From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760769AbZKZQMO (ORCPT ); Thu, 26 Nov 2009 11:12:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760677AbZKZQML (ORCPT ); Thu, 26 Nov 2009 11:12:11 -0500 Received: from mail-ew0-f219.google.com ([209.85.219.219]:52888 "EHLO mail-ew0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758984AbZKZQMJ (ORCPT ); Thu, 26 Nov 2009 11:12:09 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:subject:date:user-agent:mime-version:message-id:cc :content-type:content-transfer-encoding; b=rhqBkq9cPlsUUqsI4pN/g+tWync4qfaTs0RjHfkbGyzMkRoCK/XcfUefxZHirwb4DF dSNWBm8KqAga88P9JHkXCOhvV+6riYs2m5d0F7wDegcieqiIeyXhbA+gdZw4ScLMUx7v ddSrffvM75nMFPtfcbOGmxpFx9dQC8155wLuM= From: Bartlomiej Zolnierkiewicz To: Jeff Garzik Subject: [PATCH] libata: add comment documenting PIO latency issues on UP Date: Thu, 26 Nov 2009 17:11:16 +0100 User-Agent: KMail/1.12.2 (Linux/2.6.31.5-0.1-desktop; KDE/4.3.1; x86_64; ; ) MIME-Version: 1.0 Message-Id: <200911261711.16954.bzolnier@gmail.com> Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Based on: http://lkml.indiana.edu/hypermail/linux/kernel/0908.2/01420.html Signed-off-by: Bartlomiej Zolnierkiewicz --- drivers/ata/libata-core.c | 7 +++++++ 1 file changed, 7 insertions(+) Index: b/drivers/ata/libata-core.c =================================================================== --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -6624,6 +6624,13 @@ static int __init ata_init(void) { ata_parse_force_param(); + /* + * FIXME: In UP case, there is only one workqueue thread and if you + * have more than one PIO device, latency is bloody awful, with + * occasional multi-second "hiccups" as one PIO device waits for + * another. It's an ugly wart that users DO occasionally complain + * about; luckily most users have at most one PIO polled device. + */ ata_wq = create_workqueue("ata"); if (!ata_wq) goto free_force_tbl;