From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 40AF42405ED; Mon, 1 Dec 2025 06:10:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764569440; cv=none; b=AX4pk3+iVBThe3qqm++QjGulIA1gGZW/q9IeVyp6SQeMIdFyGwx97SmhfMe4uDbwVTbKXZjPP+XbITt/6NE/fU7dl/wHZTVbfivnE4CcFf6Ie4TGk+4PIPV1Z13t7pUS280WyOTVdHxkyJ+7xB2S2xRP4CeHaPo4/fE3Om372eI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764569440; c=relaxed/simple; bh=nD/uN2nQjuEcCbUGVV7Oea/rGh4tOwXodK7Pjls8eLM=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nS2pQSvDAMpDzZSBFi2PNoxotQxXG82UQIYUHGL2j186GQNGtF9gYHnisiB9wUv4No9JCLjkACXrg+hk682Fu5tk9fW/p+KdVYUtlaOmQJWbYQNzLU9ilRrIOPIsrzkNHZiRnDTMD9hlKlvAGW8egsxhiG0V547xYWztWm42dI8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=T/3M8oGa; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="T/3M8oGa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3DEFDC19421; Mon, 1 Dec 2025 06:10:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764569439; bh=nD/uN2nQjuEcCbUGVV7Oea/rGh4tOwXodK7Pjls8eLM=; h=From:To:Subject:Date:In-Reply-To:References:From; b=T/3M8oGaSBrcSqR7IBpoJ8LlXjGs1xBAXvu39bTQyYHoyAYdnV3OHPrEWdRfWBP5i xb6/6H6xJkTi+dO++y1wfJIrKwou8NgXObVF6Y8f/uass5rvLwhJyCCkjftEGDKySO eKO9SfYdafy/10geR2pR8WdskQ36cfYHKHzUU5vC3f+EWUUrrAWK7dx0U87mJgDUVe lPpaLBWMGt5YVE2Dbq0sltKyYHBnDMXA2SRL+9Fg2kpkGKcXPe3ql6INPXMDssct5W beeqkATNjuBkLnldeT8VPxB9xOXL0V7TLmwraYZb6YiAVYddQzOg6DHwNQXpN57MpW m7AYtRtFJZ3Rw== From: Allison Henderson To: netdev@vger.kernel.org, pabeni@redhat.com, edumazet@google.com, rds-devel@oss.oracle.com, kuba@kernel.org, horms@kernel.org, linux-rdma@vger.kernel.org, allison.henderson@oracle.com Subject: [PATCH net-next v3 2/2] net/rds: Give each connection path its own workqueue Date: Sun, 30 Nov 2025 23:10:36 -0700 Message-ID: <20251201061036.48865-3-achender@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251201061036.48865-1-achender@kernel.org> References: <20251201061036.48865-1-achender@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Allison Henderson RDS was written to require ordered workqueues for "cp->cp_wq": Work is executed in the order scheduled, one item at a time. If these workqueues are shared across connections, then work executed on behalf of one connection blocks work scheduled for a different and unrelated connection. Luckily we don't need to share these workqueues. While it obviously makes sense to limit the number of workers (processes) that ought to be allocated on a system, a workqueue that doesn't have a rescue worker attached, has a tiny footprint compared to the connection as a whole: A workqueue costs ~900 bytes, including the workqueue_struct, pool_workqueue, workqueue_attrs, wq_node_nr_active and the node_nr_active flex array. Each connection can have up to 8 (RDS_MPATH_WORKERS) paths for a worst case of ~7 KBytes per connection. While an RDS/IB connection totals only ~5 MBytes. So we're getting a signficant performance gain (90% of connections fail over under 3 seconds vs. 40%) for a less than 0.02% overhead. RDS doesn't even benefit from the additional rescue workers: of all the reasons that RDS blocks workers, allocation under memory pressue is the least of our concerns. And even if RDS was stalling due to the memory-reclaim process, the work executed by the rescue workers are highly unlikely to free up any memory. If anything, they might try to allocate even more. By giving each connection path its own workqueues, we allow RDS to better utilize the unbound workers that the system has available. Signed-off-by: Somasundaram Krishnasamy Signed-off-by: Allison Henderson --- net/rds/connection.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/net/rds/connection.c b/net/rds/connection.c index dc7323707f450..cfe6b50db8a6f 100644 --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -269,7 +269,11 @@ static struct rds_connection *__rds_conn_create(struct net *net, __rds_conn_path_init(conn, &conn->c_path[i], is_outgoing); conn->c_path[i].cp_index = i; - conn->c_path[i].cp_wq = rds_wq; + conn->c_path[i].cp_wq = + alloc_ordered_workqueue("krds_cp_wq#%lu/%d", 0, + rds_conn_count, i); + if (!conn->c_path[i].cp_wq) + conn->c_path[i].cp_wq = rds_wq; } rcu_read_lock(); if (rds_destroy_pending(conn)) @@ -471,6 +475,11 @@ static void rds_conn_path_destroy(struct rds_conn_path *cp) WARN_ON(work_pending(&cp->cp_down_w)); cp->cp_conn->c_trans->conn_free(cp->cp_transport_data); + + if (cp->cp_wq != rds_wq) { + destroy_workqueue(cp->cp_wq); + cp->cp_wq = NULL; + } } /* -- 2.43.0