Attachment 18368 Details for Bug 15678 – patch from master for v4.20

[patch] patch from master for v4.20

3712.patch (text/plain), 2.87 KB, created by Guenther Deschner on 2024-07-08 14:39:53 UTC

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Creator: Guenther Deschner

Created: 2024-07-08 14:39:53 UTC

Size: 2.87 KB

patch

obsolete

>From 0416e605b8eb56af3c96f767f3deaad612770a07 Mon Sep 17 00:00:00 2001
>From: Xavi Hernandez <xhernandez@redhat.com>
>Date: Thu, 27 Jun 2024 15:41:19 +0200
>Subject: [PATCH] Fix starvation of pending writes in CTDB queues
>
>CTDB uses a queue to receive requests and send answers. It works
>asynchronously using the tevent framework. However there was an issue
>that gave priority to the receiving side so, when a request was
>processed and the answer posted to the queue, if another incoming
>request arrived, it was served before sending the previous answer.
>
>This scenario could repeat for long periods of time if the frequency of
>incoming requests was high enough.
>
>Eventually, a small time gap between incoming request gave a chance to
>process the pending output queue, sending many answers in a burst.
>
>This patch makes sure that both queues (input and output) are processed
>if the event contains the appropriate flag.
>
>BUG: https://bugzilla.samba.org/show_bug.cgi?id=15678
>RN: Fix unnecessary delays in CTDB while processing requests under high
>load.
>
>Signed-off-by: Xavi Hernandez <xhernandez@redhat.com>
>Reviewed-by: Volker Lendecke <vl@samba.org>
>Reviewed-by: Martin Schwenke <martin@meltin.net>
>
>Autobuild-User(master): Volker Lendecke <vl@samba.org>
>Autobuild-Date(master): Mon Jul  1 09:17:43 UTC 2024 on atb-devel-224
>
>(cherry picked from commit 60550fbe184a5cefa55a8f0bab508f70def7a684)
>---
> ctdb/common/ctdb_io.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
>diff --git a/ctdb/common/ctdb_io.c b/ctdb/common/ctdb_io.c
>index bf8bc73b77d..9ac9b84a7fb 100644
>--- a/ctdb/common/ctdb_io.c
>+++ b/ctdb/common/ctdb_io.c
>@@ -272,7 +272,7 @@ static void queue_dead(struct tevent_context *ev, struct tevent_immediate *im,
> /*
>   called when an incoming connection is writeable
> */
>-static void queue_io_write(struct ctdb_queue *queue)
>+static bool queue_io_write(struct ctdb_queue *queue)
> {
> 	while (queue->out_queue) {
> 		struct ctdb_queue_pkt *pkt = queue->out_queue;
>@@ -294,14 +294,14 @@ static void queue_io_write(struct ctdb_queue *queue)
> 			queue->fd = -1;
> 			tevent_schedule_immediate(queue->im, queue->ctdb->ev,
> 						  queue_dead, queue);
>-			return;
>+			return false;
> 		}
>-		if (n <= 0) return;
>+		if (n <= 0) return true;
> 		
> 		if (n != pkt->length) {
> 			pkt->length -= n;
> 			pkt->data += n;
>-			return;
>+			return true;
> 		}
> 
> 		DLIST_REMOVE(queue->out_queue, pkt);
>@@ -310,6 +310,8 @@ static void queue_io_write(struct ctdb_queue *queue)
> 	}
> 
> 	TEVENT_FD_NOT_WRITEABLE(queue->fde);
>+
>+	return true;
> }
> 
> /*
>@@ -320,10 +322,13 @@ static void queue_io_handler(struct tevent_context *ev, struct tevent_fd *fde,
> {
> 	struct ctdb_queue *queue = talloc_get_type(private_data, struct ctdb_queue);
> 
>+	if (flags & TEVENT_FD_WRITE) {
>+		if (!queue_io_write(queue)) {
>+			return;
>+		}
>+	}
> 	if (flags & TEVENT_FD_READ) {
> 		queue_io_read(queue);
>-	} else {
>-		queue_io_write(queue);
> 	}
> }
> 
>-- 
>GitLab
>

Flags:

gd: review+
vl: review+
martins: review+
gd: ci-passed+

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