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 962EB3546F1 for ; Wed, 29 Oct 2025 17:46:11 +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=1761759973; cv=none; b=H3Xyrtj6mHJJbMs/35VgWaYBzer035udH+6np8127tzLEVWDSqeK1oSXXWLcQBEk0w7zgyrbaaCzwa1/aS1MFsehJvB3Sigdm5+QFgGaLiN54TTGbw7xRkaPEQjRwRjn17/Yjf+agEbJAhHiHMOWmDqiCUJYXUQ/oJ8UOOyYjaI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761759973; c=relaxed/simple; bh=wXBxpM5Cpm0B2MGpppxOJWRLNhJo3u7lt2LKE0ZIJZU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=B8ovJM9K35KjcOXPJSYqgaQvKerAYN8XWjyeDkAIEF+pOvXtqd2TNJ68+ZMnnE0C1kOHjPZWIwfgemslb228s/ndOdkFSGLciqurspVcAJQUBhpws+pojPWNNT1TdpvbqTS3BNhFp7n4Vr2JiW1KSeE5y355zzAopRLhgI8qf2M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aIgaQFYq; 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="aIgaQFYq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E2510C4CEF7; Wed, 29 Oct 2025 17:46:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761759971; bh=wXBxpM5Cpm0B2MGpppxOJWRLNhJo3u7lt2LKE0ZIJZU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aIgaQFYq8l9GbfIRsLWsxEMlwsutW9jqzZ0I38FNz5EJd36fNQF36rmSquJ+3lpZc TCFEKt7AWs8XaQNrb8Y1CDCf9tjdgvgzrF/zQ0CS5FB+/m4mi+8wdDAvSVcHLcZ/Wr myJj5MliH4pkNmdjmplKays4/n09pZG3k0c85RQtMsyEbKtaDHoVAH1x1Gld/4H4JC V9uiiped0CpisyEegLeGJMwvjietY6jwd9jBkhWxR7GpFGDgPPwyrlhElumCEEXvDb veCsoAGBgHSmCXUKN9ut2STSf/F/940niosAxuOlnVusBwmJ9q5snx9aFpmBaPNaYY JdsBl0GL+fGug== From: Allison Henderson To: netdev@vger.kernel.org Cc: allison.henderson@oracle.com Subject: [PATCH net-next v1 2/2] net/rds: Give each connection its own workqueue Date: Wed, 29 Oct 2025 10:46:09 -0700 Message-ID: <20251029174609.33778-3-achender@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251029174609.33778-1-achender@kernel.org> References: <20251029174609.33778-1-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 ~800 bytes, while an RDS/IB connection totals ~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 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 | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/net/rds/connection.c b/net/rds/connection.c index dc7323707f450..ac555f02c045e 100644 --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -269,7 +269,14 @@ 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) { + while (--i >= 0) + destroy_workqueue(conn->c_path[i].cp_wq); + conn = ERR_PTR(-ENOMEM); + goto out; + } } rcu_read_lock(); if (rds_destroy_pending(conn)) @@ -471,6 +478,9 @@ 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); + + destroy_workqueue(cp->cp_wq); + cp->cp_wq = NULL; } /* -- 2.43.0