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 77C79CA1005 for ; Tue, 2 Sep 2025 18:59:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7E8D58E0002; Tue, 2 Sep 2025 14:59:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 771A48E0001; Tue, 2 Sep 2025 14:59:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 639FD8E0002; Tue, 2 Sep 2025 14:59:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 4DAC68E0001 for ; Tue, 2 Sep 2025 14:59:39 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id EDFC185197 for ; Tue, 2 Sep 2025 18:59:38 +0000 (UTC) X-FDA: 83845224036.28.FF338EC Received: from mail-ed1-f45.google.com (mail-ed1-f45.google.com [209.85.208.45]) by imf09.hostedemail.com (Postfix) with ESMTP id 3A0EB140006 for ; Tue, 2 Sep 2025 18:59:36 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b="n+nfXo/5"; spf=pass (imf09.hostedemail.com: domain of lokeshgidra@google.com designates 209.85.208.45 as permitted sender) smtp.mailfrom=lokeshgidra@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1756839577; 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=PO6uBrgZrvwvFD9Y2iG++L1mUkkDAtsEspEBPhAeKaA=; b=IJPmTNEJHmALOL9YmB82ijulyHuklJpvxvXpOqDSzmLekTCXeQlihMiDBRSXNNsqTx8XP3 rmKq1J2E1Mex5EWNtvQph6Z78mNeBXEXTZwDZE2wtu+WQ/UX2S1M7eNudaAMuQw7Hf1gyH rTFPgA37hQXlgpimghjPLVymMP80tSo= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b="n+nfXo/5"; spf=pass (imf09.hostedemail.com: domain of lokeshgidra@google.com designates 209.85.208.45 as permitted sender) smtp.mailfrom=lokeshgidra@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1756839577; a=rsa-sha256; cv=none; b=qIQlcJz4V72XH4m9Jhj9XbO90aTVWK3qHs68XnhX8oxVteKqi6DwEpKKixe69mcIm8kER1 XkATE7pQWdECN6uIqL2KWlIHspbRKXpYub01Xrv7YHlxrUav/yF2mvgPp3clL3ay9EaHq7 LFLu3nN0HK6E1ixQLS6LQ+D+3CMKBB0= Received: by mail-ed1-f45.google.com with SMTP id 4fb4d7f45d1cf-61ed395ba46so3186a12.0 for ; Tue, 02 Sep 2025 11:59:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1756839575; x=1757444375; darn=kvack.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=PO6uBrgZrvwvFD9Y2iG++L1mUkkDAtsEspEBPhAeKaA=; b=n+nfXo/5F9EAJHcv7/BqxCRVdkdjLH5INC0KXU2U8oBAbDIjtg142Lsb+sqFtW7ydX J/AdRG4hAZpc0eeXoDAubsVndSsJq4+0PkrX1UHRijso+/UPse2sc2o0ME6WvgG3gi6x U0T49W1sge+cbt3PaseurZXEoS7S8JBaTQ1TtPGQW1GKwzyyw88vYiHQNxIXFtiuOXnu TV2yo6YcZB6sFAu2UGeUJ7S9sgmyM+OT5HeCz0kMC0Eds5TzwccYhHTXXu5qJzK9ZdnB POvCx0cu1Ho8V8JZiKu1gnlNAYzEoxS6WG1F0LxX9xxJIbA+DWypA6JgFi4PzlWX4Sxu kujQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756839575; x=1757444375; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=PO6uBrgZrvwvFD9Y2iG++L1mUkkDAtsEspEBPhAeKaA=; b=bKsXtFGS58mikgMgimNCtvHHE7dBqV2AP7TVGWTrAztbR2Nh8LuYg/p+YJxHHkkiVe xFsLm0lR3jB+rOlz2Bqs7DMkBLifIjj2YvA+axXKWZQ39SzJ3x8kDCB6vAvPEKGvd2Vm 60Ncpxd87PrIBbEEzBkHMCG1L5kdAL+9WC5OZuz+82A/sWTpZsyRhg4AAUXBg022rJZg k+KQncsrw41/GVvX7gf54e+XnML8WpFtrj78HTHzgX7HQz8XnLtv1ilMvSrgLtq7psXx z7X78kVTDbAD23RyNSDSu4XfJLIcD/1tdam7jot7JovMr5RIs5GZkgHTtyKY6h14ABNU ko3A== X-Forwarded-Encrypted: i=1; AJvYcCVAEy0u6MtqQAkm+u7x6M1x0Hea3V+XbKqX732Cj9f7Knt1Qj/HIzOaF765zSssnId3MJOiXiKyWA==@kvack.org X-Gm-Message-State: AOJu0Yz+Y2kcQ/sphsnGsJ77Ejs+TdROasXyRbWrulpszH3OY/OBZ1fL hjd5d99XAKtTG8B5DTigm0pW1I7FPJTgLb6SCC1nJUMdBH3xCuvDWSZjZL2DR91ALA0MVhCydF6 qH2GB6HBCWJbESgKvJP5PRPo3OOmo+3W7BY4UyJAw X-Gm-Gg: ASbGnctfx7NqgqPzZv0+oyHxkh8xKys/vWGcQt6y8XLjB+4Z0WDuESxt3Y3yB+UwWYX pGaiFxGtyAY3k2QK9cAOZAjPe1uIF81Jjsf07ljEHqmzgQlrCT22tkH8FOBFAMDqTu4G7IbmhLs