Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932488AbVJDO0Y (ORCPT ); Tue, 4 Oct 2005 10:26:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932494AbVJDO0Y (ORCPT ); Tue, 4 Oct 2005 10:26:24 -0400 Received: from mx1.cdacindia.com ([203.199.132.35]:26040 "HELO mailx.cdac.ernet.in") by vger.kernel.org with SMTP id S932488AbVJDO0X (ORCPT ); Tue, 4 Oct 2005 10:26:23 -0400 Message-ID: <434288E9.3090108@cdac.in> Date: Tue, 04 Oct 2005 19:21:37 +0530 From: Karthik Sarangan User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040805 Netscape/7.2 X-Accept-Language: en-us, en MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Subject: Using DMA in read/write, setting block size for I/O Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 815 Lines: 29 In my application, I have the following code. int main(void) { char *pcBuffer; posix_memalign((void **) pcBuffer, 512, 262144); int ifd = open("/dev/sdb", O_DIRECT | O_RDWR); long lLen; lLen = read(ifd, pcBuffer, 262144); close(ifd); return 0; } Will the underlying block device read a single 256KB block from the hdd into pcBuffer or will it read 256KB as a set of smaller blocks? Since the buffer is memory aligned will it enable DMA? scsi disk driver is adaptec aic79xx.o distro is RedHat Enterprise Linux WS 4 (kernel-2.6.9-11) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/