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 530D8CAC599 for ; Tue, 16 Sep 2025 09:59:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B19D98E0015; Tue, 16 Sep 2025 05:59:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AF1538E0001; Tue, 16 Sep 2025 05:59:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A2E518E0015; Tue, 16 Sep 2025 05:59:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 92DF48E0001 for ; Tue, 16 Sep 2025 05:59:32 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 642CDC0980 for ; Tue, 16 Sep 2025 09:59:32 +0000 (UTC) X-FDA: 83894666184.13.E79C39D Received: from out-188.mta1.migadu.com (out-188.mta1.migadu.com [95.215.58.188]) by imf12.hostedemail.com (Postfix) with ESMTP id 614EB40006 for ; Tue, 16 Sep 2025 09:59:30 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=d0dh7ZFQ; spf=pass (imf12.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.188 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1758016770; 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=M/74KktArckX7J8R2a2TYA4SkdsC//wm2zUbZ/9vpR8=; b=hB/7EHn5vKsfkmaKVPQU+zVgtja2tub8xRAj7sLDweQXl0TuVp8uKxlxz3S9fmb4MX5ktS b8rQLi2+cdowBqylZ0s0Gmfh5pTKzcz9i6b6SixfN/3if6DL/vgZi3FIIqlRzqbZMEyBf3 /xVTc0n8zZmEewPE5hs9cKSdS05nImg= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=d0dh7ZFQ; spf=pass (imf12.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.188 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1758016770; a=rsa-sha256; cv=none; b=VnP7jx8UxvxFXYYHMTniLx5ocEc2NhzZ8hdexQ71gf7Yq41di0O+WQ+lxR2hY+TtMItIHm bevTQ7VIP/2wo2OgS6fkJLb1bkhDOYxfA0ZcZvhYD3dkGESSHHI+EUegpSGRnibSYwPxsV 3wIxAIJBCxTpBiZ0IwwIF8JDurHexAA= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1758016767; h=from:from: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; bh=M/74KktArckX7J8R2a2TYA4SkdsC//wm2zUbZ/9vpR8=; b=d0dh7ZFQbUyeJZdVf7kyPIooDTe6AsbGuxuvJ9FbHYHYw8obeV7cLaNZ3GZIliZoEIU7Iv mkf4NPBSbfm2QryTtKxRtgzgcd66QAgfVI9kdyzQic0by6muvFPPA0Yo5QUiaCQMudOQqH XLJwkYoNLmzW3UioiLq1mWq3tQb9YIA= Date: Tue, 16 Sep 2025 17:59:12 +0800 MIME-Version: 1.0 Subject: Re: [PATCH mm-new 1/3] mm/khugepaged: skip unsuitable VMAs earlier in khugepaged_scan_mm_slot() To: Lorenzo Stoakes , Kiryl Shutsemau , Hugh Dickins Cc: akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, ioworker0@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20250914143547.27687-1-lance.yang@linux.dev> <20250914143547.27687-2-lance.yang@linux.dev> <2466c068-ccd7-41a1-bef7-6f3fefc6ff55@lucifer.local> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <2466c068-ccd7-41a1-bef7-6f3fefc6ff55@lucifer.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 614EB40006 X-Stat-Signature: ji7331p6ccb1b1mm3h88rg7q6h4enb3d X-HE-Tag: 1758016770-546305 X-HE-Meta: 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 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 2025/9/16 17:39, Lorenzo Stoakes wrote: > On Tue, Sep 16, 2025 at 10:29:11AM +0100, Kiryl Shutsemau wrote: >> On Tue, Sep 16, 2025 at 02:21:26PM +0800, Lance Yang wrote: >>> Users of mlock() expect low and predictable latency. THP collapse is a >>> heavy operation that introduces exactly the kind of unpredictable delays >>> they want to avoid. It has to unmap PTEs, copy data from the small folios >>> to a new THP, and then remap the THP back to the PMD ;) >> >> Generally, we allow minor page faults into mlocked VMAs and avoid major. >> This is minor page fault territory in my view. Makes sense to me! > > Hm, but we won't be causing minor faults via reclaim right, since they're > not on any LRU? > >> >> Also it is very similar to what compaction does and we allow compaction >> of mlocked VMA by default, unless sysctl vm.compact_unevictable_allowed >> is set to zero. > > This is a much stronger point. Ah, indeed, the compaction analogy is quite strong here, thanks! > > I think we are sometimes too vague as to what mlock() means in Totally agree on too vague ;) > totality. But given that we default allow compaction it seems sensible to > keep this behaviour the same. > > Unless you have a specific situation where this is problematic Lance? Not a specific situation right now that would clearly make this problematic. Anyway, I will drop this patch from the series. Thanks again for all the feedback everyone! Lance