eETq4u8YHKSPrX3wzSKRgS4Qgq9x+vSoYJfy+eU+C/A484+yX+xf0AtMNiG/+KYMWUrOsiYgKcz fPuDzX/SanQPdXhxA86833WZF3LwajMdSJC4a6gR1N+ X-Google-Smtp-Source: AGHT+IFjfqil45P3xLPeX6vA2o1kgdJcuyVtGZnjUPClXaZBLSK1c50QtoACsnaFusJcVUUuKEVNu0qgZ5/GvOSAzPo= X-Received: by 2002:a05:6402:2397:b0:61c:1dbc:67a with SMTP id 4fb4d7f45d1cf-61d21f059e4mr215637a12.3.1756839575381; Tue, 02 Sep 2025 11:59:35 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Lokesh Gidra Date: Tue, 2 Sep 2025 11:59:23 -0700 X-Gm-Features: Ac12FXyu_JdCq7fD2tQ0dRu3q6Is8GLBBBqLQORpRzSbl-I9vnpCRz2PF9AzEko Message-ID: Subject: Re: [DISCUSSION] Unconditionally lock folios when calling rmap_walk() To: Lorenzo Stoakes Cc: David Hildenbrand , Andrew Morton , Harry Yoo , Zi Yan , Barry Song <21cnbao@gmail.com>, "open list:MEMORY MANAGEMENT" , Peter Xu , Suren Baghdasaryan , Kalesh Singh , android-mm , linux-kernel , Jann Horn , Rik van Riel , Vlastimil Babka , "Liam R. Howlett" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 3A0EB140006 X-Stat-Signature: s747ouc8j4oze45kfb9hqzezk59isj7z X-Rspam-User: X-HE-Tag: 1756839576-670268 X-HE-Meta: U2FsdGVkX189LP/X/E9lZ9O9FM9eygU49Y39EJ9+Oo8jOnaVyktOw2hwn3MUVuivXI7g2/qyBd/RhrJcmJnYQfS4K6XVtyS+FMfMjk7+xfTVbe+74I65Z2XNNoYZ6s+SYfCZNQcp62Jrp16qAd7wCKdyAbzY0ujXMbYzAEa/Hynti/Mh+fZnjkfZeITJwZGLJFlRa6vBLsmgOTL9rzJ7JOpvMy809CfAlM9F3tayZI19/a8a0JZzvwvshC4qhFhpp4b64Taeub+GBKY3+nl/1UrlCJO85vdU+sxIZP0EIWznJ1dy+6IDUYAKiOOwaI51m5PIo1qfn7Y4DBBgGZD57NpFl2eDMXvB1VOe1mDpdY19BwTQxXknQL5Thl0nPndIe7afyDGSLhpAqtH41CompQ/cfPOZbBIdKR8OZNSBvrhzGQJz3U0ZkTZaBZXr6Tl85FEJIPOq5qf1bmACLfsgATPQXpQtDzx9SGXocp/NEDhXzOM1B9MQvOD1dHzImg++OycOTa9Inxay4bQaXhaCHFdHb/OPPL1WntKbvTmmGjqSjiFXC0OkmLSh4BmBVQtYRrjRaTYURy3fLGwFhtIJStPVt76J1narbtkmE1o7yIdcgCYliHjTdFuEuqjbgtg6v3PcWtLGC8LksUaet6SWi0/OaCEXV91XMQrvyCUiX/5JQkjpyQwYBwc+rRaO82PLPqMU77Bk7hfAzMNHnSTwnuk2Q01DgAj12uu+TUpGY2zHwuu+Ohv1yu/NbxU8SLOsRDGgLWbKhgyhhvILCBQoYlq2Z1tspqo9psNw+nDZGKzJophlyBvhy5Gm548TUIMzGMcXWzTIzVqj1gyz2wup7acUHGPVpiNV+Q4f8mFLLaoejDUxFz6Xd5/xfWKlJAj/8oEdJf8UMvvl5zHK/K9pkCdG7dP1kLeDuhv+cVoYzf1VSokukA7XEhPFcmEyBWBEUlFunTDriPU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Aug 29, 2025 at 2:04=E2=80=AFAM Lorenzo Stoakes wrote: > > On Fri, Aug 29, 2025 at 10:42:45AM +0200, David Hildenbrand wrote: > > > > > > > > I do wonder if we can identify this case and handle things differen= tly. > > > > > > > > Perhaps even saying 'try and get the rmap lock, but if there's "too= much" > > > > contention, grab the folio lock. > > > > > > Can you please elaborate what you mean? Where do you mean we can > > > possibly do something like this? > > > > > > UFFD move only works on PageAnonExclusive folios. So, would it help > > > (in terms of avoiding contention) if we were to change the condition: > > > > I think we shouldn't be using PAE here. Once could consider using > > folio_maybe_mapped_shared(), and assume contention on the folio lock if= it > > is maybe mapped shared. > > Interesting! > > > > > But the real question is with whom we would be contending for the folio > > lock. > > > > Is it really other processes mapping that folio? I'm not so sure. > > Yeah, I might go off and do some research myself on this, actually. Nail = down > wehre this might actually happen. > > Generally I'm softening on this and maybe we're good with the proposed ch= ange. > > But still want to be super careful here... :) > Anxiously waiting for your assessment. Fingers crossed :) > > > > -- > > Cheers > > > > David / dhildenb > > > > Cheers, Lorenzo