>From 6962c003785f48b859fedaabc77ebe0dfe85e993 Mon Sep 17 00:00:00 2001 From: Richard W.M. Jones Date: Fri, 1 Apr 2011 13:29:06 +0100 Subject: [PATCH 3/4] protocol: Sleep for 1ms before reading log messages. As explained in the comment: /* QEMU's console emulates a 16550A serial port. The real 16550A * device has a small FIFO buffer (16 bytes) which means here we see * lots of small reads of 1-16 bytes in length, usually single * bytes. Sleeping here for a very brief period groups reads * together (so we usually get a few lines of output at once) and * improves overall throughput, as well as making the event * interface a bit more sane for callers. With a virtio-serial * based console (not yet implemented) we may be able to remove * this. XXX */ --- src/proto.c | 9 ++++++++- 1 files changed, 8 insertions(+), 1 deletions(-) diff --git a/src/proto.c b/src/proto.c index 39f30ae..7cd1d31 100644 --- a/src/proto.c +++ b/src/proto.c @@ -251,8 +251,15 @@ read_log_message_or_eof (guestfs_h *g, int fd, int error_if_eof) /* QEMU's console emulates a 16550A serial port. The real 16550A * device has a small FIFO buffer (16 bytes) which means here we see * lots of small reads of 1-16 bytes in length, usually single - * bytes. + * bytes. Sleeping here for a very brief period groups reads + * together (so we usually get a few lines of output at once) and + * improves overall throughput, as well as making the event + * interface a bit more sane for callers. With a virtio-serial + * based console (not yet implemented) we may be able to remove + * this. XXX */ + usleep (1000); + n = read (fd, buf, sizeof buf); if (n == 0) { /* Hopefully this indicates the qemu child process has died. */ -- 1.7.4.1