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=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL 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 971B7C433E0 for ; Tue, 12 Jan 2021 23:37:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 587282312F for ; Tue, 12 Jan 2021 23:37:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404001AbhALXhM (ORCPT ); Tue, 12 Jan 2021 18:37:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42812 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389010AbhALXhL (ORCPT ); Tue, 12 Jan 2021 18:37:11 -0500 Received: from mail-pf1-x42e.google.com (mail-pf1-x42e.google.com [IPv6:2607:f8b0:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB879C061575 for ; Tue, 12 Jan 2021 15:36:30 -0800 (PST) Received: by mail-pf1-x42e.google.com with SMTP id m6so76005pfk.1 for ; Tue, 12 Jan 2021 15:36:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=mEBkOPFW86VPUoCBn9m9fpzpE6sqvzaVXLvlkeB1JaA=; b=UhsCzBkT0GLtG0z8nOtx7zVsEqDFaz2KKP/XtsMOT0Qnl10vOiacfrgKfGl4l8uWXA JxmxX/JcdwS6TWBHbtFkaHEGscp2l1eviDyldmuESpZTgmSuzL3sIA9E+/s32UoAXX7X +SeI5muVXqMZ8tbs/EJ5VWTrQ5eSWncDhujkb4QLozKP4HQ+pqPgACTOX7Xfm65SpSw/ LMzfrxyiBElteGS+5fQDLwsRw/T7KoU5mseo3h4ZsZ7SOL8fk8yJlcqc57iRo6waJykT tjit2miQOh67KTApCMsD7GQrbD7vT+qiK00zZf/ZTLNg72AVrGkKhMK4KlZrFpteWmv3 D6Uw== 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=mEBkOPFW86VPUoCBn9m9fpzpE6sqvzaVXLvlkeB1JaA=; b=AQvoYl2emWx2MjxBEz5SegrXxrAuVAqqbrsup0GFE//1dfnn+/I12fmglliSIB8ugR 2Qih2evT26aHfxkC3QTgWjKV+yASMrelo7lWvNh6sc4reRAgT1813yY+/KIMO3YIjjGz LzvTexq+yKvVrIfhaoyO6NyM4vlnhIA4KBtiB5rrgAHa/V1CxwZXgGgrQArN1N+DMmQM VGWTawE2H7RcsJIKnG0oRxYC8DxUCcoub7tSY0oIFjYtLbZfddhURYA26VO62YNs3fO4 NkWXrcc0uOKTD2ZPgGZ7h4Q/igYgE5MmY3b6fYENZISamb7j2fwJ9zDCJkvnL8pfPGLm 6nYQ== X-Gm-Message-State: AOAM5312FDhsp2rFDnEj/PXRomEx32mWX08fZjYq8vsAd/4KunNDu7qx if6j1Ppv1hclmdEPxEGMUpge3ReMXgoFOHMwSV8OH6uld0dPgA== X-Google-Smtp-Source: ABdhPJyk5PEF5UHB0B/0evvZXyll9soXfX1sZqruCPvrTzK6detAZyOBlgZXFnC2GV/AFSRanyOMa+5wpsm5ETLC9r8= X-Received: by 2002:a63:e:: with SMTP id 14mr1421869pga.253.1610494590037; Tue, 12 Jan 2021 15:36:30 -0800 (PST) MIME-Version: 1.0 References: <20210112214105.1440932-1-shakeelb@google.com> <20210112233108.GD99586@carbon.dhcp.thefacebook.com> In-Reply-To: <20210112233108.GD99586@carbon.dhcp.thefacebook.com> From: Arjun Roy Date: Tue, 12 Jan 2021 15:36:18 -0800 Message-ID: Subject: Re: [PATCH] mm: net: memcg accounting for TCP rx zerocopy To: Roman Gushchin Cc: Shakeel Butt , Johannes Weiner , Michal Hocko , Eric Dumazet , Andrew Morton , "David S . Miller" , Jakub Kicinski , linux-mm@kvack.org, cgroups@vger.kernel.org, netdev , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 12, 2021 at 3:31 PM Roman Gushchin wrote: > > On Tue, Jan 12, 2021 at 01:41:05PM -0800, Shakeel Butt wrote: > > From: Arjun Roy > > > > TCP zerocopy receive is used by high performance network applications to > > further scale. For RX zerocopy, the memory containing the network data > > filled by network driver is directly mapped into the address space of > > high performance applications. To keep the TLB cost low, these > > applications unmaps the network memory in big batches. So, this memory > > can remain mapped for long time. This can cause memory isolation issue > > as this memory becomes unaccounted after getting mapped into the > > application address space. This patch adds the memcg accounting for such > > memory. > > > > Accounting the network memory comes with its own unique challenge. The > > high performance NIC drivers use page pooling to reuse the pages to > > eliminate/reduce the expensive setup steps like IOMMU. These drivers > > keep an extra reference on the pages and thus we can not depends on the > > page reference for the uncharging. The page in the pool may keep a memcg > > pinned for arbitrary long time or may get used by other memcg. > > > > This patch decouples the uncharging of the page from the refcnt and > > associate it with the map count i.e. the page gets uncharged when the > > last address space unmaps it. Now the question what if the driver drops > > its reference while the page is still mapped. That is fine as the > > address space also holds a reference to the page i.e. the reference > > count can not drop to zero before the map count. > > > > Signed-off-by: Arjun Roy > > Co-developed-by: Shakeel Butt > > Signed-off-by: Shakeel Butt > > --- > > include/linux/memcontrol.h | 34 +++++++++++++++++++-- > > mm/memcontrol.c | 60 ++++++++++++++++++++++++++++++++++++++ > > mm/rmap.c | 3 ++ > > net/ipv4/tcp.c | 27 +++++++++++++---- > > 4 files changed, 116 insertions(+), 8 deletions(-) > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > index 7a38a1517a05..0b0e3b4615cf 100644 > > --- a/include/linux/memcontrol.h > > +++ b/include/linux/memcontrol.h > > @@ -349,11 +349,13 @@ extern struct mem_cgroup *root_mem_cgroup; > > > > enum