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 C9B39F99362 for ; Thu, 23 Apr 2026 10:27:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 15A8D6B0005; Thu, 23 Apr 2026 06:27:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 131856B008A; Thu, 23 Apr 2026 06:27:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 047616B008C; Thu, 23 Apr 2026 06:27:47 -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 E7CCE6B0005 for ; Thu, 23 Apr 2026 06:27:46 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01b-stub [10.200.18.250]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 81E59C1FF3 for ; Thu, 23 Apr 2026 10:27:46 +0000 (UTC) X-FDA: 84689444532.10.4096228 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf10.hostedemail.com (Postfix) with ESMTP id 99560C0012 for ; Thu, 23 Apr 2026 10:27:44 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Ok0FWBV9; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf10.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1776940064; 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=DYciIbNdyiRbKvhar5Z5BIvyOIoUQHLiqms9/u4o9nc=; b=eXOMYUEuE2KN13/2yrf30Pow8ZCf1zm4h98f5rRipatVWAMGqce1OZqFXGog4WDAF6EMSn rP+EJ9osp0rwl88P6jiAUI1gN+KxqDfye6F0lZjNOtIcV/AEi/p1j+xSas2sObnc80vSxN +dgNUToGetSQLvCK8PcrCUMRrR+ngrA= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Ok0FWBV9; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf10.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776940064; a=rsa-sha256; cv=none; b=wUzSZft0vh+V0QkO36wLdL/nNp985nNfO6tMet6G1DWlCU/dC5QSU4vIBKMcH2ScWsJhLa SqkDDrA6TR8owvBkaYCxnEnpTy7c5w13s1e9n4UV9vzU3cgcERAyw4pxGkZoEVNLgBWG+y PjRgMQ8E58uaF4uNj0QFvM3SS5PbOKk= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 9186844245; Thu, 23 Apr 2026 10:27:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 49A32C2BCB2; Thu, 23 Apr 2026 10:27:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776940063; bh=ohdrzIDtFsxHqFS1uvIA5YEDv/bmIvcy1gYpoCoGLJs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Ok0FWBV9PjaTvb9k3tr/bDRO6Bnnsc5r+cgS9c9qb/7vQfS0+dSOy9Rhhpma670eK PX9YCMfDqd4gmFY6VQato7wSoq7iE1xqskFmOMog+FRyLSOY+49eUis37C35malsu/ 9B9ClLYJQTB+0Rk7cmDKNvPeivYtFZP5C0dLcF20QRwTP1x+v9OTW1C1K1CpmJgm3X MROFWVPtcda7rBtLde4TYsImG789mMEZ1xNqs60HHc+UyxIWEDbrS/8wbOdi25muTv F6w1qd/TUuT1/vyNDIoSTR77NjQY194gE6mQFJ+qXhwK35pxVoty+bROtnfsoq6DB8 2yJwECD0NCVoQ== Message-ID: <76191a17-18bf-4e9b-9ab5-dc9a48abfabb@kernel.org> Date: Thu, 23 Apr 2026 12:27:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/5] mm: Introduce zone_appears_fragmented() To: Matthew Brost , intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: =?UTF-8?Q?Thomas_Hellstr=C3=B6m?= , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner , Michal Hocko References: <20260423055656.1696379-1-matthew.brost@intel.com> <20260423055656.1696379-2-matthew.brost@intel.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260423055656.1696379-2-matthew.brost@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 99560C0012 X-Stat-Signature: y84fz6eet7mh9siq8b4y8sdkbod15jmf X-Rspam-User: X-HE-Tag: 1776940064-197278 X-HE-Meta: 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 Uc6pstdu 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/23/26 07:56, Matthew Brost wrote: > Introduce zone_appears_fragmented() as a lightweight helper to allow > subsystems to make coarse decisions about reclaim behavior in the > presence of likely fragmentation. > > The helper implements a simple heuristic: if the number of free pages > in a zone exceeds twice the high watermark, the zone is considered to > have ample free memory and allocation failures are more likely due to > fragmentation than overall memory pressure. > > This is intentionally imprecise and is not meant to replace the core > MM compaction or fragmentation accounting logic. Instead, it provides > a cheap signal for callers (e.g., shrinkers) that wish to avoid > overly aggressive reclaim when sufficient free memory exists but > high-order allocations may still fail. > > No functional changes; this is a preparatory helper for future users. > > Cc: Thomas Hellström > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Lorenzo Stoakes > Cc: "Liam R. Howlett" > Cc: Vlastimil Babka > Cc: Mike Rapoport > Cc: Suren Baghdasaryan > Cc: Michal Hocko > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Matthew Brost > --- > include/linux/vmstat.h | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h > index 3c9c266cf782..568d9f4f1a1f 100644 > --- a/include/linux/vmstat.h > +++ b/include/linux/vmstat.h > @@ -483,6 +483,19 @@ static inline const char *zone_stat_name(enum zone_stat_item item) > return vmstat_text[item]; > } > > +static inline bool zone_appears_fragmented(struct zone *zone) > +{ "zone_likely_fragmented" or "zone_maybe_fragmented" might be clearer, depending on the actual semantics. > + /* > + * Simple heuristic: if the number of free pages is more than twice the > + * high watermark, this strongly suggests that the zone is heavily > + * fragmented when called from a shrinker. > + */ I'll cc some more people. But the "when called from a shrinker" bit is concerning. Are there additional semantics that should be expressed in the function name, for example? Something that implies that this function only gives you a reasonable answer in a certain context. -- Cheers, David