > > > +} > > > + > > > #endif /* _LINUX_SLAB_DEF_H */ > > > diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h > > > index 30e91c83d401..f87302dcfe8c 100644 > > > --- a/include/linux/slub_def.h > > > +++ b/include/linux/slub_def.h > > > @@ -198,4 +198,9 @@ static inline unsigned int obj_to_index(const struct kmem_cache *cache, > > > return __obj_to_index(cache, page_address(page), obj); > > > } > > > > > > +static inline int objs_per_slab_page(const struct kmem_cache *cache, > > > + const struct page *page) > > > +{ > > > + return page->objects; > > > +} > > > #endif /* _LINUX_SLUB_DEF_H */ > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > > index 7ff66275966c..2020c7542aa1 100644 > > > --- a/mm/memcontrol.c > > > +++ b/mm/memcontrol.c > > > @@ -569,10 +569,21 @@ ino_t page_cgroup_ino(struct page *page) > > > unsigned long ino = 0; > > > > > > rcu_read_lock(); > > > - if (PageSlab(page) && !PageTail(page)) > > > + if (PageSlab(page) && !PageTail(page)) { > > > memcg = memcg_from_slab_page(page); > > > - else > > > - memcg = READ_ONCE(page->mem_cgroup); > > > + } else { > > > + memcg = page->mem_cgroup; > > > + > > > + /* > > > + * The lowest bit set means that memcg isn't a valid > > > + * memcg pointer, but a obj_cgroups pointer. > > > + * In this case the page is shared and doesn't belong > > > + * to any specific memory cgroup. > > > + */ > > > + if ((unsigned long) memcg & 0x1UL) > > > + memcg = NULL; > > > + } > > > + > > > while (memcg && !(memcg->css.flags & CSS_ONLINE)) > > > memcg = parent_mem_cgroup(memcg); > > > if (memcg) > > > diff --git a/mm/slab.h b/mm/slab.h > > > index 8a574d9361c1..a1633ea15fbf 100644 > > > --- a/mm/slab.h > > > +++ b/mm/slab.h > > > @@ -319,6 +319,18 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s) > > > return s->memcg_params.root_cache; > > > } > > > > > > +static inline struct obj_cgroup **page_obj_cgroups(struct page *page) > > > +{ > > > + /* > > > + * page->mem_cgroup and page->obj_cgroups are sharing the same > > > + * space. To distinguish between them in case we don't know for sure > > > + * that the page is a slab page (e.g. page_cgroup_ino()), let's > > > + * always set the lowest bit of obj_cgroups. > > > + */ > > > + return (struct obj_cgroup **) > > > + ((unsigned long)page->obj_cgroups & ~0x1UL); > > > +} > > > + > > > /* > > > * Expects a pointer to a slab page. Please note, that PageSlab() check > > > * isn't sufficient, as it returns true also for tail compound slab pages, > > > @@ -406,6 +418,26 @@ static __always_inline void memcg_uncharge_slab(struct page *page, int order, > > > percpu_ref_put_many(&s->memcg_params.refcnt, nr_pages); > > > } > > > > > > +static inline int memcg_alloc_page_obj_cgroups(struct page *page, > > > + struct kmem_cache *s, gfp_t gfp) > > > +{ > > > + unsigned int objects = objs_per_slab_page(s, page); > > > + void *vec; > > > + > > > + vec = kcalloc(objects, sizeof(struct obj_cgroup *), gfp); > > > > Should the above allocation be on the same node as the page? > > Yeah, it's a clever idea. The following patch should do the trick. > Andrew, can you, please, squash this in? > > Thank you! > > Reviewed-by: Shakeel Butt > diff --git a/mm/slab.h b/mm/slab.h > index 0a31600a0f5c..2a036eefbd7e 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -233,7 +233,8 @@ static inline int memcg_alloc_page_obj_cgroups(struct page *page, > unsigned int objects = objs_per_slab_page(s, page); > void *vec; > > - vec = kcalloc(objects, sizeof(struct obj_cgroup *), gfp); > + vec = kcalloc_node(objects, sizeof(struct obj_cgroup *), gfp, > + page_to_nid(page)); > if (!vec) > return -ENOMEM; >