page_memcg_data_flags { > > /* page->memcg_data is a pointer to an objcgs vector */ > > - MEMCG_DATA_OBJCGS = (1UL << 0), > > + MEMCG_DATA_OBJCGS = (1UL << 0), > > /* page has been accounted as a non-slab kernel page */ > > - MEMCG_DATA_KMEM = (1UL << 1), > > + MEMCG_DATA_KMEM = (1UL << 1), > > + /* page has been accounted as network memory */ > > + MEMCG_DATA_SOCK = (1UL << 2), > > /* the next bit after the last actual flag */ > > - __NR_MEMCG_DATA_FLAGS = (1UL << 2), > > + __NR_MEMCG_DATA_FLAGS = (1UL << 3), > > }; > > > > #define MEMCG_DATA_FLAGS_MASK (__NR_MEMCG_DATA_FLAGS - 1) > > @@ -444,6 +446,11 @@ static inline bool PageMemcgKmem(struct page *page) > > return page->memcg_data & MEMCG_DATA_KMEM; > > } > > > > +static inline bool PageMemcgSock(struct page *page) > > +{ > > + return page->memcg_data & MEMCG_DATA_SOCK; > > +} > > + > > #ifdef CONFIG_MEMCG_KMEM > > /* > > * page_objcgs - get the object cgroups vector associated with a page > > @@ -1095,6 +1102,11 @@ static inline bool PageMemcgKmem(struct page *page) > > return false; > > } > > > > +static inline bool PageMemcgSock(struct page *page) > > +{ > > + return false; > > +} > > + > > static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg) > > { > > return true; > > @@ -1561,6 +1573,10 @@ extern struct static_key_false memcg_sockets_enabled_key; > > #define mem_cgroup_sockets_enabled static_branch_unlikely(&memcg_sockets_enabled_key) > > void mem_cgroup_sk_alloc(struct sock *sk); > > void mem_cgroup_sk_free(struct sock *sk); > > +int mem_cgroup_charge_sock_pages(struct mem_cgroup *memcg, struct page **pages, > > + unsigned int nr_pages); > > +void mem_cgroup_uncharge_sock_pages(struct page **pages, unsigned int nr_pages); > > + > > static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg) > > { > > if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && memcg->tcpmem_pressure) > > @@ -1589,6 +1605,18 @@ static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg, > > int nid, int shrinker_id) > > { > > } > > + > > +static inline int mem_cgroup_charge_sock_pages(struct mem_cgroup *memcg, > > + struct page **pages, > > + unsigned int nr_pages) > > +{ > > + return 0; > > +} > > + > > +static inline void mem_cgroup_uncharge_sock_pages(struct page **pages, > > + unsigned int nr_pages) > > +{ > > +} > > #endif > > > > #ifdef CONFIG_MEMCG_KMEM > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index db9836f4b64b..38e94538e081 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -7061,6 +7061,66 @@ void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages) > > refill_stock(memcg, nr_pages); > > } > > > > +/** > > + * mem_cgroup_charge_sock_pages - charge socket memory > > + * @memcg: memcg to charge > > + * @pages: array of pages to charge > > + * @nr_pages: number of pages > > + * > > + * Charges all @pages to current's memcg. The caller should have a reference on > > + * the given memcg. > > + * > > + * Returns 0 on success. > > + */ > > +int mem_cgroup_charge_sock_pages(struct mem_cgroup *memcg, struct page **pages, > > + unsigned int nr_pages) > > +{ > > + int ret = 0; > > + > > + if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg)) > > + goto out; > > + > > + ret = try_charge(memcg, GFP_KERNEL, nr_pages); > > + > > + if (!ret) { > > + int i; > > + > > + for (i = 0; i < nr_pages; i++) > > + pages[i]->memcg_data = (unsigned long)memcg | > > + MEMCG_DATA_SOCK; > > + css_get_many(&memcg->css, nr_pages); > > + } > > +out: > > + return ret; > > +} > > + > > +/** > > + * mem_cgroup_uncharge_sock_pages - uncharge socket pages > > + * @pages: array of pages to uncharge > > + * @nr_pages: number of pages > > + * > > + * This assumes all pages are charged to the same memcg. > > + */ > > +void mem_cgroup_uncharge_sock_pages(struct page **pages, unsigned int nr_pages) > > +{ > > + int i; > > + struct mem_cgroup *memcg; > > + > > + if (mem_cgroup_disabled()) > > + return; > > + > > + memcg = page_memcg(pages[0]); > > + > > + if (unlikely(!memcg)) > > + return; > > + > > + refill_stock(memcg, nr_pages); > > + > > + for (i = 0; i < nr_pages; i++) > > + pages[i]->memcg_data = 0; > > + css_put_many(&memcg->css, nr_pages); > > +} > > What about statistics? Should it be accounted towards "sock", "slab/kmem" or deserves > a separate counter? Do we plan to eventually have shrinkers for this type of memory? > While the pages in question are part of an sk_buff, they may be accounted towards sockmem. However, that charge is unaccounted when the skb is freed after the receive operation. When they are in use by the user application I do not think sockmem is the right place to have a break-out counter. To double check, what do you mean by shrinker? > Two functions above do not contain anything network-related, > except the MEMCG_DATA_SOCK flag. Can it be merged with the kmem charging path? > > Code-wise the patch looks good to me. > > Thanks!