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 C05CEC5DF74 for ; Tue, 18 Aug 2026 14:23:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D17236B03B9; Tue, 18 Aug 2026 10:23:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CEEAB6B0452; Tue, 18 Aug 2026 10:23:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C032A6B07B4; Tue, 18 Aug 2026 10:23:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 98AA96B03B9 for ; Tue, 18 Aug 2026 10:23:36 -0400 (EDT) Received: from smtpin09.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 40C2A1A02CE for ; Tue, 18 Aug 2026 14:23:36 +0000 (UTC) X-FDA: 85114608432.09.FF38DA7 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf01.hostedemail.com (Postfix) with ESMTP id 64AEF40009 for ; Tue, 18 Aug 2026 14:23:34 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=j1b6Dg3a; spf=pass (imf01.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787063014; 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=h880+CPRpSv4AV1jDBV+Jr+Z/juMTH5NojBRxANXwVA=; b=Xd+85mLJAkmEWaV7opXh8ILQK0OZMmpckRK0RwJ0HMNTr3VAiP16fzyuQfR4KjvCY0U2Vl dOT5sUY0TkXdQWE4JS13nHJkXAJ3sdntrdpHBiQ6UYrvy8lePWLXfU+YL77fPnMlyedbeY VZxJeJ6eEM6K4RRjsusz0tBDtRt7Yu4= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=j1b6Dg3a; spf=pass (imf01.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787063014; b=yVGzrbSkf17Hw6mGWtM1fyI/M4Sgi4K4DxUIYtm/GqSQJLOD2TGRGDH3tyt9XJVlLkZnK1 gx+k5hqENzDw9pgmFJ+r4xcGL+zOdvnHo5eufEF3TAI2ONtBTODR6Xg6HhpomOnci/8jsE 1vqWB1HKCOPc26A7lQ5PKvdZEZ46cIw= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 3F1AF43A00; Tue, 18 Aug 2026 14:23:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6DE1D1F000E9; Tue, 18 Aug 2026 14:23:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787063013; bh=h880+CPRpSv4AV1jDBV+Jr+Z/juMTH5NojBRxANXwVA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=j1b6Dg3aZ/8bvBGwgc+wHk+4pe/7FqbVkNBUpIkinH92Sq48jGFvgW0PvZY2EKP4F VPi2slutiS03hYcTkO4b7VMDL9Cy4029nQqHht5bAltYO35DZbpHQhxaYDfkdGXmyU d7mp2SrQrrIBQ9zjdrlp858WDIS2AB2TdP8OLDLDYPgpkN060waU+EelgU14pAz94+ EEgTaG60FPSDCzubaikqveSexJSCIBQ/7a6cH1W0+TV/nKQCEokV6McdnNHbo1rqTm PT2T3D2Py9wQFVCHs4iwPVWc/41mgPfCbIOTSZ38TD/AhtiAHiPRevutGTGeN3HawO 1vGbxP7bvcjXg== Message-ID: <3dadebb3-7e2a-459c-a5e8-b375faf89938@kernel.org> Date: Tue, 18 Aug 2026 16:23:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hugetlb: add cond_resched() to __unmap_hugepage_range() To: Leon Hwang , linux-mm@kvack.org Cc: Muchun Song , Oscar Salvador , Andrew Morton , linux-kernel@vger.kernel.org, Lance Yang References: <20260818135029.93288-1-leon.hwang@linux.dev> 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: <20260818135029.93288-1-leon.hwang@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: fgq5hy7odcuezffwrby6cczywh31p6cf X-Rspamd-Queue-Id: 64AEF40009 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1787063014-248006 X-HE-Meta: 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 DYohMPZU kWEB1n7SeJoRXgOhaA+dCfloi/yldAk+4W8jlDTMQ8QyMzPlf9fyNPbmYs2s96K/Y362Z9S9xgzw+N7IVsRooqFm5h81TsvZntPB/cA4BAVJ8MfHj7LL2wDCAdSp1hqU4iC8tENeQqStNz+ACq/8jgew6yjpr32bZoqDsINjt4ImzPiORjB83W6Q1QNqgqPLz7jdyUxzp9p3bLVLjcIVvaQ6WNUKvh7q5IM0UcENKWjoavKFV+XvkQkWa2jNwlQoTZMlNHCKXs5mqVOQFY029NXfFYcMzpuAzp2ZkYHbV7pwCfNovfdBwe9SeqLV6Kh/grqr91zre7uYIIgEug5sJF/Cbfm6DCK18mJbCFZXoiRq0iUY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/18/26 15:50, Leon Hwang wrote: > Packet receive timeouts were traced to sparse HugeTLB unmapping in > production. A task unmapping a sparse 2.5 TiB HugeTLB mapping could > remain in kernel context for over 40 ms without reaching a scheduling > point while walking empty huge PTEs. Although hard IRQs could still be > handled, the per-CPU ksoftirqd thread and other runnable tasks could not > run during that interval, delaying NET_RX softirq work queued to > ksoftirqd. > > Add cond_resched() at the beginning of the hugepage loop so ksoftirqd > and other runnable tasks can run between iterations. Testing with > PREEMPT_NONE showed that the maximum interval between scheduling points > fell from over 40 ms to below 2.5 ms. Total time spent in > __unmap_hugepage_range() remained about 36 ms. > > Reported-by: Lance Yang > Tested-by: Lance Yang > Signed-off-by: Leon Hwang > --- > mm/hugetlb.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index dded1768193a..0a91aac2369f 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -5233,6 +5233,8 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, > last_addr_mask = hugetlb_mask_last_page(h); > address = start; > for (; address < end; address += sz) { > + cond_resched(); > + > ptep = hugetlb_walk(vma, address, sz); > if (!ptep) { > address |= last_addr_mask; As Michal just put it: "PREEMPT_NONE is effectivelly dead and most cond_resched will/should be removed. Is there any reason why you are not using full preemption when requiring low latencies?" https://lore.kernel.org/r/aoRnUxUlgf_kRlm8@tiehlicka -- Cheers, David