Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753919Ab1BVHno (ORCPT ); Tue, 22 Feb 2011 02:43:44 -0500 Received: from mail-bw0-f51.google.com ([209.85.214.51]:58205 "EHLO mail-bw0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753795Ab1BVHnn (ORCPT ); Tue, 22 Feb 2011 02:43:43 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; b=aaZNrQvX27VIe00Hkyl7uHRMr2Soe7By1f/C9MEgiSeuIAolQzM6Fqp8laY/7mfRbI ihqh1hXSkgJZKO7orKK3Bv/AkBEjKtct5ToeQQnluGamkcZi943YXA2fmHOvBlsxwviC EfTrhALbGu1MD8LnqnRPOecp9H4GThltcNNmQ= Message-ID: <4D6367B3.9050306@googlemail.com> Date: Tue, 22 Feb 2011 08:37:23 +0100 From: Clemens Ladisch User-Agent: Thunderbird 2.0.0.24 (Windows/20100228) MIME-Version: 1.0 To: Arthur Marsh CC: Andrea Arcangeli , alsa-user@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [Alsa-user] new source of MIDI playback slow-down identified - 5a03b051ed87e72b959f32a86054e1142ac4cf55 thp: use compaction in kswapd for GFP_ATOMIC order > 0 References: In-Reply-To: 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 Content-Length: 1679 Lines: 42 Arthur Marsh wrote: > I'm experiencing MIDI playback slow-downs when I'm observing kswapd0 > active (a few percent of cpu in top output) in recent kernels. > > I git-bisected the problem down to: > > commit 5a03b051ed87e72b959f32a86054e1142ac4cf55 > Author: Andrea Arcangeli > Date: Thu Jan 13 15:47:11 2011 -0800 > > thp: use compaction in kswapd for GFP_ATOMIC order > 0 > > This takes advantage of memory compaction to properly generate pages of > order > 0 if regular page reclaim fails and priority level becomes more > severe and we don't reach the proper watermarks. > > Signed-off-by: Andrea Arcangeli > Signed-off-by: Andrew Morton > Signed-off-by: Linus Torvalds > > I ran git-bisect over the weekend, building and installing ALSA 1.0.24 > with each kernel. After identifying the above commit, I rebuilt the 2.6 > head with that commit reverted and verified that the problem was no > longer present. Apparently, huge page compaction disables interrupts for much too long. > MIDI playback was via aplaymidi -p 17:0 to a Soundblaster Audigy 2 ZS > (SB0350) wavetable. The ALSA sequencer uses either the system timer or an HR timer at 1 kHz to deliver MIDI commands (notes); the wavetable driver requires its own interrupts in regular 5.3 ms intervals. Regards, Clemens -- 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/