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 DB65A3C4B89 for ; Mon, 29 Jun 2026 14:28:35 +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=1782743316; cv=none; b=d4V13ae31cuETogB/V9zjrx/Fk1TeHA5iETJ9yp40S8bNF/8UrFNLCGCG3Rxhtv/UKSGc4QsIka6VWw8sx1Tx48Zyz+um1wlcJvgnxSW2U7Lv6lWmpjRyRxw9xc60weBOolT7U7/dnMCYXJYohusnIlXlHIgeL9Zw0fWbNGzgkw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782743316; c=relaxed/simple; bh=NUsYY2akyTom4979P4+uivGlFsqODd20pq+vu1xnt3Q=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=IDx7gdbKbgo1vrJWHIqyGXRsw5DsLdS4Kcholwkk+5sQvR6ebM6jA3pY3N1HkLLr4n8bFScSmenkYJITRMA8UiukwlPkcIOe7ByvjBZDS10/l1ZbI8OzUEPPPr6SmQnRg7ivMM44TzHtLLBbN4pQeHe8NEYOZNxWUGYAOFEQl7M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=klYh+h+N; 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="klYh+h+N" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA1BE1F000E9; Mon, 29 Jun 2026 14:28:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782743315; bh=8JC0C0FVVaFQrsOmwXSu62JfKtEg4PNYqhPkdJ82cpY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=klYh+h+NCjpwB6o0nF2PE9VU7HROot7A/l/tv/vAa5i3AYwqhTAGp0lNFXv5ZnOls /24b2uxy4GIOG146+tDnU4pb6yZrqHKsVaiHla6LTVnjYhwPAoF1pKIIRR7x/wmnyt B9zGe02inWeG4xYGPgW0WbcIhm4zI4adsYmgUCqSs/40q8Xzl59W0RcYqVcPQo2Rvj /8K9mq25xFhAw0q2W3h3tqH9nO4E3ThAajOiOV1OOJHN85LW0i9qNmXpGo7XtTtGYe wHUbLcOD5rU5K1ewfN8O93ocsV+AU+43m//1LLmYPjumQlycrT2mCGcmIfPzSEb6Qj GcykTGdQkOUPA== Message-ID: <220774cb-ba5b-4a12-a649-955c83bfc704@kernel.org> Date: Mon, 29 Jun 2026 16:28:30 +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: [PATCH 1/4] mm/compaction: stop recording free page order in page->private Content-Language: en-US To: Zi Yan , Andrew Morton , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , David Hildenbrand , Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Mike Rapoport Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260628-keep-subpage-private-zero-at-free-v1-0-f4ce3930d10f@nvidia.com> <20260628-keep-subpage-private-zero-at-free-v1-1-f4ce3930d10f@nvidia.com> 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: <20260628-keep-subpage-private-zero-at-free-v1-1-f4ce3930d10f@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/29/26 04:56, Zi Yan wrote: > Commit 733aea0b3a7bb ("mm/compaction: add support for >0 order folio > memory compaction.") stores isolated free pages in an array indexed by free > page orders, it is no longer needed to store the order in each page's > ->private field. And there is no code using the stored order. Stop doing > that. Ah, great observation. Cool. > It also prepares for an upcoming change that ensures subpage->private is > zero at page free time and the removal of set_page_private(0) from > prep_compound_tail(). In alloc_contig_frozen_range_noprof(), > isolate_freepages_range() is used to grab free pages from buddy allocator > and it leaves the aforementioned page->private set until > either split_free_frozen_pages() or prep_new_page() is called. That > triggers the upcoming subpage->private nonzero check along once > set_page_private(0) is removed from prep_compound_tail(), which is called > via prep_new_page(). I'm not sure it needs to be said here (or in such detail?) > Signed-off-by: Zi Yan Reviewed-by: Vlastimil Babka (SUSE) > --- > mm/compaction.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index b776f35ad020..349838cc6c19 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -644,7 +644,6 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > isolated = __isolate_free_page(page, order); > if (!isolated) > break; > - set_page_private(page, order); > > nr_scanned += isolated - 1; > total_isolated += isolated; > @@ -1617,7 +1616,6 @@ static void fast_isolate_freepages(struct compact_control *cc) > /* Isolate the page if available */ > if (page) { > if (__isolate_free_page(page, order)) { > - set_page_private(page, order); > nr_isolated = 1 << order; > nr_scanned += nr_isolated - 1; > total_isolated += nr_isolated; > @@ -1846,7 +1844,6 @@ static struct folio *compaction_alloc_noprof(struct folio *src, unsigned long da > size >>= 1; > > list_add(&freepage[size].lru, &cc->freepages[start_order]); > - set_page_private(&freepage[size], start_order); > } > dst = (struct folio *)freepage; > >