From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC665C3F2D1 for ; Thu, 5 Mar 2020 05:56:31 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CBD00208CD for ; Thu, 5 Mar 2020 05:56:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CBD00208CD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 5B3CF6E04E; Thu, 5 Mar 2020 05:56:31 +0000 (UTC) Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by gabe.freedesktop.org (Postfix) with ESMTPS id 96FD66E04E for ; Thu, 5 Mar 2020 05:56:29 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Mar 2020 21:56:28 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,516,1574150400"; d="scan'208";a="240698728" Received: from adixit-mobl.amr.corp.intel.com (HELO adixit-arch.intel.com) ([10.252.139.179]) by orsmga003.jf.intel.com with ESMTP; 04 Mar 2020 21:56:28 -0800 Date: Wed, 04 Mar 2020 21:56:28 -0800 Message-ID: <87o8tb2vlf.wl-ashutosh.dixit@intel.com> From: "Dixit, Ashutosh" To: Lionel Landwerlin In-Reply-To: References: <20200303221905.25866-1-umesh.nerlige.ramappa@intel.com> <20200303221905.25866-8-umesh.nerlige.ramappa@intel.com> <87v9nku0uu.wl-ashutosh.dixit@intel.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?ISO-8859-4?Q?Goj=F2?=) APEL/10.8 EasyPG/1.0.0 Emacs/26 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Subject: Re: [Intel-gfx] [PATCH 7/7] drm/i915/perf: add flushing ioctl X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Wed, 04 Mar 2020 00:52:34 -0800, Lionel Landwerlin wrote: > > On 04/03/2020 07:48, Dixit, Ashutosh wrote: > > On Tue, 03 Mar 2020 14:19:05 -0800, Umesh Nerlige Ramappa wrote: > >> From: Lionel Landwerlin > >> > >> With the currently available parameters for the i915-perf stream, > >> there are still situations that are not well covered : > >> > >> If an application opens the stream with polling disable or at very low > >> frequency and OA interrupt enabled, no data will be available even > >> though somewhere between nothing and half of the OA buffer worth of > >> data might have landed in memory. > >> > >> To solve this issue we have a new flush ioctl on the perf stream that > >> forces the i915-perf driver to look at the state of the buffer when > >> called and makes any data available through both poll() & read() type > >> syscalls. > >> > >> v2: Version the ioctl (Joonas) > >> v3: Rebase (Umesh) > >> > >> Signed-off-by: Lionel Landwerlin > >> Signed-off-by: Umesh Nerlige Ramappa > > [snip] > > > >> +/** > >> + * i915_perf_flush_data - handle `I915_PERF_IOCTL_FLUSH_DATA` ioctl > >> + * @stream: An enabled i915 perf stream > >> + * > >> + * The intention is to flush all the data available for reading from the OA > >> + * buffer > >> + */ > >> +static void i915_perf_flush_data(struct i915_perf_stream *stream) > >> +{ > >> + stream->pollin = oa_buffer_check(stream, true); > >> +} > > Since this function doesn't actually wake up any thread (which anyway can > > be done by sending a signal to the blocked thread), is the only purpose of > > this function to update OA buffer head/tail? But in that it is not clear > > why a separate ioctl should be created for this, can't the read() call > > itself call oa_buffer_check() to update the OA buffer head/tail? > > > > Again just trying to minimize uapi changes if possible. > > Most applications will call read() after being notified by poll()/select() > that some data is available. Correct this is the standard non blocking read behavior. > Changing that behavior will break some of the existing perf tests . I am not suggesting changing that (that standard non blocking read behavior). > If any data is available, this new ioctl will wake up existing waiters on > poll()/select(). The issue is we are not calling wake_up() in the above function to wake up any blocked waiters. The ioctl will just update the OA buffer head/tail so that (a) a subsequent blocking read will not block, or (b) a subsequent non blocking read will return valid data (not -EAGAIN), or (c) a poll/select will not block but return immediately saying data is available. That is why it seems to me the ioctl is not required, updating the OA buffer head/tail can be done as part of the read() (and the poll/select) calls themselves. We will investigate if this can be done and update the patches in the next revision accordingly. Thanks! _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx