On 04/26/2018 02:16 PM, Andy Lutomirski wrote:

At the risk of further muddying the waters, there's another minor tweak
that could improve performance on certain workloads.  Currently you mmap()
a range for a given socket and then getsockopt() to receive.  If you made
it so you could mmap() something once for any number of sockets (by
mmapping /dev/misc/tcp_zero_receive or whatever), then the performance of
the getsockopt() bit would be identical, but you could release the mapping
for many sockets at once with only a single flush.  For some use cases,
this could be a big win.

You could also add this later easily enough, too.

I believe I implemented what you just described.

The getsockopt() call checks that the VMA was created by a mmap() to one TCP socket.

It does not check that the vma was created by mmap() on the same socket,
because we do not need this extra check really.

So you presumably could use mmap() to grab 1GB of virtual space, then split it
as you wish for different sockets.

Thanks.