Re: [Libguestfs] [nbdkit PATCH 1/2] server: Add support for corking

Any time we reply to NBD_CMD_READ or NBD_CMD_BLOCK_STATUS, we end up calling conn->send() more than once. Now that we've disabled Nagle's algorithm, this implies that we try harder to send the small header immediately, rather than batching it with the rest of the payload, which causes more overhead in the amount of actual network traffic. For interfaces that support corking (gnutls, or Linux TCP sockets), we can give a hint that the separate send() calls should be batched into a single network packet where practical. This patch just wires up support; the next one will actually use it and provide performance measurements. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- server/internal.h | 3 +++ server/connections.c | 25 +++++++++++++++++++++++++ server/crypto.c | 19 +++++++++++++++++++ 3 files changed, 47 insertions(+) diff --git a/server/internal.h b/server/internal.h index 2ee5e23..cb34323 100644 --- a/server/internal.h +++ b/server/internal.h @@ -145,6 +145,8 @@ typedef int (*connection_recv_function) (struct connection *, typedef int (*connection_send_function) (struct connection *, const void *buf, size_t len) __attribute__((__nonnull__ (1, 2))); +typedef int (*connection_cork_function) (struct connection *, bool) + __attribute__((__nonnull__ (1))); typedef void (*connection_close_function) (struct connection *) __attribute__((__nonnull__ (1)));