From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755956AbcBIWVS (ORCPT ); Tue, 9 Feb 2016 17:21:18 -0500 Received: from mail-pa0-f50.google.com ([209.85.220.50]:32921 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755568AbcBIWVQ (ORCPT ); Tue, 9 Feb 2016 17:21:16 -0500 To: anton@enomsg.org, ccross@android.com, keescook@chromium.org, tony.luck@intel.com From: "Shi, Yang" Subject: Very low responsiveness for pstore ftrace Cc: LKML , linux-fsdevel@vger.kernel.org Message-ID: <56BA6658.2000906@linaro.org> Date: Tue, 9 Feb 2016 14:21:12 -0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi folks, I'm newbie to pstore. I just did a quick try for pstore ftrace. But, I experience very serious responsiveness problem. When running "echo 1 > /sys/kernel/debug/pstore/record_ftrace", it took a couple of minutes to return (here return means to get prompt back) on my arm64 machine (8 A57 cores). time command shows: # time echo 1 > /sys/kernel/debug/pstore/record_ftrace hrtimer: interrupt took 17532560 ns real 7m35.717s user 0m0.004s sys 2m25.244s I had a quick look at the code, it looks there is a long critical section with irq disabled. If with CONFIG_PSTORE_CONSOLE enabled, the machine even can't response interrupts. The pstore console code also need acquire the same lock with irq disabled. The low responsiveness sounds not reasonable to me. Any idea? Thanks, Yang