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=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 B6B42C433DF for ; Mon, 17 Aug 2020 09:03:22 +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 83B84206C0 for ; Mon, 17 Aug 2020 09:03:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 83B84206C0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.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 EC9F66E06D; Mon, 17 Aug 2020 09:03:21 +0000 (UTC) Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by gabe.freedesktop.org (Postfix) with ESMTPS id 74B7D6E06D for ; Mon, 17 Aug 2020 09:03:20 +0000 (UTC) IronPort-SDR: OSv6dnIkwJvIBcfZuYF0fPxGxgiT9eqZUCOHLw0LWTkAxGYKT1lj/oPxLUfiAuEGaUMoFcC+zO SfNHrNJRc4RA== X-IronPort-AV: E=McAfee;i="6000,8403,9715"; a="218987727" X-IronPort-AV: E=Sophos;i="5.76,322,1592895600"; d="scan'208";a="218987727" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Aug 2020 02:03:19 -0700 IronPort-SDR: ZYntDGJH8Ot6aKf8h/3tNyMtwWFJTOdKnCAvAqYXnWcka96y5S2DNNXzpgzz70HV1kwBhtlSJM WHRN3VTkw+dw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,322,1592895600"; d="scan'208";a="400135478" Received: from gaia.fi.intel.com ([10.237.72.192]) by fmsmga001.fm.intel.com with ESMTP; 17 Aug 2020 02:03:18 -0700 Received: by gaia.fi.intel.com (Postfix, from userid 1000) id 498285C2770; Mon, 17 Aug 2020 12:02:31 +0300 (EEST) From: Mika Kuoppala To: Chris Wilson , intel-gfx@lists.freedesktop.org In-Reply-To: <159743629912.31882.4041606652398941372@build.alporthouse.com> References: <20200814155735.29138-1-chris@chris-wilson.co.uk> <20200814155735.29138-3-chris@chris-wilson.co.uk> <87ft8p135h.fsf@gaia.fi.intel.com> <159743409290.31882.4297809836771338545@build.alporthouse.com> <159743629912.31882.4041606652398941372@build.alporthouse.com> Date: Mon, 17 Aug 2020 12:02:31 +0300 Message-ID: <87d03p1w7s.fsf@gaia.fi.intel.com> MIME-Version: 1.0 Subject: Re: [Intel-gfx] [PATCH 3/3] drm/i915/gt: Apply the CSB w/a for all 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Chris Wilson writes: > Quoting Chris Wilson (2020-08-14 20:41:32) >> Quoting Mika Kuoppala (2020-08-14 19:41:14) >> > Chris Wilson writes: >> > > - entry = READ_ONCE(*csb); >> > > - if (unlikely(entry == -1)) { >> > > - preempt_disable(); >> > > - if (wait_for_atomic_us((entry = READ_ONCE(*csb)) != -1, 50)) >> > >> > If we get this deep into desperation, should we start to apply more >> > pressure. Ie, rmb instead of just instructing the compiler. And could also >> > start to invalidate the entry which obviously if of no use. >> >> I had a rmb() here; removing it did not appear to make any difference >> whatsoever to the average delay. The extreme case would be a full >> mb(); clflush(); mb() read. I haven't timed the average for that.... > > +static inline u64 __csb_read(u64 *csb) > +{ > + mb(); > + clflush(csb); > + mb(); > + > + return READ_ONCE(*csb); > +} > > [ 1554.274204] csb: 1793 misses, avg 475ns, max 14727ns > > So no better on average or at worst. Well thanks for trying it out. We can attach it to hsdes as a note that there is not much to be done on cpu side :O -Mika > -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx