From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753033AbcBATOG (ORCPT ); Mon, 1 Feb 2016 14:14:06 -0500 Received: from mail-bn1bon0069.outbound.protection.outlook.com ([157.56.111.69]:43168 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752749AbcBATOD (ORCPT ); Mon, 1 Feb 2016 14:14:03 -0500 X-Greylist: delayed 922 seconds by postgrey-1.27 at vger.kernel.org; Mon, 01 Feb 2016 14:14:02 EST Authentication-Results: spf=none (sender IP is 165.204.84.222) smtp.mailfrom=amd.com; arndb.de; dkim=none (message not signed) header.d=none;arndb.de; dmarc=permerror action=none header.from=amd.com; X-WSS-ID: 0O1VU1M-08-MFU-02 X-M-MSG: Subject: Re: [PATCH v2] ata: add AMD Seattle platform driver To: Arnd Bergmann References: <1452789071-4090-1-git-send-email-brijesh.singh@amd.com> <5730117.gx9ezcyLp7@wuerfel> <56A7A534.6040208@amd.com> <3904852.c3HykPsQQ2@wuerfel> CC: , Tejun Heo , , , From: Brijesh Singh Message-ID: <56AFAA46.6090403@amd.com> Date: Mon, 1 Feb 2016 12:56:06 -0600 User-Agent: Mozilla/5.0 (X11; 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You mentioned that you believe that calling > into the AML interpreter up to 100 times per second is a noticeable > overhead, but I doubt that and would like to see actual number backing > that up. Note that most of the time, the status of the LEDs won't even > change, so the driver does not have to call into the AML while I/O > is in progress, or while it is stopped, only for the transition or in > case of locate and fault events that should be extremely rare. > During disk activity ahci_sw_activity_blink() is called based on timer expiration (~100ms). I just enabled the function profiler for 'dd if=/dev/zero of=/root/tmp bs=1M count=4096' and see the output below. The function was called 37 times in 2.5s #echo 1 > function_profile_enabled #dd if=/dev/zero of=/root/tempfile bs=1M count=4096 4096+0 records in 4096+0 records out 4294967296 bytes (4.3 GB) copied, 2.57334 s, 1.7 GB/s #echo 0 > function_profile_enabled #cat trace_stat/* Function Hit Time Avg s^2 -------- --- ---- --- --- seattle_transmit_led_message 37 25.088 us 0.678 us 0.050 us I am not debating on your AML call recommendation, it sounds like a good idea however BIOS is already released hence its bit late to add AML methods for this. I am seeking guidance on what can be done in the given situation. I thought platform driver is one option to get this feature enabled in kernel. - Brijesh > Arnd >