From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from plane.gmane.org ([80.91.229.3]:53014 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752833Ab2DWRH5 (ORCPT ); Mon, 23 Apr 2012 13:07:57 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1SMMjz-0005KJ-R2 for linux-media@vger.kernel.org; Mon, 23 Apr 2012 19:07:55 +0200 Received: from d67-193-214-242.home3.cgocable.net ([67.193.214.242]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 23 Apr 2012 19:07:55 +0200 Received: from brian by d67-193-214-242.home3.cgocable.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 23 Apr 2012 19:07:55 +0200 To: linux-media@vger.kernel.org From: "Brian J. Murrell" Subject: Re: HVR-1600: Skipped encoder MPEG, MDL 63, 62 times - it must have dropped out of rotation Date: Mon, 23 Apr 2012 13:07:45 -0400 Message-ID: References: <1335128213.2602.23.camel@palomino.walls.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig8F1A40EB0AB272E549A0AC78" In-Reply-To: <1335128213.2602.23.camel@palomino.walls.org> Sender: linux-media-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig8F1A40EB0AB272E549A0AC78 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 12-04-22 04:56 PM, Andy Walls wrote: >=20 > If, in your system, IRQ service for device A under some circumstances > has precendence over IRQ service for the CX23418 and hence holds off it= s > service; and the irq handler in the driver for device A decides to > perform some some long I/O operations with device A; then it doesn't > matter how fast your CPU is.=20 Yes, quite true. I was forgetting about how nasty an irq handler can be on other hardware. > You may wish to use perf or ftrace, or some other tool/method of > measuring kernel interrupt handling latency to find out what causes any= > delays from the CX23418 raising its IRQ line to cx18_irq_handler() bein= g > called by the kernel. Excellent idea. I'm afraid I'm quite (read: very) green in the area of kernel performance profiling. But I'm smart. Looking around, it seems that with ftrace, I am looking for the irqsoff tracer, is that correct? Unfortunately my kernel doesn't have that one: # cat /sys/kernel/debug/tracing/available_tracers blk function_graph mmiotrace wakeup_rt wakeup function nop I can't seem to find any useful information on using perf to analyze ISR latency. Any pointers? Cheers, b. --------------enig8F1A40EB0AB272E549A0AC78 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk+VjGEACgkQl3EQlGLyuXCoAACgiDbGkuvGQaO+jMUEemK04Y5o fysAn2iR+HucWKxOratz8RdDsvHX4oln =tmyo -----END PGP SIGNATURE----- --------------enig8F1A40EB0AB272E549A0AC78--