From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794588719; b=44es0HoPvqChLl5jlWjKrl7Wo0GoMt0KnxgfViDvQ64kQ7B9L1BxbOWM9NL05n9dAHtr +w07GE7/ZcXLdOm3aLSaufNSPdOW0pyGQzx6jbVM6W7jtnT7y6blg4Kfn6Ciba8kMma5X /Kt1gpCeAwUG+cDvkUU4EraqBflLG4SYHVEdUdL8aKj5zbx2t34alkgAYCdAoTkN9//Ry uRAMfUEPuWukTDwCPxb30PuAMyFiVkgT/Vi2kpPciTnB9puhoUEJZSS9Kdo3+l4zaTkIQ Nl7OXOIvlND3htsyAFZQ7cY9/wS+0+k0j3Ah3qL55U7aVF0Nq70+SKi97F/Iu0gljOg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794588719; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:Content-Language:To:Cc:References:From:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=81quoW2k6mkSDxYpTE88hQE+QCAzt8EVUIrXpu/NyGI=; b=a2vMD3ho7uy7YWYPxoDcnTwFd0RayURBY2KS9Yl+1n9jQ9hqCKEm5X0XsBpclIWrG1RZ crij1EKMLu0he32Ztzhvrg3XbVuMSxIGh7v4evSYkmf3c0+x297I17wYmiVZBnITfBiEZ KEol3ACoTnVezaZJdY6R7CaeiDX1ur9MzNZOAl200pgrElYpV1wD3I+BnCDpUZJ0NanLf Pw0JYCBjV2bDiPkn7t/NvO1r8uQ9DFlPDSngSS26DkodyhXsUUtlq/RMHDv/Gmd8DlOn/ YD7C14qMKxgC0gh9AYoReLUc8FQmi/KW14mJH3W1MuD9JtpyY7moA9xt9yY9/H37mkw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=I9NBiz5E; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D7396606BCA9 for ; Fri, 13 Nov 2026 16:51:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=I9NBiz5E Received: by smtp.kernel.org (Postfix) with ESMTPSA id 894FB1F00926; Fri, 13 Nov 2026 16:51:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794588719; bh=81quoW2k6mkSDxYpTE88hQE+QCAzt8EVUIrXpu/NyGI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=I9NBiz5Ez+6wD7BoiSuyCOpwYabWH6Tc+DIbRwOfmaFkVxjlGU1HLSJnNaHmRRP80 4dSTNWtZcASxOZnARC9aL326QrmjIphlD5ktqfN6DleZsc71+FnVmXMzf9NMp4DxJf 5skgrXJToSDLBf/SRPOLahwKLBZpY412K7LqbeDaFOIMtDUYDxclaXX72Z7MFcHrEV HUBiNE3BOVxZXnhnbWngWcgVG9+1xSWPV1Q6rpPEwxObOBjyU9U0PQypDVY0tglQjH bPne5i8xJvyA4Rl+csRrHbyPIWyem3UxnqoZXudhJZU/ShslJw6AS7NCBcxJjxT+Hh IBpdh9cnB31Kg== Message-ID: <7e82bf2d-3a36-46d4-b63e-6b6720620380@kernel.org> Date: Fri, 13 Nov 2026 17:51:52 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] mm: page_alloc: add a watermark check that knows the migratetype Content-Language: en-US To: "Kiryl Shutsemau (Meta)" , Andrew Morton , Johannes Weiner , David Hildenbrand Cc: Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Zi Yan , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Qi Zheng , Shakeel Butt , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , Dev Jain , Harry Yoo , Usama Arif , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com References: <20261102093939.3340540-1-kas@kernel.org> <20261102093939.3340540-2-kas@kernel.org> 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: <20261102093939.3340540-2-kas@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/2/26 10:39, Kiryl Shutsemau (Meta) wrote: > The high-order check in __zone_watermark_ok() accepts a free page of any > migratetype. Under ALLOC_NOFRAGMENT, a request below pageblock_order can > only take a page of its own migratetype or claim a whole free block, so > the check can pass when the allocation cannot succeed. > > Telling those apart needs the request's migratetype, but not every check > wants them told apart. A check whether an allocation can be served now > has to count only the pages it can take. > > A check whether there is enough free memory counts every migratetype: > kswapd and kcompactd balancing a zone, order-0 thresholds, the > slowpath's forecast whether reclaim and compaction can still make > progress. Reclaim and compaction work across migratetypes to free whole > pageblocks. > > Move the body of __zone_watermark_ok() into __zone_watermark_ok_mt(), > which takes the migratetype as well, and make __zone_watermark_ok() a > wrapper around it for the second kind of check. These use the new > function: > > - the allocator fast path, zone_watermark_fast(); > - its recheck after node reclaim in get_page_from_freelist(); > - compaction's up-front check, compaction_suit_allocation_order(). > > Declare both in mm/internal.h: nothing outside mm uses them. Why not mm/page_alloc.h instead, now that it exists. > Nothing reads the migratetype yet: no functional change. > > Tested-by: Dev Jain > Signed-off-by: Kiryl Shutsemau (Meta) > --- > include/linux/mmzone.h | 3 --- > mm/compaction.c | 11 ++++++----- > mm/internal.h | 7 +++++++ > mm/page_alloc.c | 37 ++++++++++++++++++++++++++++--------- > 4 files changed, 41 insertions(+), 17 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index ecd1ebd49756..4d9347a399fa 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1637,9 +1637,6 @@ static inline unsigned long pgdat_end_pfn(pg_data_t *pgdat) > #include > > void build_all_zonelists(pg_data_t *pgdat); > -bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > - int highest_zoneidx, unsigned int alloc_flags, > - long free_pages); > bool zone_watermark_ok(struct zone *z, unsigned int order, > unsigned long mark, int highest_zoneidx, > unsigned int alloc_flags); > diff --git a/mm/compaction.c b/mm/compaction.c > index f1b2060eb201..6c553d0e90f8 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -2520,7 +2520,7 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order, > static enum compact_result > compaction_suit_allocation_order(struct zone *zone, unsigned int order, > int highest_zoneidx, unsigned int alloc_flags, > - bool async, bool kcompactd) > + int migratetype, bool async, bool kcompactd) > { > unsigned long free_pages; > unsigned long watermark; > @@ -2531,8 +2531,8 @@ compaction_suit_allocation_order(struct zone *zone, unsigned int order, > free_pages = zone_page_state(zone, NR_FREE_PAGES); > > watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK); > - if (__zone_watermark_ok(zone, order, watermark, highest_zoneidx, > - alloc_flags, free_pages)) > + if (__zone_watermark_ok_mt(zone, order, watermark, highest_zoneidx, > + alloc_flags, free_pages, migratetype)) > return COMPACT_SUCCESS; > > /* > @@ -2588,6 +2588,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) > ret = compaction_suit_allocation_order(cc->zone, cc->order, > cc->highest_zoneidx, > cc->alloc_flags, > + cc->migratetype, > cc->mode == MIGRATE_ASYNC, > !cc->direct_compaction); > if (ret != COMPACT_CONTINUE) > @@ -3073,7 +3074,7 @@ static bool kcompactd_node_suitable(pg_data_t *pgdat) > ret = compaction_suit_allocation_order(zone, > pgdat->kcompactd_max_order, > highest_zoneidx, alloc_flags, > - false, true); > + MIGRATE_MOVABLE, false, true); > if (ret == COMPACT_CONTINUE) > return true; > } > @@ -3116,7 +3117,7 @@ static void kcompactd_do_work(pg_data_t *pgdat) > > ret = compaction_suit_allocation_order(zone, > cc.order, zoneid, cc.alloc_flags, > - false, true); > + MIGRATE_MOVABLE, false, true); > if (ret != COMPACT_CONTINUE) > continue; > > diff --git a/mm/internal.h b/mm/internal.h > index 566cbd2dce48..8e58e2db5e09 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -726,6 +726,13 @@ extern int min_free_kbytes; > extern int defrag_mode; > > void setup_per_zone_wmarks(void); > +bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > + int highest_zoneidx, unsigned int alloc_flags, > + long free_pages); > +bool __zone_watermark_ok_mt(struct zone *z, unsigned int order, > + unsigned long mark, int highest_zoneidx, > + unsigned int alloc_flags, long free_pages, > + int migratetype); > void calculate_min_free_kbytes(void); > int __meminit init_per_zone_wmark_min(void); > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index a8cac5e01066..7730660bdd09 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3587,9 +3587,10 @@ static inline long __zone_watermark_unusable_free(struct zone *z, > * one free page of a suitable size. Checking now avoids taking the zone lock > * to check in the allocation paths if no pages are free. > */ > -bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > - int highest_zoneidx, unsigned int alloc_flags, > - long free_pages) > +bool __zone_watermark_ok_mt(struct zone *z, unsigned int order, > + unsigned long mark, int highest_zoneidx, > + unsigned int alloc_flags, long free_pages, > + int migratetype) > { > long min = mark; > int o; > @@ -3665,6 +3666,21 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > return false; > } > > +/* > + * For checks that are not about serving one allocation now: kswapd and > + * kcompactd balancing a zone, order-0 thresholds, forecasts whether > + * reclaim and compaction can still make progress. They count free pages > + * of every migratetype: reclaim and compaction work across migratetypes > + * to free whole pageblocks. > + */ What a slop comment, sigh. Can you rewrite it normally? > +bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > + int highest_zoneidx, unsigned int alloc_flags, > + long free_pages) > +{ > + return __zone_watermark_ok_mt(z, order, mark, highest_zoneidx, > + alloc_flags, free_pages, MIGRATE_MOVABLE); > +} > + > bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > int highest_zoneidx, unsigned int alloc_flags) > { > @@ -3697,8 +3713,8 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, > return true; > } > > - if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags, > - free_pages)) > + if (__zone_watermark_ok_mt(z, order, mark, highest_zoneidx, alloc_flags, > + free_pages, gfp_migratetype(gfp_mask))) > return true; > > /* > @@ -3710,8 +3726,9 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, > if (unlikely(!order && (alloc_flags & ALLOC_MIN_RESERVE) && z->watermark_boost > && ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) { > mark = z->_watermark[WMARK_MIN]; > - return __zone_watermark_ok(z, order, mark, highest_zoneidx, > - alloc_flags, free_pages); > + return __zone_watermark_ok_mt(z, order, mark, highest_zoneidx, > + alloc_flags, free_pages, > + gfp_migratetype(gfp_mask)); > } > > return false; > @@ -3923,8 +3940,10 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, > continue; > > /* did we reclaim enough */ > - if (!zone_watermark_ok(zone, order, mark, > - ac->highest_zoneidx, alloc_flags)) > + if (!__zone_watermark_ok_mt(zone, order, mark, > + ac->highest_zoneidx, alloc_flags, > + zone_page_state(zone, NR_FREE_PAGES), > + gfp_migratetype(gfp_mask))) > continue; > } >