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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93022C83F1A for ; Thu, 17 Jul 2025 10:35:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EBB7B6B00B2; Thu, 17 Jul 2025 06:35:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E93966B00B3; Thu, 17 Jul 2025 06:35:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DD04C6B00B4; Thu, 17 Jul 2025 06:35:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id CB6C26B00B2 for ; Thu, 17 Jul 2025 06:35:13 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 73DC71606B5 for ; Thu, 17 Jul 2025 10:35:13 +0000 (UTC) X-FDA: 83673399306.04.3840783 Received: from mout-p-101.mailbox.org (mout-p-101.mailbox.org [80.241.56.151]) by imf04.hostedemail.com (Postfix) with ESMTP id 8B44140002 for ; Thu, 17 Jul 2025 10:35:11 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=pankajraghav.com header.s=MBO0001 header.b="PTBFI/qq"; dmarc=pass (policy=quarantine) header.from=pankajraghav.com; spf=pass (imf04.hostedemail.com: domain of kernel@pankajraghav.com designates 80.241.56.151 as permitted sender) smtp.mailfrom=kernel@pankajraghav.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1752748511; a=rsa-sha256; cv=none; b=PGg1pkxbx5Vxdbk5Ab/xE1VwPnyttjY8CsVrcXex1V17BJ073OnA7248mYKJcE4jm/1UIa JQ2RFvp1v1qAFrlgWjklA4UqPG+na05TQUeEXZgitVTzo8k6ZQQap4HL431Ek13OutJEr4 Fr79Px8mn7uTxCiALBhvufETHHBHLJY= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=pankajraghav.com header.s=MBO0001 header.b="PTBFI/qq"; dmarc=pass (policy=quarantine) header.from=pankajraghav.com; spf=pass (imf04.hostedemail.com: domain of kernel@pankajraghav.com designates 80.241.56.151 as permitted sender) smtp.mailfrom=kernel@pankajraghav.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1752748511; 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=RuP79Xyo9eJ/apZgJi9+2FlBvxVF/diDTxrd2884YVw=; b=4mHzj25i0b5+Acrz28iK97ZUCjnmflbzpt6hncVtRMV698h6Sj7iusbVsj9hl7fRtp5BVK hjixne7cLn/NgEjWoJvaVATyfqW1LlRqzPyS69R3mB2mA64IfijaYXlJWhix2qadxx7Huc O/wUUdsURtwNHYVs5mzQsl6U1tw/Myg= Received: from smtp2.mailbox.org (smtp2.mailbox.org [IPv6:2001:67c:2050:b231:465::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-101.mailbox.org (Postfix) with ESMTPS id 4bjTp30TXJz9ts1; Thu, 17 Jul 2025 12:35:07 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pankajraghav.com; s=MBO0001; t=1752748507; 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: in-reply-to:in-reply-to:references:references; bh=RuP79Xyo9eJ/apZgJi9+2FlBvxVF/diDTxrd2884YVw=; b=PTBFI/qqJGNPenVj+XFELY2yRz4Py/dcj5Uc2u5m4EWXK5EvJ1sHGngRd54qNz8owNZUAx ROuzQvf5C5VY+6OEBlGKepXpItXbJrSxcvsFTsgFSOvT+m35xpyUyeA4+6dfsBixnI0jb/ 9H3VZKjhyvNK1stDtc9of5bqJLR+rxkDSN78QbhKOW641J4/8U/H55lkRhCzuPuQrzjRrx 95ccHrsyat8to0Jhhf9c9CbImwlSboSXRPIOdIwnJ2yhNYry5teg0Lp0Pup4k6TjB1ZF3u b0010M5oo6Ve6bHo67wgiWczCQr1bjIax1dSvB+j7YctmWD3xvIzhwGfbgsm7Q== Date: Thu, 17 Jul 2025 12:34:51 +0200 From: "Pankaj Raghav (Samsung)" To: David Hildenbrand Cc: Suren Baghdasaryan , Ryan Roberts , Baolin Wang , Borislav Petkov , Ingo Molnar , "H . Peter Anvin" , Vlastimil Babka , Zi Yan , Mike Rapoport , Dave Hansen , Michal Hocko , Lorenzo Stoakes , Andrew Morton , Thomas Gleixner , Nico Pache , Dev Jain , "Liam R . Howlett" , Jens Axboe , linux-kernel@vger.kernel.org, willy@infradead.org, linux-mm@kvack.org, x86@kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Darrick J . Wong" , mcgrof@kernel.org, gost.dev@samsung.com, hch@lst.de, Pankaj Raghav Subject: Re: [PATCH v2 3/5] mm: add static PMD zero page Message-ID: References: <20250707142319.319642-1-kernel@pankajraghav.com> <20250707142319.319642-4-kernel@pankajraghav.com> <26fded53-b79d-4538-bc56-3d2055eb5d62@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: m3xpe33xpx3boi6y75ar4stbk6wdjqne X-Rspam-User: X-Rspamd-Queue-Id: 8B44140002 X-Rspamd-Server: rspam02 X-HE-Tag: 1752748511-889091 X-HE-Meta: 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 dxm7LhIP sBp851yOLxALwuwpWJkoLqQLXEn055WtthhFDj41rrC28ylwlbYLpP4P6tQqpCEgk79d7ixeF4V9hm1Px+8BBnv1xWlOsMTU8wAC6yURvmE/uoy8c3o3n//+DR7xLqChoOvTk/TTiAUG6gg/wZMFrXeHD6uPAO1ct4JW+uRnh/8jFzzbadr7GcT6kJ9DKef5z7Cwn9S0m0upw9Z1t4LMcKgHB6AAbPE3uJ5vp9+4w096S/YPMFLbApw6Fk23qr6kAsSJrKl+R9bQvz6SGzDYZ5hAG2J5FmNOa8d9nq9XsCrEqdlv9XyUvbpKlFw== 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: > > Then, we'd only need a config option to allow for that to happen. > > Something incomplete and very hacky just to give an idea. It would try allocating > it if there is actual code running that would need it, and then have it > stick around forever. > Thanks a lot for this David :) I think this is a much better idea and reduces the amount code and reuse the existing infrastructure. I will try this approach in the next version. > + /* > + * Our raised reference will prevent the shrinker from ever having > + * success -> static. > + */ > + if (atomic_read(&huge_zero_folio_is_static)) > + return huge_zero_folio; > + /* TODO: memblock allocation if buddy is not up yet? Or Reject that earlier. */ Do we need memblock allocation? At least the use cases I forsee for static pmd zero page are all after the mm is up. So I don't see why we need to allocate it via memblock. > + if (!get_huge_zero_page()) > + return NULL; > + if (atomic_cmpxchg(&huge_zero_folio_is_static, 0, 1) != 0) > + put_huge_zero_page(); > + return huge_zero_folio; > + > +} > +#endif /* CONFIG_STATIC_HUGE_ZERO_FOLIO */ > + > static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, > struct shrink_control *sc) > { > -- Pankaj