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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED autolearn=ham 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 B9880C433B4 for ; Mon, 10 May 2021 04:32:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 968B761040 for ; Mon, 10 May 2021 04:32:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229953AbhEJEdT (ORCPT ); Mon, 10 May 2021 00:33:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:37074 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229533AbhEJEdT (ORCPT ); Mon, 10 May 2021 00:33:19 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id DA693610CA; Mon, 10 May 2021 04:32:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620621135; bh=r6V0wu6fjdnNRmElY/sp6GLpKKEBo4jI/fnNcEcrFwA=; h=Date:From:To:Subject:From; b=2t1TsapQGS3lEKE24EJc98wCgfcfqO1vTF4HZnDbujGZOhloT4ub0w9g2AsS0QSSp PT4xIfvH3OgzQWvWK5q33/znE67jrFXcq0yQOjttrTaCBgaM4kWWjiHZ9rG3FH4L2H SMrM/WRXVWZ/1xUlT87GzWRt03DwBZ7t47RX406w= Date: Sun, 09 May 2021 21:32:14 -0700 From: akpm@linux-foundation.org To: duanxiongchun@bytedance.com, guro@fb.com, hannes@cmpxchg.org, mhocko@suse.com, mm-commits@vger.kernel.org, shakeelb@google.com, songmuchun@bytedance.com, vdavydov.dev@gmail.com Subject: + mm-memcontrol-simplify-the-logic-of-objcg-pinning-memcg.patch added to -mm tree Message-ID: <20210510043214.XWAJXl444%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm: memcontrol: simplify the logic of objcg pinning memcg has been added to the -mm tree. Its filename is mm-memcontrol-simplify-the-logic-of-objcg-pinning-memcg.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-memcontrol-simplify-the-logic-of-objcg-pinning-memcg.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcontrol-simplify-the-logic-of-objcg-pinning-memcg.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Muchun Song Subject: mm: memcontrol: simplify the logic of objcg pinning memcg The obj_cgroup_release() and memcg_reparent_objcgs() are serialized by the css_set_lock. We do not need to care about objcg->memcg being released in the process of obj_cgroup_release(). So there is no need to pin memcg before releasing objcg. Remove those pinning logic to simplfy the code. There are only two places that modifies the objcg->memcg. One is the initialization to objcg->memcg in the memcg_online_kmem(), another is objcgs reparenting in the memcg_reparent_objcgs(). It is also impossible for the two to run in parallel. So xchg() is unnecessary and it is enough to use WRITE_ONCE(). Link: https://lkml.kernel.org/r/20210417043538.9793-7-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Johannes Weiner Reviewed-by: Shakeel Butt Acked-by: Roman Gushchin Cc: Michal Hocko Cc: Vladimir Davydov Cc: Xiongchun Duan Signed-off-by: Andrew Morton --- mm/memcontrol.c | 20 ++++++-------------- 1 file changed, 6 insertions(+), 14 deletions(-) --- a/mm/memcontrol.c~mm-memcontrol-simplify-the-logic-of-objcg-pinning-memcg +++ a/mm/memcontrol.c @@ -261,7 +261,6 @@ static void obj_cgroup_uncharge_pages(st static void obj_cgroup_release(struct percpu_ref *ref) { struct obj_cgroup *objcg = container_of(ref, struct obj_cgroup, refcnt); - struct mem_cgroup *memcg; unsigned int nr_bytes; unsigned int nr_pages; unsigned long flags; @@ -291,11 +290,9 @@ static void obj_cgroup_release(struct pe nr_pages = nr_bytes >> PAGE_SHIFT; spin_lock_irqsave(&css_set_lock, flags); - memcg = obj_cgroup_memcg(objcg); if (nr_pages) obj_cgroup_uncharge_pages(objcg, nr_pages); list_del(&objcg->list); - mem_cgroup_put(memcg); spin_unlock_irqrestore(&css_set_lock, flags); percpu_ref_exit(ref); @@ -330,17 +327,12 @@ static void memcg_reparent_objcgs(struct spin_lock_irq(&css_set_lock); - /* Move active objcg to the parent's list */ - xchg(&objcg->memcg, parent); - css_get(&parent->css); - list_add(&objcg->list, &parent->objcg_list); - - /* Move already reparented objcgs to the parent's list */ - list_for_each_entry(iter, &memcg->objcg_list, list) { - css_get(&parent->css); - xchg(&iter->memcg, parent); - css_put(&memcg->css); - } + /* 1) Ready to reparent active objcg. */ + list_add(&objcg->list, &memcg->objcg_list); + /* 2) Reparent active objcg and already reparented objcgs to parent. */ + list_for_each_entry(iter, &memcg->objcg_list, list) + WRITE_ONCE(iter->memcg, parent); + /* 3) Move already reparented objcgs to the parent's list */ list_splice(&memcg->objcg_list, &parent->objcg_list); spin_unlock_irq(&css_set_lock); _ Patches currently in -mm which might be from songmuchun@bytedance.com are mm-memcontrol-fix-root_mem_cgroup-charging.patch mm-memcontrol-fix-page-charging-in-page-replacement.patch mm-memcontrol-bail-out-early-when-mm-in-get_mem_cgroup_from_mm.patch mm-memcontrol-remove-the-pgdata-parameter-of-mem_cgroup_page_lruvec.patch mm-memcontrol-simplify-lruvec_holds_page_lru_lock.patch mm-memcontrol-rename-lruvec_holds_page_lru_lock-to-page_matches_lruvec.patch mm-memcontrol-simplify-the-logic-of-objcg-pinning-memcg.patch mm-memcontrol-move-obj_cgroup_uncharge_pages-out-of-css_set_lock.patch mm-vmscan-remove-noinline_for_stack.patch mm-memory_hotplug-factor-out-bootmem-core-functions-to-bootmem_infoc.patch mm-hugetlb-introduce-a-new-config-hugetlb_page_free_vmemmap.patch mm-hugetlb-gather-discrete-indexes-of-tail-page.patch mm-hugetlb-free-the-vmemmap-pages-associated-with-each-hugetlb-page.patch mm-hugetlb-defer-freeing-of-hugetlb-pages.patch mm-hugetlb-alloc-the-vmemmap-pages-associated-with-each-hugetlb-page.patch mm-hugetlb-add-a-kernel-parameter-hugetlb_free_vmemmap.patch mm-memory_hotplug-disable-memmap_on_memory-when-hugetlb_free_vmemmap-enabled.patch mm-hugetlb-introduce-nr_free_vmemmap_pages-in-the-struct-hstate.patch