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, 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 D81F3C64E8A for ; Mon, 30 Nov 2020 17:35:36 +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 57DF12074A for ; Mon, 30 Nov 2020 17:35:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 57DF12074A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id BF6D06E7D7; Mon, 30 Nov 2020 17:35:34 +0000 (UTC) Received: from fireflyinternet.com (unknown [77.68.26.236]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0BF286E7D4; Mon, 30 Nov 2020 17:35:32 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from localhost (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP (TLS) id 23166016-1500050 for multiple; Mon, 30 Nov 2020 17:35:30 +0000 MIME-Version: 1.0 In-Reply-To: <9ccd22f4-875b-7ac8-253c-06aab009b3e4@intel.com> References: <20201127120718.454037-1-matthew.auld@intel.com> <20201127120718.454037-125-matthew.auld@intel.com> <160648535829.2925.3905288434672946602@build.alporthouse.com> <9ccd22f4-875b-7ac8-253c-06aab009b3e4@intel.com> Subject: Re: [Intel-gfx] [RFC PATCH 124/162] drm/i915/lmem: allocate HWSP in lmem From: Chris Wilson To: Matthew Auld , intel-gfx@lists.freedesktop.org Date: Mon, 30 Nov 2020 17:35:29 +0000 Message-ID: <160675772908.12351.6595786834675111791@build.alporthouse.com> User-Agent: alot/0.9 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Abdiel Janulgue , Michel Thierry , dri-devel@lists.freedesktop.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Quoting Matthew Auld (2020-11-30 17:17:16) > On 27/11/2020 13:55, Chris Wilson wrote: > > Quoting Matthew Auld (2020-11-27 12:06:40) > >> From: Michel Thierry > > > > Rationale goes here. > > > > Is this wise? HWSP is very frequently read by the CPU, and expected to > > be cached on the CPU. > > > > What do the performance profiles indicate? > > Do you have a recommendation for an existing selftest or IGT to help > measure this? > > Also are you suggesting moving this to system memory, or just using a > different mapping type, if it's placed in local memory? Or maybe try > both? Although I'm pretty sceptical about !wc for local memory. A lot of worries go out of the window if this can be in system memory and snooped. For measuring, I suspect there is a lot of chaff that needs to be removed before individual microbenchmarks like perf/request discern any difference; although that would be a starting point. We do a lot of completion checking during execlists interrupt processing, and there we (cpu profiles at least) are sensitive to uncached reads. We can trivially construct a benchmark that only shows the impact of the WC reads; but the point where I think we would first notice from userspace is client wakeup latency scaling: benchmarks/gem_latency, which was once a point of major concern. Nowadays, we can couple that with a second concern about inducing system latency from interrupt processing time. -Chris _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel