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Re: [Qemu-devel] [PATCH 1/2] ISCSI: redo how we set up the events to onl
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 1/2] ISCSI: redo how we set up the events to only call qemu_aio_set_fd_handler() and qemu_notify_event() if something has changed. |
Date: |
Fri, 25 May 2012 11:59:34 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 |
Il 25/05/2012 09:43, Ronnie Sahlberg ha scritto:
> Also first call out to the socket write functions director, and only set up
> the write event if the socket is full.
>
> This means that we will only need to invoke these two functions very rarely
> which will improve performance.
>
> Signed-off-by: Ronnie Sahlberg <address@hidden>
> ---
> block/iscsi.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++----------
> 1 files changed, 46 insertions(+), 10 deletions(-)
>
> diff --git a/block/iscsi.c b/block/iscsi.c
> index ed1ad7b..9642ee6 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -40,6 +40,8 @@ typedef struct IscsiLun {
> int lun;
> int block_size;
> unsigned long num_blocks;
> + IOHandler *read_handler;
> + IOHandler *write_handler;
> } IscsiLun;
>
> typedef struct IscsiAIOCB {
> @@ -105,18 +107,50 @@ static void
> iscsi_set_events(IscsiLun *iscsilun)
> {
> struct iscsi_context *iscsi = iscsilun->iscsi;
> + int need_set_fd = 0;
> + int need_notify_event = 0;
>
> - 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);
> -
> - /* If we just added the event for writeable we must call
> - and the socket is already writeable the callback might
> - not be invoked until after a short delay unless we call
> - qemu_notify_event().
> + /* Try to write as much as we can to the socket
> + * without setting up an event
> */
> - qemu_notify_event();
> + if (iscsi_which_events(iscsi) & POLLOUT) {
> + iscsi_process_write(iscsilun);
> + }
> +
> + if (iscsilun->read_handler == NULL) {
> + iscsilun->read_handler = iscsi_process_read;
> + need_set_fd = 1;
> + need_notify_event = 1;
> + }
This is not needed, just pass iscsi_process_read unconditionally to
qemu_aio_set_fd_handler.
> + if (iscsi_which_events(iscsi) & POLLOUT) {
> + if (iscsilun->write_handler == NULL) {
> + iscsilun->write_handler = iscsi_process_write;
> + need_set_fd = 1;
> + need_notify_event = 1;
> + }
> + } else {
> + if (iscsilun->write_handler != NULL) {
> + iscsilun->write_handler = NULL;
> + need_set_fd = 1;
> + }
> + }
> +
> + if (need_set_fd) {
> + qemu_aio_set_fd_handler(iscsi_get_fd(iscsi),
> + iscsilun->read_handler,
> + iscsilun->write_handler,
> + iscsi_process_flush,
> + iscsilun);
> +
> + /* If we just added an event that may trigger almost immediately
> + the callback might not be invoked until after a short
> + delay unless we call qemu_notify_event().
> + */
> + if (need_notify_event) {
> + qemu_notify_event();
> + }
> + }
What about this:
/* 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;
?
Paolo