Re: [External] Re: [PATCH] mm: proc: add Sock to /proc/meminfo

Muchun Song
2020-10-11T16:01:05Z

On Sun, Oct 11, 2020 at 9:53 PM Mike Rapoport <rppt@kernel.org> wrote:
>
> On Sat, Oct 10, 2020 at 06:38:54PM +0800, Muchun Song 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
> > is very difficult. On our server with 500GB RAM, sometimes we can see
> > 25GB disappear through /proc/meminfo. After our analysis, we found the
> > following memory allocation path which consumes the memory with page_owner
> > enabled.
>
> I have a high lelel question.
> There is accounting of the socket memory for memcg that gets called from
> the networking layer. Did you check if the same call sites can be used
> for the system-wide accounting as well?

I also think about this. But we did not pass the `struct page` parameter to
the sock accounting memcg API. So we did not know the NUMA node
which allocated the socket buffer memory and cannot do node-level
statistics. In addition, there is another problem. If the user sends a 4096-byte
message, we only charge one page to the memcg but the system allocates 8
pages. So if we reuse the same call sites for the system-wide accounting,
the statistical count we get is always smaller than the actual situation.

>
> > 849698 times:
> > Page allocated via order 3, mask 0x4052c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP)
> > __alloc_pages_nodemask+0x11d/0x290
> > skb_page_frag_refill+0x68/0xf0
> > sk_page_frag_refill+0x19/0x70
> > tcp_sendmsg_locked+0x2f4/0xd10
> > tcp_sendmsg+0x29/0xa0
> > sock_sendmsg+0x30/0x40
> > sock_write_iter+0x8f/0x100
> > __vfs_write+0x10b/0x190
> > vfs_write+0xb0/0x190
> > ksys_write+0x5a/0xd0
> > do_syscall_64+0x5d/0x110
> > entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > ---
> > drivers/base/node.c | 2 ++
> > drivers/net/virtio_net.c | 3 +--
>
> Is virtio-net the only dirver that requred an update?

Yeah, only virtio-net needs an update. Because only it uses the
skb_page_frag_refill() API.

>
> > fs/proc/meminfo.c | 1 +
> > include/linux/mmzone.h | 1 +
> > include/linux/skbuff.h | 43 ++++++++++++++++++++++++++++++++++++++--
> > kernel/exit.c | 3 +--
> > mm/page_alloc.c | 7 +++++--
> > mm/vmstat.c | 1 +
> > net/core/sock.c | 8 ++++----
> > net/ipv4/tcp.c | 3 +--
> > net/xfrm/xfrm_state.c | 3 +--
> > 11 files changed, 59 insertions(+), 16 deletions(-)
> >

--
Yours,
Muchun