From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6D6403BC668; Wed, 27 May 2026 10:06:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779876373; cv=none; b=nBNcmQNMTk1VEYskUqMmfSWlYTrSqQp1M2bZek7SIv6JBehsrKFVkq4rSHD68bJ6eMZMYE8fJSkB5/tzFAoiEwSF6er1QtUPvSo1+RriTFZEewpH3xR7ZeOapN5xyT32iFUNIljgrhXWYwvsNCJoKSBqckwsmthVGMdZpB1J2fI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779876373; c=relaxed/simple; bh=7x03GP5HY1uxXkss8Aja/ozWN2DFPzdhEztk8RTae5o=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=IU7/WFfgjtmr2Shda+AEZTNmttl5eZBLPsiW6vPDJLS/pJe3CNA7aEgj8e5mTZggKMkDUjoZ/nJkJdvzoTPqat98YlVAUPMZtk8cCOeDTTYbv+LNL3VedRLcgzrvPohNA3MQorIhWQudowRKDAgTsVAHD2ba29HtqoW/CHPwXNA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BCbVNamC; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BCbVNamC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BCBFA1F000E9; Wed, 27 May 2026 10:06:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779876372; bh=ED1wg3AcoDdFGNLgLheoY54/sZmjqAMcBOPJMgMobtc=; h=Date:Subject:To:References:From:In-Reply-To; b=BCbVNamCBtDDV+DyXMTTmxDEuzH9lwqSb0CMP3Y7MWsBH36Gs/G7XLQ9uEOcdQmij t/TBBohYWqdqmSeu2VqqEmA4RPu+6kC7TrdEdBbzfZoBdwHJn6ULvhaVY7OGlPYNbM D10Pa0z2GxWqwl53GKE6UXBrMDTW7vKJF8cnVjD5EzkTOnbX0+4xIp6i2Rmz6gdxY3 3YKuXnipdKKnr3wMfSQaF3y8mUzz+s99J5PQePKwy8uz15dL75m74PtnwbUfylfqdB Py1/i76/Xxv5R4HaYundlN4Mogm8d6AnmQ0QNzUWfjoITd8kUgBOORyR+S6+hqtMzo 9v9AeYoDwl2Rw== Message-ID: Date: Wed, 27 May 2026 12:06:08 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: revisiting alloc_pages_bulks semantics? Content-Language: en-US To: Christoph Hellwig , Andrew Morton , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Chuck Lever , "Matthew Wilcox (Oracle)" , linux-nfs@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260527071816.GA17632@lst.de> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260527071816.GA17632@lst.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/27/26 09:18, Christoph Hellwig wrote: > Hi all, > > I've been looking into using alloc_pages_bulks in a few places lately, > and have run into issues with the API. Here is my suggestions for how > to make this more useful, although only some of them are something > I'd feel comfortable to do myself: > > 1) early fail semantics > > alloc_pages_bulks can do partial allocations for some reasons, and > users usually have a fallback by either looping and calling it again > or falling back to single page allocations. This sucks! Why can't > we get our usual try as hard as you can semantics, requiring > GFP_NORETRY or similar to relax it? If we do that, do we keep the possibility of partial success, i.e. return how many were allocated? Seems wasteful to suceed N-1 and then throw all away, if the caller can use a fallback only for the last one. Do some callers need all-or-nothing semantics? Should a flag indicate which one to use? > 2) pre-zeroed page array > > There is one single user (svc_fill_pages in sunrpc) that relies on it. > For everyone else it creates extra burden and is very error prone > (speaking from experience). Sounds good to me. Will sunrpc be easy to convert, or should it be another flag to opt-in to the current behavior, that it would use? > 3) page instead of folio > > We're allocating folios, so we should have a folio API. Hm, folios initially started as "base or compound page" but then the semantics shifted and now they are also rmappable. See how folio_alloc_noprof() does page_rmappable_folio(). The differences might grow further with memdesc conversion I think. So do all the callers actually want folios? If not, we could have both alloc_pages_bulk() and folio_alloc_bulk()? > 4) > order 0 support > > The bulk allocator is limited to order 0 which limits it's usefulness > these days. It would be really helpful to do bulk allocations for > the pagecache or bounce buffering. Fine, with implications for the comment for 1)