From c9b9f6824fd82058f6918b64d8fd9b1578fac353 Mon Sep 17 00:00:00 2001 From: Ronnie Sahlberg Date: Tue, 22 May 2012 19:56:36 +1000 Subject: [PATCH] ISCSI: redo how we set up the events Call qemu_notify_event() after updating events. Otherwise, If we add an event for -is-writeable but the socket is already writeable there may be a delay before the event callback is actually triggered. Those delays would in particular hurt performance during BIOS boot and when the GRUB bootloader reads the kernel and initrd. But first call out to the socket write functions directly, and only set up the write event if the socket is full. This will happen very rarely and this improves performance. Signed-off-by: Ronnie Sahlberg --- block/iscsi.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/block/iscsi.c b/block/iscsi.c index d37c4ee171..db41bb7582 100644 --- a/block/iscsi.c +++ b/block/iscsi.c @@ -39,6 +39,7 @@ typedef struct IscsiLun { int lun; int block_size; unsigned long num_blocks; + int events; } IscsiLun; typedef struct IscsiAIOCB { @@ -104,11 +105,27 @@ static void iscsi_set_events(IscsiLun *iscsilun) { struct iscsi_context *iscsi = iscsilun->iscsi; + int ev; - qemu_aio_set_fd_handler(iscsi_get_fd(iscsi), iscsi_process_read, - (iscsi_which_events(iscsi) & POLLOUT) - ? iscsi_process_write : NULL, - iscsi_process_flush, iscsilun); + /* We always register a read handler. */ + ev = POLLIN; + ev |= iscsi_which_events(iscsi); + if (ev != iscsilun->events) { + qemu_aio_set_fd_handler(iscsi_get_fd(iscsi), + iscsi_process_read, + (ev & POLLOUT) ? iscsi_process_write : NULL, + iscsi_process_flush, + iscsilun); + + } + + /* If we just added an event, the callback might be delayed + * unless we call qemu_notify_event(). + */ + if (ev & ~iscsilun->events) { + qemu_notify_event(); + } + iscsilun->events = ev; } static void