From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 19 Nov 2002 18:10:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 19 Nov 2002 18:10:34 -0500 Received: from svr-ganmtc-appserv-mgmt.ncf.coxexpress.com ([24.136.46.5]:13838 "EHLO svr-ganmtc-appserv-mgmt.ncf.coxexpress.com") by vger.kernel.org with ESMTP id ; Tue, 19 Nov 2002 18:10:32 -0500 Subject: Re: [patch] remove magic numbers in block queue initialization From: Robert Love To: akpm@digeo.com Cc: linux-kernel@vger.kernel.org, joe@perches.com In-Reply-To: <1037747198.1252.2259.camel@phantasy> References: <1037747198.1252.2259.camel@phantasy> Content-Type: text/plain Organization: Message-Id: <1037747861.1253.2273.camel@phantasy> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.0 Date: 19 Nov 2002 18:17:41 -0500 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Joe Perches just pointed out we can make the second `if' an `else if'. Probably does not affect the object code, but since we are editing this here now, why not... Updated patch applied. Robert Love Replace magic numbers in block queue init with sexy defines. Also change an if to an else if in the name of micro-ops. drivers/block/ll_rw_blk.c | 32 ++++++++++++++++++++++++-------- 1 files changed, 24 insertions(+), 8 deletions(-) diff -urN linux-2.5.48/drivers/block/ll_rw_blk.c linux/drivers/block/ll_rw_blk.c --- linux-2.5.48/drivers/block/ll_rw_blk.c 2002-11-17 23:29:22.000000000 -0500 +++ linux/drivers/block/ll_rw_blk.c 2002-11-19 17:59:07.000000000 -0500 @@ -2109,6 +2109,22 @@ __blk_put_request(req->q, req); } +/* + * The maximum and minimum free requests slots in the queue are + * dynamically calculated as a function of total memory. Below is the + * upper and lower bound to those calculations. We do not want the + * queue too large, as more memory than desired can be under writeback. + */ +#define MAX_QUEUE_REQUESTS 128 +#define MIN_QUEUE_REQUESTS 16 + +/* + * Number of requests to batch together is calculated as the queue size + * over BATCH_QUEUE_FACTOR. This number is capped at MAX_BATCH_REQUESTS + */ +#define BATCH_QUEUE_FACTOR 8 +#define MAX_BATCH_REQUESTS 8 + int __init blk_dev_init(void) { int total_ram = nr_free_pages() << (PAGE_SHIFT - 10); @@ -2125,14 +2141,14 @@ * We use this many requests for reads, and this many for writes. */ queue_nr_requests = (total_ram >> 9) & ~7; - if (queue_nr_requests < 16) - queue_nr_requests = 16; - if (queue_nr_requests > 128) - queue_nr_requests = 128; - - batch_requests = queue_nr_requests / 8; - if (batch_requests > 8) - batch_requests = 8; + if (queue_nr_requests < MIN_QUEUE_REQUESTS) + queue_nr_requests = MIN_QUEUE_REQUESTS; + else if (queue_nr_requests > MAX_QUEUE_REQUESTS) + queue_nr_requests = MAX_QUEUE_REQUESTS; + + batch_requests = queue_nr_requests / BATCH_QUEUE_FACTOR; + if (batch_requests > MAX_BATCH_REQUESTS) + batch_requests = MAX_BATCH_REQUESTS; printk("block request queues:\n"); printk(" %d requests per read queue\n", queue_nr_requests);