From mboxrd@z Thu Jan 1 00:00:00 1970 From: Henrik Rydberg Subject: Re: Lost events in older kernels Date: Sat, 22 May 2010 12:27:15 +0200 Message-ID: <4BF7B183.2050801@euromail.se> References: <4BF7825F.2030405@seas.upenn.edu> <20100522074249.GA25143@core.coreip.homeip.net> <4BF7A247.5090307@seas.upenn.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from ch-smtp02.sth.basefarm.net ([80.76.149.213]:38941 "EHLO ch-smtp02.sth.basefarm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753744Ab0EVKb2 (ORCPT ); Sat, 22 May 2010 06:31:28 -0400 In-Reply-To: <4BF7A247.5090307@seas.upenn.edu> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Rafi Rubin Cc: Dmitry Torokhov , linux-input , Jiri Kosina , Mika Kuoppala Rafi Rubin wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 05/22/10 03:42, Dmitry Torokhov wrote: >> On Sat, May 22, 2010 at 03:06:07AM -0400, Rafi Rubin wrote: >>> I'm playing with a project with a 2.6.29 kernel, and the userspace application >>> seems to miss some events. Is there a particular fix that improved the handling? >>> >>> Also tried catting the dev to a file while testing, and the dump also is missing >>> some events. >>> >> No "interesting" patches went into evdev for a few release now... >> >> Hm, could it be that event queue is overflowing before userspace gets a >> chance to empty it. What kind of event rate are we talking here? >> > > Quite possibly. It is a multitouch device and we know Henrik's been concerned > with the load for a while. > > So to put some numbers behind his fears: > > 146668 hid events processed > 24952 evdev events captured with a cat > 30 seconds (give or take). > > This is for a mix of different numbers of fingers, but continuous use for those > 30 seconds. And X was running and reading the dev node too. Others have experienced this too. Mika has a patch for this, increasing the (kernel) evdev buffer quite a bit, from 64 to 256. I believe the reason it is not sent upstream is because it increases the footprint by 3 Kb. Perhaps a dynamic solution could work here. Henrik