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 48CB1C5DF94 for ; Mon, 24 Aug 2026 03:53:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 274746B0095; Sun, 23 Aug 2026 23:53:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 224F66B009B; Sun, 23 Aug 2026 23:53:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 115BA6B009D; Sun, 23 Aug 2026 23:53:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id DAA466B0095 for ; Sun, 23 Aug 2026 23:53:02 -0400 (EDT) Received: from smtpin08.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id D6EFC1403D2 for ; Mon, 24 Aug 2026 03:53:00 +0000 (UTC) X-FDA: 85134792120.08.CEE748E Received: from mail-qv1-f54.google.com (mail-qv1-f54.google.com [209.85.219.54]) by imf14.hostedemail.com (Postfix) with ESMTP id 19EB2100003 for ; Mon, 24 Aug 2026 03:52:58 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=gourry.net header.s=google header.b=frR+91zz; spf=pass (imf14.hostedemail.com: domain of gourry@gourry.net designates 209.85.219.54 as permitted sender) smtp.mailfrom=gourry@gourry.net; dmarc=none ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787543579; b=JrZwa+XX5n4msuYxeM5NjrBxYo6TNBPCA25kRlMHUmBMti2J0/+SLEF2uxDYA9wXYpcUbr 3QsEmf7UhEzF3oV5im09zA8TtjzMD78S2vnn8geczp+jxSc/iqmy51ZqNYGgiibsYKYtcR wyD7WPpYDcHb4JldQCK9arR3SyzMhbk= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=gourry.net header.s=google header.b=frR+91zz; spf=pass (imf14.hostedemail.com: domain of gourry@gourry.net designates 209.85.219.54 as permitted sender) smtp.mailfrom=gourry@gourry.net; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787543579; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=+NkwZvgRmwHRjzupt0N+f3fvk1vj4jZO7Q0jmTyKYe8=; b=WJ3TRmcBMXKmXFSyxIzvvOYOEHXYahbpn1YrzoBPJYH7Q0IM4EwQ29BwN2bWenBogW5I8J FESnXXkQOnDvC8bSUufTLdt3q+yUOitAk7swEJlakigzanawJCX+Kl+u7Hy+nko+KnmkRw EqMXNaaXES7K6SITeBY3FeCArGiBkfs= Received: by mail-qv1-f54.google.com with SMTP id 6a1803df08f44-8fcc43c48f7so35370586d6.2 for ; Sun, 23 Aug 2026 20:52:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gourry.net; s=google; t=1787543578; x=1788148378; darn=kvack.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=+NkwZvgRmwHRjzupt0N+f3fvk1vj4jZO7Q0jmTyKYe8=; b=frR+91zz7u+JTN4rEAgF70btPoC/onLFsyPoII7nKioQE7T8tWxuEq0YYc7yLGYLMi TympuPXcwDkh03Arb3tkKBtCGM1lg64/3kEtKZd/Nih65IXLmXSOZhPpYSaNtj39FcxF WkdeX6b7TP/g+4BIdvKs4irOMD75AeZfbxKjWD6NLy8dlMJREyXpqJa9PdauZKehyC8s ML2rHM+TAEjAg/rhBUYdTXD4FD6DpBAiOJUg0u9yw6cRdAK8FIwej3fq2ecjwnj3pJHQ Ppsf4+menlVrqUpoDqNnmLa9EFgjEBDNPOt3icU8F4/qMQU0LowRMeJ8NOv3e2edo68q 7xfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787543578; x=1788148378; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=+NkwZvgRmwHRjzupt0N+f3fvk1vj4jZO7Q0jmTyKYe8=; b=lihI7YeGi3uZ275QFsrF0XiB5D937Nb0Vq2pEgHhJ3Jh3h9Wt833bxVPc/wsF10Ekq bc+YiWJGoZo8WArAqkbI/23ammmFoH6svESSWZ3vD5YDgoDOy9sJbsm54mgWTHKbakLs MVr427MKPa7eZQiqE73Gl5EvSn0/T36lxDCXxNIH+Wrp4lLAaavQcsOB+YeShkN8Fznb CGlkVcu73GyG5ff2DBcPWvQbf1bDBX0RFY/HLjVDwwdi5RxlOIGD9Cx2OI8cZi9ryh0y boUQcfUJ5cLdJk6AEX3rbMfb1HWeucwthAwBtmITWQB7qiiO1m59sYjlD3Wz04rjVgyW tsRA== X-Gm-Message-State: AFuF++l0QmbCiXbRn6Idwk+6svNpvZ1/LaEsAHtIkXjVFGIJ6soGqabB ztP1q99+Zp5k5Yy+Kdlt9imfXl3mNpcRMEaqHqPyvWTGcUfR1gACglbyJ9GXqRX5vMw= X-Gm-Gg: AR+sD12pHJsdf1FZmP3av7/E8LsW5h/P+mkNN29upZfST/RBmCPEoY8QrZ+ne58qFWu mAW/P/d9OAsUpnIbMngBiN81gmd5JIxtbzF1msGV7bVwwTmIvLGVXnbIPtVr5AeZJH2cMUJJcFQ pvEbXIEgFem+cuzryp7avuHRgLjGe4yZWTWn+bZmVVD7nriDenMr0y10lcAwkdQywH/EiMwiGZq oSs4jHm6kit3ZcorhESnjrtfkCv3RnBDoAIryiSfb3H+w7HPqU/+EsesEneGHbVz3jC6Rim5CbB jJl3L2pO55l2Eb6TVV2EStVedZDWa6bjlVzaVrPrWNDU/07kogC1jQYJF/eNkF/eXBhcoS7inF1 Xy/jlF7NqKe6qrkN1AEtx3cC7WfLCfn2ltW+4DH4oybXHeDZ5VV3cAM6FgD5c4yO8hdTTYbdvlL 2KvZHIOyQAQzA+1YkvxhlXAJKQIN6X75MmT/AJfZBeMqZAN/w3zOOrDe8bVq/gFRzPiuRrHc+8F /Pzu7BDyHphJCLzlvjGwM2U+UmLpYwL54kMluVg1QS/ X-Received: by 2002:a05:6214:860a:b0:907:d89f:f9ce with SMTP id 6a1803df08f44-90c8f95710cmr155411406d6.12.1787543578189; Sun, 23 Aug 2026 20:52:58 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F (pool-173-79-60-52.washdc.fios.verizon.net. [173.79.60.52]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-90c9393203asm51021056d6.23.2026.08.23.20.52.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 23 Aug 2026 20:52:57 -0700 (PDT) Date: Sun, 23 Aug 2026 23:52:55 -0400 From: Gregory Price To: Matthew Wilcox Cc: linux-mm@kvack.org, akpm@linux-foundation.org, edumazet@google.com, linux-kernel@vger.kernel.org, kernel-team@meta.com, stable@vger.kernel.org, david@kernel.org, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, syzbot+0dbf6d295b3350944f0b@syzkaller.appspotmail.com Subject: Re: [PATCH] mm/mempolicy: refcount the weighted interleave state instead of copying it Message-ID: References: <20260821104043.f692421fec915c0c5bc1fbe6@linux-foundation.org> <20260824024117.1755899-1-gourry@gourry.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 19EB2100003 X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: p7dh4wkefyf73dexrzi1cgdsgtuus819 X-HE-Tag: 1787543578-476405 X-HE-Meta: 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 WXuQPhX6 WHMTQRpwdXUY1HRoCnU0Ao5F7XWXRi50QIRjtQJRXdeB5HuPA82Fkgu40gfTY0IHuh8DW3Q0UIXTJwoHZyvk731fOzYNbm41a4Y8MKClnUje3a/azA0e6TD7XJDWH3LzCXJOhQQSnY+Hs9TEEPzYzdHx5CgIG97GdUhm8RQ78Hl0Lz+7/Z/qOHnswC5hSCAGL+nE9Jx2IDz7STRDmIfzW7M3MOS7jid7F4iKH38VxEhjWi9eKbd1AgAtIKim1J+x+z7pr5tK4LBGMciQJzh78VhwfRa7Mb3hRfLSWip7U6WMEh9C+jt0eA8nsQKxCn1N+H98hoKUvEeMlX0sn26L6L85YpFHfUJRWQFO1WtPYbFsFXXv7o6U9GUlU9nFVdcaMB99Xzp8ON1B0HPnPUm6gVgvAf7Dp3X42nzm1mVRwC63BxFuC0vLwsJ6nDXuKdGYf7VXV4j9x7kRDRS8a7CNbHB0k2A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 24, 2026 at 04:06:03AM +0100, Matthew Wilcox wrote: > On Sun, Aug 23, 2026 at 10:41:17PM -0400, Gregory Price wrote: > > Bit of a shame to take/put a refcount on every memory allocation. That > seems like it might hurt (even being on a different cacheline). Would > it make more sense to use SRCU for this? Bulk allocation - from some measurements it's about once per 100-pages on average. Looking back at the data I was getting about 41 refs per 4096 pages (16MB chunks). Have to imagine there's other cache fighting in that stack too. I'm less familiar with the rules around SRCU so i shied away from it, but I will take a look. ~Gregory