From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2D20CC4360C for ; Tue, 2 Mar 2021 08:50:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 04C1164DE4 for ; Tue, 2 Mar 2021 08:50:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1381896AbhCBIrV (ORCPT ); Tue, 2 Mar 2021 03:47:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1446188AbhCBDE2 (ORCPT ); Mon, 1 Mar 2021 22:04:28 -0500 Received: from mail-pj1-x1034.google.com (mail-pj1-x1034.google.com [IPv6:2607:f8b0:4864:20::1034]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A71AC06178B for ; Mon, 1 Mar 2021 19:03:42 -0800 (PST) Received: by mail-pj1-x1034.google.com with SMTP id d13-20020a17090abf8db02900c0590648b1so502009pjs.1 for ; Mon, 01 Mar 2021 19:03:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=1bhqnALZ2+KE5BNt1x/b9t2x1AkPvkj58NfI+kSCMY8=; b=UYnhJBpLGeXBzTsG1LRoT9PKDmaTMwK9UVmBSKewIAouqErxx2ofVXdE+eXziIbdpd sGoirzJpSJXD/iCzCesUzihCGoEtLPB5MgPV1zx3ZlDdMeVTHur4f+XAPZ+P/Xp2I050 4AGVuC3F0W9MqITV+2Vh0iABS/bLWKy/hxLNu+nn470erji9VMW/mDFTGDbRlB6fuWov o6s4PQooVOtr4HNnNIgMxpRUI0p3tTaywvWy4beq4Hkl67xSc/YbhKve+rR984OE/GFL 5L3Ua6Vx4i/C3mJ4O858u4zkNv5IHuaNTi2e9FuHOaenQwl3BW2OE/EOaLWKb2sT/Pag qDlQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1bhqnALZ2+KE5BNt1x/b9t2x1AkPvkj58NfI+kSCMY8=; b=AJ4xhR6BT4L9sp3YAa+sWcVry9ottTtzIL1sxTdhsOPUNJlwcnpqvXUnmt94CMEiO2 TE9ousr3PY9PE7Kk1Q3JJyoId+GoL2gRPmLI3NbqwFWAU2vDUvq6RR1a6mhJZGyLMlC3 Jw7X/jWk+I3cjPf+mLUkJiriyvxBEAO7KssgscML7bS0EgInD4fFbvKzzVZfJvmQxH/C EOHTLJ03OAhdoFIV3SDDdm2Y3+a/Zz7GZ9fNmXTlfsJprzUAa3wP269WZOC1AH2eqLDd BdAO2s0JOrKy5OVJRWHLcnBAOLduUw49iggWbqO9mjTEqjxD2Y1pCOTj550J26Xy0zGY jQuw== X-Gm-Message-State: AOAM531+R8WIgtPixvppyeFtxZdeIPuOpGB7FbjapZ2LwoNlPWP/tGDL X5Zc2fVeuQYSkd69JnoobXmSGko+nAveec+bi03fLQ== X-Google-Smtp-Source: ABdhPJzkDzVaKb6VAcUaPdmIqjsZ96Mht1x5iPUiMpXvga/HiZejji300KaqZif5tK9B32QsU9s1bkNMxlRSC7wGZyk= X-Received: by 2002:a17:902:9341:b029:e1:7b4e:57a8 with SMTP id g1-20020a1709029341b02900e17b4e57a8mr1633790plp.34.1614654221758; Mon, 01 Mar 2021 19:03:41 -0800 (PST) MIME-Version: 1.0 References: <20210301062227.59292-1-songmuchun@bytedance.com> <20210301062227.59292-3-songmuchun@bytedance.com> In-Reply-To: From: Muchun Song Date: Tue, 2 Mar 2021 11:03:05 +0800 Message-ID: Subject: Re: [External] Re: [PATCH 2/5] mm: memcontrol: make page_memcg{_rcu} only applicable for non-kmem page To: Shakeel Butt Cc: Alexander Viro , Jan Kara , Amir Goldstein , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , kpsingh@kernel.org, Ingo Molnar , "Peter Zijlstra (Intel)" , Juri Lelli , Vincent Guittot , dietmar.eggemann@arm.com, Steven Rostedt , Benjamin Segall , Mel Gorman , bristot@redhat.com, Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Roman Gushchin , Alex Shi , Chris Down , Wei Yang , Vlastimil Babka , Mathieu Desnoyers , Peter Oskolkov , Jann Horn , Joonsoo Kim , Daniel Vetter , Waiman Long , Michel Lespinasse , Christian Brauner , "Eric W. Biederman" , Kees Cook , krisman@collabora.com, esyr@redhat.com, Suren Baghdasaryan , Marco Elver , linux-fsdevel , LKML , netdev , bpf , Cgroups , Linux MM , Xiongchun duan Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Mar 2, 2021 at 2:11 AM Shakeel Butt wrote: > > On Sun, Feb 28, 2021 at 10:25 PM Muchun Song wrote: > > > > We want to reuse the obj_cgroup APIs to reparent the kmem pages when > > the memcg offlined. If we do this, we should store an object cgroup > > pointer to page->memcg_data for the kmem pages. > > > > Finally, page->memcg_data can have 3 different meanings. > > > > 1) For the slab pages, page->memcg_data points to an object cgroups > > vector. > > > > 2) For the kmem pages (exclude the slab pages), page->memcg_data > > points to an object cgroup. > > > > 3) For the user pages (e.g. the LRU pages), page->memcg_data points > > to a memory cgroup. > > > > Currently we always get the memcg associated with a page via page_memcg > > or