ctdb: Adding memory pool for queue callback

[Swen Schillig]

On Fri, 2018-09-28 at 15:48 +1000, Martin Schwenke wrote:
> Hi Swen,
> 
> This is generally a good improvement.
> 
> I think the following part of the commit message probably needs to be
> updated:
> 
>   All received messages are processed synchronously per queue,
>   therefore, a larger memory pool is not requried.
> 
> There are definitely packets that are processed asynchronously.  Any
> of
> the control handling functions called by ctdb_control_dispatch() that
> have async_reply passed to them can talloc_steal() the control
> structure
> (i.e. the packet, because structs on the wire!).  Similarly for
> things
> like ctdb_reply_call().
> 
> However, even with some packets processed asynchronously I think that
> this should provide a useful reduction in malloc()s.
> 
> Can you please take a look at these code paths and, if convinced,
> update the commit message?
Agree. 
Patch description updated.

Cheers Swen

-------------- next part --------------
From 97bc3dc7f35a0fbd3401a18cd01dfcb2be1c6eef Mon Sep 17 00:00:00 2001
From: Swen Schillig <swen at vnet.ibm.com>
Date: Mon, 12 Mar 2018 17:56:21 +0100
Subject: [PATCH] ctdb: Adding memory pool for queue callback

The received packet is copied into a newly allocated memory chunk for further
processing by the assigned callback. Once this is done, the memory is free'd.
This is repeated for each received packet making the memory allocation / free
an expensive task. To optimize this process, a memory pool is defined which
is sized identically to the queue's buffer.
During tests it could be seen that more than 95% of all messages were sized
below the standard buffer_size of 1k.

Signed-off-by: Swen Schillig <swen at vnet.ibm.com>
---
 ctdb/common/ctdb_io.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/ctdb/common/ctdb_io.c b/ctdb/common/ctdb_io.c
index 5bed7a61b31..073992fbce1 100644
--- a/ctdb/common/ctdb_io.c
+++ b/ctdb/common/ctdb_io.c
@@ -65,6 +65,7 @@ struct ctdb_queue {
 	size_t alignment;
 	void *private_data;
 	ctdb_queue_cb_fn_t callback;
+	char *data_pool;
 	const char *name;
 	uint32_t buffer_size;
 };
@@ -115,7 +116,7 @@ static void queue_process(struct ctdb_queue *queue)
 	}
 
 	/* Extract complete packet */
-	data = talloc_memdup(queue,
+	data = talloc_memdup(queue->data_pool,
 			     queue->buffer.data + queue->buffer.offset,
 			     pkt_size);
 
@@ -479,5 +480,11 @@ struct ctdb_queue *ctdb_queue_setup(struct ctdb_context *ctdb,
 		queue->buffer_size = 1024;
 	}
 
+	queue->data_pool = talloc_pool(queue, queue->buffer_size);
+	if (queue->data_pool == NULL) {
+		TALLOC_FREE(queue);
+		return NULL;
+	}
+
 	return queue;
 }
-- 
2.17.1