From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0405D1DFCB for ; Sun, 29 Jun 2025 23:05:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751238351; cv=none; b=oFbjSNp2aR6jtJwHiLIAgJLJnFbJgQuNLbYnQ6VF2GbIKu5NGHYgdQZSIv4rUcdhYJvade7h27DafeqOYMQyfO0FKt4+acwPt97PHArOoC5cM2j0rq+9g28RWJQYK8Isu9PwP2b3uKYoTbuQRKPBWyhZwZBs78ipb4pTGypAS7o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751238351; c=relaxed/simple; bh=W82owXpwGpTGovuRtiMl4ETQSnevrtiA8edoKdquAuc=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=UBYCui+Duk3AdxS6JXUus0fv+MJvpOHEwrvnnrxWiNQxV8ynymIpQtbAM+VWkryv/rIOFVJbAe4hBqAsNyf5GGLN5fveGfHTmCgp+YuayiASpKuvkstDzorciLVEfL3KbFi26ZElgY2jM8riZdFXtwG2HxkCLArrqWT5nNByVD0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=tF6VIh2N; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="tF6VIh2N" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92564C4CEEB; Sun, 29 Jun 2025 23:05:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1751238350; bh=W82owXpwGpTGovuRtiMl4ETQSnevrtiA8edoKdquAuc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=tF6VIh2NGztTz8j/GldWe58g5f5QqvEyYmFNuGIA72367L4gYrgGcHFfR5sGvT1NN jcOJ7lRGh4r+rmQ5QhfztpZqqdv5uOnaI+jq1hjgCXRmZClbK2H96DHL3hvyD+7g8O 8xcy4nIKS0qqfTGgGd3shk0pT49MogJn4ynP4DOI= Date: Sun, 29 Jun 2025 16:05:49 -0700 From: Andrew Morton To: Dev Jain Cc: ryan.roberts@arm.com, david@redhat.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, anshuman.khandual@arm.com, peterx@redhat.com, joey.gouly@arm.com, ioworker0@gmail.com, baohua@kernel.org, kevin.brodsky@arm.com, quic_zhenhuah@quicinc.com, christophe.leroy@csgroup.eu, yangyicong@hisilicon.com, linux-arm-kernel@lists.infradead.org, hughd@google.com, yang@os.amperecomputing.com, ziy@nvidia.com Subject: Re: [PATCH v4 0/4] Optimize mprotect() for large folios Message-Id: <20250629160549.da922e78d202c510a1ec68f8@linux-foundation.org> In-Reply-To: <20250628113435.46678-1-dev.jain@arm.com> References: <20250628113435.46678-1-dev.jain@arm.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sat, 28 Jun 2025 17:04:31 +0530 Dev Jain wrote: > This patchset optimizes the mprotect() system call for large folios > by PTE-batching. No issues were observed with mm-selftests, build > tested on x86_64. um what. Seems to claim that "selftests still compiles after I messed with stuff", which isn't very impressive ;) Please clarify? > We use the following test cases to measure performance, mprotect()'ing > the mapped memory to read-only then read-write 40 times: > > Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then > pte-mapping those THPs > Test case 2: Mapping 1G of memory with 64K mTHPs > Test case 3: Mapping 1G of memory with 4K pages > > Average execution time on arm64, Apple M3: > Before the patchset: > T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds > > After the patchset: > T1: 2.1 seconds T2: 2.2 seconds T3: 4.3 seconds Well that's tasty. > Observing T1/T2 and T3 before the patchset, we also remove the regression > introduced by ptep_get() on a contpte block. And, for large folios we get > an almost 74% performance improvement, albeit the trade-off being a slight > degradation in the small folio case. >