From 3a6379aa77c76030aa4d6d88943cd263950db508 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Tue, 10 Mar 2026 14:24:59 +0100 Subject: [PATCH] upload-pack: prefer flushing data over sending keepalive When using the sideband in git-upload-pack(1) we know to send out keepalive packets in case generating the pack takes too long. These keepalives take the form of a simple empty pktline. In the preceding commit we have adapted git-upload-pack(1) to buffer data more aggressively before sending it to the client. This creates an obvious optimization opportunity: when we hit the keepalive timeout while we still hold on to some buffered data, then it makes more sense to flush out the data instead of sending the empty keepalive packet. This is overall not going to be a significant win. Most keepalives will come before the pack data starts, and once pack-objects starts producing data, it tends to do so pretty consistently. And of course we can't send data before we see the PACK header, because the whole point is to buffer the early bit waiting for packfile URIs. But the optimization is easy enough to realize. Do so and flush out data instead of sending an empty pktline. While at it, drop the useless Suggested-by: Jeff King Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- upload-pack.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/upload-pack.c b/upload-pack.c index 04521e57c9..ef8f8189c1 100644 --- a/upload-pack.c +++ b/upload-pack.c @@ -466,18 +466,27 @@ static void create_pack_file(struct upload_pack_data *pack_data, } /* - * We hit the keepalive timeout without saying anything; send - * an empty message on the data sideband just to let the other - * side know we're still working on it, but don't have any data - * yet. + * We hit the keepalive timeout without saying anything. If we + * have pending data we flush it out to the caller now. + * Otherwise, we send an empty message on the data sideband + * just to let the other side know we're still working on it, + * but don't have any data yet. * * If we don't have a sideband channel, there's no room in the * protocol to say anything, so those clients are just out of * luck. */ if (!ret && pack_data->use_sideband) { - static const char buf[] = "0005\1"; - write_or_die(1, buf, 5); + if (output_state->packfile_started && output_state->used > 1) { + send_client_data(1, output_state->buffer, output_state->used - 1, + pack_data->use_sideband); + output_state->buffer[0] = output_state->buffer[output_state->used - 1]; + output_state->used = 1; + } else { + static const char buf[] = "0005\1"; + write_or_die(1, buf, 5); + } + last_sent_ms = now_ms; } }