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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 202F2C88E77 for ; Wed, 16 Sep 2026 00:00:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BAE666B0088; Tue, 15 Sep 2026 20:00:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B605C6B008C; Tue, 15 Sep 2026 20:00:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A75096B0093; Tue, 15 Sep 2026 20:00:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 802DF6B0088 for ; Tue, 15 Sep 2026 20:00:15 -0400 (EDT) Received: from smtpin16.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 1094816052A for ; Wed, 16 Sep 2026 00:00:15 +0000 (UTC) X-FDA: 85217667990.16.27E719B Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf22.hostedemail.com (Postfix) with ESMTP id 4BFCFC0002 for ; Wed, 16 Sep 2026 00:00:13 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=1C59dYo6; spf=pass (imf22.hostedemail.com: domain of akpm@linux-foundation.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789516813; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=lsG2UJoJMhrVhGOcp/RTa9rgqpxI7yatSzmwd8yhhxk=; b=WxYfLwoa0IFS6nFYZpfjT+/zJgcFmp321nAv1ty4SiOgJnzEhsw9Apk3IV2ope/ZuJsEXh ODzoJAhhErIZIqiG+hk8Mx6YbsiAbE/7P/hjTgca1as4MCDDbzXskXHJO36XLAvpooyEQI d+b+o3HOzdw/z+CO/7ow78pe+z0k3c4= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=1C59dYo6; spf=pass (imf22.hostedemail.com: domain of akpm@linux-foundation.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789516813; b=0Be4T55wJTq8rS1mfhWeasWsHaMN+COyZ1Nrl9tdZR8OrbwxUbhrUN7W9L8EGhaj2YQ+QW yB7bZUJYZdT2yTBr0GjVs3VplXqkluRUYon7S8DKmXfRmtiWiE0VtJN+ILrKSDTH30+24z EEuwNQwbur0VCoQPQ9262ac8lakjNEc= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 604F460008; Wed, 16 Sep 2026 00:00:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F96F1F000FF; Wed, 16 Sep 2026 00:00:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1789516812; bh=lsG2UJoJMhrVhGOcp/RTa9rgqpxI7yatSzmwd8yhhxk=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=1C59dYo66QV+RKUWZNkNSJKjp2seecbRk2ujMq+oeftUoRIcPPX+1yEcLeM93SJfK jYQVNI7P5FG0EJ4uXrKQCUTc+hoLutKaGcdEzB46e0LhpElLl6z7MS+yfZX2XV3KbF WNG9OJOwPzGbwY25294h3e7JSRzmaBn+ojJclNIo= Date: Tue, 15 Sep 2026 17:00:10 -0700 From: Andrew Morton To: Usama Arif Cc: david@kernel.org, chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org, ying.huang@linux.alibaba.com, Baoquan He , willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, Nico Pache , "Liam R. Howlett" , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com Subject: Re: [RESEND v7 00/29] mm: PMD-level swap entries for anonymous THPs Message-Id: <20260915170010.0667b6dee268fb6fb29a3fee@linux-foundation.org> In-Reply-To: References: <20260914122950.3283997-1-usama.arif@linux.dev> <20260914203237.7cdfcd4c320470f4ae5cafd2@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 4BFCFC0002 X-Stat-Signature: zte958qujw4hks6kcpejpxs1y38jxmqe X-Rspam-User: X-HE-Tag: 1789516813-913162 X-HE-Meta: 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 mFRGypVg McuNYML8k36bT+RxZPniDkDvfKtMxMuyrwXkhBgL1RVMPMX3kejzj78U9VIVmVW1PCzG/inJUqFqONfVE9gOccD7evNbdy0O5YaMrpc91HeE4tHoGxkXA7fFZiF2SmcLCHoq3tcKDH8XdmRUzfWKH59X2fNi90FvU8mABN7VOFT0/p72KhdZKyymHBvv5jUzwNg/B0dxTo5slf8BhoqiDWjNvwZhKRiPCnFTte85VoXfHq+OEGGCHyldQWA7AaSeyvsvy Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 15 Sep 2026 15:09:16 +0100 Usama Arif wrote: > > Four workers repeatedly write the working set, forcing memory to be > swapped out and back in. The results below are the medians of five > interleaved runs per kernel, following one warm-up run: > > Metric Baseline median Patched median Change > Aggregate benchmark throughput 584.3 MiB/s 2,408.9 MiB/s +312.2% (4.12x) > Elapsed time 85.43 s 20.72 s -75.7% > Major faults 1,814,699 228,466 -87.4% > Swap I/O rate 1.02 GiB/s 4.10 GiB/s +303.9% > > The results look good as this is a swap-intensive workload. > It primarily demonstrates the reduction in swap-fault and page-table > overhead from preserving PMD mappings. > > For long-running workloads, where I believe the series will shine, I expect > benefits from fewer TLB misses, less khugepaged work as well as less kernel churn > due to larger folios, although there aren't a lot of benchmarks to test that. > PMD swap entries also move us closer to eliminating page-table deposits for > anonymous THPs, which would provide memory savings. > Thanks. Wow. This doesn't look totally real-world but it's close enough to indicate that real people doing real things will see nice benefits from this change. As expected - leaving post-swapin thp reassembly to khugepaged was so lame. Please add the above info to the [0/N] and maintain it. (I'm itching to get this moving ahead, but we do need eyes on those core bits).