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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3EE72C5AD7B for ; Mon, 10 Aug 2026 15:11:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=jmQRvX1k1SiKuSCh+skMmpVu8Z7eNcE8mftGlIJOuk8=; b=BiWXtp6mhz0Pvmp2dUGofQUk8n F55ryZa/FhYqTp/8X3Zr2kAmFsHQXbE6sdRglkd8EypAiTtSEj+3Gk72sDs0RtvG2Y6rjkqoy5W26 MLVNKWmpDfCFpD6W9v0WdchjHFjbXCheOZMnNHJMf27MAPZaRxGX5sisapoNUKUK7oV3/OuBktAbH rZ/PIo3zoQnSI/uxDhD6OVcCQs0RKStzJP9J+gmMVyWgfIB0Qu9rD5Uxvw3ogfQZPaV9FqNCdPq8g c9YxPZ3VZtjTS0mVsQQVZMuuaF6Jz9PEtO6XL9jobruLyOVdNFXCq2RIcaIipMmQLRbmBcHSIdbrE H79AaLGQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wtReU-0000000C9il-24Fh; Mon, 10 Aug 2026 15:10:58 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wtReS-0000000C9iO-1S5t for linux-arm-kernel@lists.infradead.org; Mon, 10 Aug 2026 15:10:56 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id A44BF60120; Mon, 10 Aug 2026 15:10:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4A5DF1F000E9; Mon, 10 Aug 2026 15:10:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786374655; bh=jmQRvX1k1SiKuSCh+skMmpVu8Z7eNcE8mftGlIJOuk8=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=jF8fta5j/+/mrM3hVm4vX69fI1bUZxljfWcwWwLlrbTYVwhzgYQLijGA8xol4fxrT ymOxLPxU0YM+Df7HzHy40vOpGPdhA2Y/+Uqrh3eDT+8ydsYYwFyvVaCPUj/58Nw6hc UrUqCb3juBU7LblPWvsqWlwTK7y1eApb69j/im0bYqVnTtHbXCJ/MHwm4aTWz4XHvA Jb+Pyq/9guNk7AV1Q4V+iXY1Scpmt8Sxu/I/+28Y7OfxNNurhcH+7iYAAod+s9++Lf L8LINXKHQre61zJW8Gi4haetO0sHYI40UNG2PWJViSF9UHnCrRbUeEU4/qhuF5vLc/ p9+4ZzsbZT38A== Date: Mon, 10 Aug 2026 16:10:48 +0100 From: Will Deacon To: Leo Yan Cc: Suzuki K Poulose , Peter Zijlstra , Mike Leach , James Clark , Anshuman Khandual , Mark Rutland , Tamas Petz , Tamas Zsoldos , Michiel van Tol , Dev Jain , David Hildenbrand , Yabin Cui , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: Re: [PATCH 2/2] perf: arm_spe: Prefer large AUX mappings Message-ID: References: <20260810-perf_aux_trace_large_granule-v1-0-03306c9339e3@arm.com> <20260810-perf_aux_trace_large_granule-v1-2-03306c9339e3@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260810-perf_aux_trace_large_granule-v1-2-03306c9339e3@arm.com> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Aug 10, 2026 at 03:44:42PM +0100, Leo Yan wrote: > Commit 18049c8cff9c ("perf/aux: Allocate non-contiguous AUX pages by > default") made the AUX allocator use order-0 pages by default unless a > PMU explicitly asks for contiguous allocations. But that commit specifically calls out SPE as benefitting from non-contiguous pages: "For instance, ARM SPE and TRBE operate with virtual pages, and Coresight ETR allocates a separate buffer. For these PMUs, allocating contiguous AUX pages unnecessarily exacerbates memory fragmentation. This fragmentation can prevent their use on long-running devices." so why doesn't passing PERF_PMU_CAP_AUX_PREFER_LARGE reintroduce the problems that 18049c8cff9c was trying to solve? Will