page_memcg_rcu. page_memcg_check is special, it has to be used in > > cases when it's not known if a page has an associated memory cgroup > > pointer or an object cgroups vector. Because the page->memcg_data of > > the kmem page is not pointing to a memory cgroup in the later patch, > > the page_memcg and page_memcg_rcu cannot be applicable for the kmem > > pages. In this patch, we introduce page_memcg_kmem to get the memcg > > associated with the kmem pages. And make page_memcg and page_memcg_rcu > > no longer apply to the kmem pages. > > > > In the end, there are 4 helpers to get the memcg associated with a > > page. The usage is as follows. > > > > 1) Get the memory cgroup associated with a non-kmem page (e.g. the LRU > > pages). > > > > - page_memcg() > > - page_memcg_rcu() > > Can you rename these to page_memcg_lru[_rcu] to make them explicitly > for LRU pages? Yes. Will do. Thanks. > > > > > 2) Get the memory cgroup associated with a kmem page (exclude the slab > > pages). > > > > - page_memcg_kmem() > > > > 3) Get the memory cgroup associated with a page. It has to be used in > > cases when it's not known if a page has an associated memory cgroup > > pointer or an object cgroups vector. Returns NULL for slab pages or > > uncharged pages, otherwise, returns memory cgroup for charged pages > > (e.g. kmem pages, LRU pages). > > > > - page_memcg_check() > > > > In some place, we use page_memcg to check whether the page is charged. > > Now we introduce page_memcg_charged helper to do this. > > > > This is a preparation for reparenting the kmem pages. To support reparent > > kmem pages, we just need to adjust page_memcg_kmem and page_memcg_check in > > the later patch. > > > > Signed-off-by: Muchun Song > > --- > [snip] > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -855,10 +855,11 @@ void __mod_lruvec_page_state(struct page *page, enum node_stat_item idx, > > int val) > > { > > struct page *head = compound_head(page); /* rmap on tail pages */ > > - struct mem_cgroup *memcg = page_memcg(head); > > + struct mem_cgroup *memcg; > > pg_data_t *pgdat = page_pgdat(page); > > struct lruvec *lruvec; > > > > + memcg = PageMemcgKmem(head) ? page_memcg_kmem(head) : page_memcg(head); > > Should page_memcg_check() be used here? Yeah. page_memcg_check() can be used here. But on the inside of the page_memcg_check(), there is a READ_ONCE(). Actually, we do not need READ_ONCE() here. So I use page_memcg or page_memcg_kmem directly. Thanks. > > > /* Untracked pages have no memcg, no lruvec. Update only the node */ > > if (!memcg) { > > __mod_node_page_state(pgdat, idx, val); > > @@ -3170,12 +3171,13 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order) > > */ > > void __memcg_kmem_uncharge_page(struct page *page, int order) > > { > > - struct mem_cgroup *memcg = page_memcg(page); > > + struct mem_cgroup *memcg; > > unsigned int nr_pages = 1 << order; > > > > - if (!memcg) > > + if (!page_memcg_charged(page)) > > return; > > > > + memcg = page_memcg_kmem(page); > > VM_BUG_ON_PAGE(mem_cgroup_is_root(memcg), page); > > __memcg_kmem_uncharge(memcg, nr_pages); > > page->memcg_data = 0; > > @@ -6831,24 +6833,25 @@ static void uncharge_batch(const struct uncharge_gather *ug) > > static void uncharge_page(struct page *page, struct uncharge_gather *ug) > > { > > unsigned long nr_pages; > > + struct mem_cgroup *memcg; > > > > VM_BUG_ON_PAGE(PageLRU(page), page); > > > > - if (!page_memcg(page)) > > + if (!page_memcg_charged(page)) > > return; > > > > /* > > * Nobody should be changing or seriously looking at > > - * page_memcg(page) at this point, we have fully > > - * exclusive access to the page. > > + * page memcg at this point, we have fully exclusive > > + * access to the page. > > */ > > - > > - if (ug->memcg != page_memcg(page)) { > > + memcg = PageMemcgKmem(page) ? page_memcg_kmem(page) : page_memcg(page); > > Same, should page_memcg_check() be used here? Same as above.