On Mon, Oct 12, 2020 at 6:22 AM Muchun Song [off-list ref] wrote:

On Mon, Oct 12, 2020 at 2:39 AM Cong Wang [off-list ref] wrote:

quoted

On Sat, Oct 10, 2020 at 3:39 AM Muchun Song [off-list ref] wrote:

quoted

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
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.

quoted

quoted

 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().
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.

Pages can be transferred from pipe to socket, socket to pipe (splice()
and zerocopy friends...)

 If you want to track TCP memory allocations, you always can look at
/proc/net/sockstat,
without adding yet another expensive memory accounting.