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 D714BC61DB9 for ; Fri, 28 Aug 2026 12:41:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B21F76B0088; Fri, 28 Aug 2026 08:41:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AAB9A6B008A; Fri, 28 Aug 2026 08:41:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 972C66B008C; Fri, 28 Aug 2026 08:41:17 -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 7293E6B0088 for ; Fri, 28 Aug 2026 08:41:17 -0400 (EDT) Received: from smtpin27.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id EB5E5A3BB5 for ; Fri, 28 Aug 2026 12:41:16 +0000 (UTC) X-FDA: 85150638552.27.BC8CF09 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) by imf05.hostedemail.com (Postfix) with ESMTP id CCEA0100003 for ; Fri, 28 Aug 2026 12:41:14 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=infradead.org header.s=desiato.20200630 header.b=HzpcEx3Z; dmarc=pass (policy=none) header.from=infradead.org; spf=pass (imf05.hostedemail.com: domain of peterz@infradead.org designates 90.155.92.199 as permitted sender) smtp.mailfrom=peterz@infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787920875; 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=JsdYFNlmu3mZtC0DhffCWqMCuB12dqERlIoFUoVuPCg=; b=5PRPrwYbI1BBX+7kBr2O8vzIeOWflUUTQX3gKNdjYT0LoBL89r71fW7sDwj6oYHk7i3NIX /iIBsZrQQcf4SCGq3yJW9v8YE4rGZ5cNaNxkFkd8r6CqEW2+FsFAp6JmbaKwhMhmK5eI/r LGWL0UxQNAXjXIHPgdIrrT7/v3Ef5jI= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787920875; b=7CTvbLntEvaFyfH3bq4hkoRoEC9RH/uGa1Wk888b1mbZb7CwD8yR/Urfwk13Kdhl6RUyQy /eChTknSFyaZ+JKBqRCUsRVbkny2P29hlxcjDoKzaUNBs0qktoZJfJPa9CGABb3uChFbx1 pSXkcwD7CpGgGTwUv2a+d6zI/E9Gbtc= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=infradead.org header.s=desiato.20200630 header.b=HzpcEx3Z; dmarc=pass (policy=none) header.from=infradead.org; spf=pass (imf05.hostedemail.com: domain of peterz@infradead.org designates 90.155.92.199 as permitted sender) smtp.mailfrom=peterz@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=JsdYFNlmu3mZtC0DhffCWqMCuB12dqERlIoFUoVuPCg=; b=HzpcEx3Zje4gJfUb+ceU/x1FvE Zl3Mh4+eWu1HIJa93GBWDAjBGZo41IkX2S3AHDLV+ABH8Iudi6x4SUr8JFb7Xp+1f8Ta90NUfIQpx xATI1wocphSZX/9LCrdJL9vLsfbJVD4ikAX0dnigoFCt2X36M6tqukfVSkYUTSw7/RpzWURd7G2B7 ky42+wb5W0wgO3bhKN8rW0nZqed7CeNX1TYQw6coaPu0LDtCbvXRJ5cNfOXMnNwCO/uM4nFSEQZzM jAGWSRVFbt1xFQbORlb47ptVlPQUcPizFCQgguncsUiMarbI0Ol/17cCxaQrLbrIovxFgxl4kOQLa mZsBqG5g==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.2 #2 (Red Hat Linux)) id 1wzvtH-00000008FbN-2c6I; Fri, 28 Aug 2026 12:41:04 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 07F9C30030F; Fri, 28 Aug 2026 14:41:01 +0200 (CEST) Date: Fri, 28 Aug 2026 14:41:00 +0200 From: Peter Zijlstra To: David Stevens Cc: Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Andrew Morton , Dave Chinner , Qi Zheng , Roman Gushchin , Muchun Song , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Uladzislau Rezki , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Sebastian Andrzej Siewior , Clark Williams , suleiman@google.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-rt-devel@lists.linux.dev Subject: Re: [RFC 06/10] Reclaim memory from blocked kernel stacks Message-ID: <20260828124100.GO687043@noisy.programming.kicks-ass.net> References: <20260827232948.2520558-1-stevensd@google.com> <20260827232948.2520558-7-stevensd@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260827232948.2520558-7-stevensd@google.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: CCEA0100003 X-Stat-Signature: hx81wycr9iizira9aadsnzpu35joc1sm X-Rspam-User: X-HE-Tag: 1787920874-16234 X-HE-Meta: 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 SQx2m0tb km1m6nOQtDmS9LsR1WLib6QWV9eZvr6h9KxUvMgiiONS9k0QzIXyzVkwX9s6ED5gkEf87VebVg9IKsHprGITCzMLUWvtrzR9Uwia3PaNN1eGLEwPs1zatXpJAC70GwneLjhBPQYnViuDBeonaU9sFIQIBtvWVKLNemGwYlgTxK6Lqd4/JefZbVJEUseLpBP6+yJ14zj5y3j8MiAxUY7VUnk/DIsCbDzl/k57lUdxiCAcFhNM= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 27, 2026 at 04:29:44PM -0700, David Stevens wrote: > This feature does work on PREEMPT_RT, but is likely undesirable due to > the extra uncertainty. The fact that alloc_pages_nolock_noprof() cannot > be called from under the scheduler lock also makes repopulating stacks > more expensive. Aaah, so you knew it was hot garbage :-( Please don't ever post anything like this again.