lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Tue, 13 Oct 2020 11:29:44 +0800 From: Muchun Song <songmuchun@...edance.com> To: Cong Wang <xiyou.wangcong@...il.com> Cc: Greg KH <gregkh@...uxfoundation.org>, rafael@...nel.org, "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Alexey Dobriyan <adobriyan@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, Eric Dumazet <edumazet@...gle.com>, Alexey Kuznetsov <kuznet@....inr.ac.ru>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, Steffen Klassert <steffen.klassert@...unet.com>, Herbert Xu <herbert@...dor.apana.org.au>, Shakeel Butt <shakeelb@...gle.com>, Will Deacon <will@...nel.org>, Michal Hocko <mhocko@...e.com>, Roman Gushchin <guro@...com>, Neil Brown <neilb@...e.de>, Mike Rapoport <rppt@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Feng Tang <feng.tang@...el.com>, Paolo Abeni <pabeni@...hat.com>, Willem de Bruijn <willemb@...gle.com>, Randy Dunlap <rdunlap@...radead.org>, Florian Westphal <fw@...len.de>, gustavoars@...nel.org, Pablo Neira Ayuso <pablo@...filter.org>, Dexuan Cui <decui@...rosoft.com>, Jakub Sitnicki <jakub@...udflare.com>, Peter Zijlstra <peterz@...radead.org>, Christian Brauner <christian.brauner@...ntu.com>, "Eric W. Biederman" <ebiederm@...ssion.com>, Thomas Gleixner <tglx@...utronix.de>, dave@...olabs.net, Michel Lespinasse <walken@...gle.com>, Jann Horn <jannh@...gle.com>, chenqiwu@...omi.com, christophe.leroy@....fr, Minchan Kim <minchan@...nel.org>, Martin KaFai Lau <kafai@...com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Miaohe Lin <linmiaohe@...wei.com>, Kees Cook <keescook@...omium.org>, LKML <linux-kernel@...r.kernel.org>, virtualization@...ts.linux-foundation.org, Linux Kernel Network Developers <netdev@...r.kernel.org>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, linux-mm <linux-mm@...ck.org> Subject: Re: [External] Re: [PATCH] mm: proc: add Sock to /proc/meminfo On Tue, Oct 13, 2020 at 5:47 AM Cong Wang <xiyou.wangcong@...il.com> wrote: > > On Sun, Oct 11, 2020 at 9:22 PM Muchun Song <songmuchun@...edance.com> wrote: > > > > On Mon, Oct 12, 2020 at 2:39 AM Cong Wang <xiyou.wangcong@...il.com> wrote: > > > > > > On Sat, Oct 10, 2020 at 3:39 AM Muchun Song <songmuchun@...edance.com> wrote: > > > > > > > > The amount of memory allocated to sockets buffer can become significant. > > > > However, we do not display the amount of memory consumed by sockets > > > > buffer. In this case, knowing where the memory is consumed by the kernel > > > > > > We do it via `ss -m`. Is it not sufficient? And if not, why not adding it there > > > rather than /proc/meminfo? > > > > If the system has little free memory, we can know where the memory is via > > /proc/meminfo. If a lot of memory is consumed by socket buffer, we cannot > > know it when the Sock is not shown in the /proc/meminfo. If the unaware user > > can't think of the socket buffer, naturally they will not `ss -m`. The > > end result > > Interesting, we already have a few counters related to socket buffers, > are you saying these are not accounted in /proc/meminfo either? Yeah, these are not accounted for in /proc/meminfo. > If yes, why are page frags so special here? If not, they are more > important than page frags, so you probably want to deal with them > first. > > > > is that we still don’t know where the memory is consumed. And we add the > > Sock to the /proc/meminfo just like the memcg does('sock' item in the cgroup > > v2 memory.stat). So I think that adding to /proc/meminfo is sufficient. > > It looks like actually the socket page frag is already accounted, > for example, the tcp_sendmsg_locked(): > > copy = min_t(int, copy, pfrag->size - pfrag->offset); > > if (!sk_wmem_schedule(sk, copy)) > goto wait_for_memory; > Yeah, it is already accounted for. But it does not represent real memory usage. This is just the total amount of charged memory. For example, if a task sends a 10-byte message, it only charges one page to memcg. But the system may allocate 8 pages. Therefore, it does not truly reflect the memory allocated by the page frag memory allocation path. > > > > > > > > > > static inline void __skb_frag_unref(skb_frag_t *frag) > > > > { > > > > - put_page(skb_frag_page(frag)); > > > > + struct page *page = skb_frag_page(frag); > > > > + > > > > + if (put_page_testzero(page)) { > > > > + dec_sock_node_page_state(page); > > > > + __put_page(page); > > > > + } > > > > } > > > > > > You mix socket page frag with skb frag at least, not sure this is exactly > > > what you want, because clearly skb page frags are frequently used > > > by network drivers rather than sockets. > > > > > > Also, which one matches this dec_sock_node_page_state()? Clearly > > > not skb_fill_page_desc() or __skb_frag_ref(). > > > > Yeah, we call inc_sock_node_page_state() in the skb_page_frag_refill(). > > How is skb_page_frag_refill() possibly paired with __skb_frag_unref()? > > > So if someone gets the page returned by skb_page_frag_refill(), it must > > put the page via __skb_frag_unref()/skb_frag_unref(). We use PG_private > > to indicate that we need to dec the node page state when the refcount of > > page reaches zero. > > skb_page_frag_refill() is called on frags not within an skb, for instance, > sk_page_frag_refill() uses it for a per-socket or per-process page frag. > But, __skb_frag_unref() is specifically used for skb frags, which are > supposed to be filled by skb_fill_page_desc() (page is allocated by driver). > > They are different things you are mixing them up, which looks clearly > wrong or at least misleading. Yeah, it looks a little strange. I just want to account for page frag allocations. So I have to use PG_private to distinguish the page from page frag or others in the __skb_frag_unref(). If the page is allocated from skb_page_frag_refill, we should decrease the statistics. Thanks. > > Thanks. -- Yours, Muchun
Powered by blists - more mailing lists