From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Warasin Subject: damn slow SDHC card Date: Mon, 11 Jul 2011 19:39:29 +0200 Message-ID: <4E1B3551.1040505@endian.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from cerbero2.endian.it ([80.190.199.139]:49265 "EHLO smtp1.endian.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758403Ab1GKSGH (ORCPT ); Mon, 11 Jul 2011 14:06:07 -0400 Received: from localhost (localhost.localdomain [127.0.0.1]) by solaria.endian.it (Postfix) with ESMTP id 52E9A599384 for ; Mon, 11 Jul 2011 19:39:40 +0200 (CEST) Received: from smtp1.endian.com ([127.0.0.1]) by localhost (solaria.endian.it [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id KhPRGxutMChI for ; Mon, 11 Jul 2011 19:39:30 +0200 (CEST) Received: from smtp.frangart.endian.com (unknown [192.168.201.129]) by solaria.endian.it (Postfix) with ESMTP id CBFD1599363 for ; Mon, 11 Jul 2011 19:39:30 +0200 (CEST) Received: from localhost (localhost.localhost [127.0.0.1]) by smtp.frangart.endian.com (Postfix) with ESMTP id 5D329116EC3 for ; Mon, 11 Jul 2011 19:39:30 +0200 (CEST) Received: from [10.7.5.53] (unknown [10.7.5.53]) by smtp.frangart.endian.com (Postfix) with ESMTP id 330A6116EB9 for ; Mon, 11 Jul 2011 19:39:30 +0200 (CEST) Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: linux-mmc@vger.kernel.org hi guys i have /var and swap on an SD card (sandisk class4 4GB) in an embedded network device, which turns out to be reeeeally slow. System under certain circumstances freezes and in top i see iowait at 90% and processes which touch sd card, like kswapd, kjournald and *mmc*d are all on io-wait (D) i found some help at linaro for sorting out if it is the SD card, which most probably is and try now to search a card which is fast enough but tried also to sort out if maybe it is the kernel, because something is fishy there. can you guys help me a little on that? the card is a high-speed card, but it is not running in highspeed mode: cat /sys/kernel/debug/mmc0/ios clock: 25000000 Hz vdd: 20 (3.2 ~ 3.3 V) bus mode: 2 (push-pull) chip select: 0 (don't care) power mode: 2 (on) bus width: 2 (4 bits) timing spec: 0 (legacy) i then forced the card setting to highspeed mode (by commenting out some returns in mmc_switch_hs() and found out that the card meets all requirements for highspeed, but card->sw_caps.hs_max_dtr is 0 is that value the maximum bus speed which the card can handle? i assume when it is 0 it means it is limited to legacy specifications, which is quite slow (?) or is it regardless for performance if a SDHC card runs in legacy mode? thank you in advance kind regards, peter -- :: e n d i a n :: open source - open minds :: peter warasin :: http://www.endian.com :: peter@endian.com