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[2603:7000:c01:2716:3012:16a2:6bc2:2937]) by smtp.gmail.com with ESMTPSA id g28-20020a0caadc000000b0064d6a81e4d4sm896666qvb.113.2023.09.18.07.09.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Sep 2023 07:09:01 -0700 (PDT) Date: Mon, 18 Sep 2023 10:09:00 -0400 From: Johannes Weiner To: Vlastimil Babka Cc: Mike Kravetz , Andrew Morton , Mel Gorman , Miaohe Lin , Kefeng Wang , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V2 0/6] mm: page_alloc: freelist migratetype hygiene Message-ID: <20230918140900.GA16104@cmpxchg.org> References: <20230911195023.247694-1-hannes@cmpxchg.org> <20230914235238.GB129171@monkey> <20230915141610.GA104956@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 0273E2003A X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ijznyr9778w7uxoh6nxnnd1sgig5b94a X-HE-Tag: 1695046142-688346 X-HE-Meta: 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 3QYwamCc /pbP5VnbzB3SEtd59FO/4zUffQwdIiWnPaXh/P7R9VU3lTrbIICEA2dxf33fDPXk9PBCPLF+BaFG9LyNwcgADoTEXfZuxnk2+H7+c1mENOfiOB+AU9Jz3PB3EECTXFQuRef6CkOdLGNo2D7uZ34Gq0VehMtrknGacaB4un/Gjow4hFdjvPJeOrrkUBz42OuH/bcB9Sl2Ja9jmaYARR5wevWS7NrMjpcMLWxumWp97Wd20OCzHoofHvcWg2zdhmcGI+GccVtdLYIMIeDWCzjCZ2iErcBUUXM6StMu39zW5LF+RRgiKi0iqmMxY3/oGI1edbGVnzWKJlk7VOZhOaSreTgFtRRF2NvVrEltb+iETUES+A5oviM48aZUuaHhnHK1g2wi4nbWYtHiH/n49BoIfsriUlHnXF6vB3XYUYMS/NjmJgxjxCqAg52QcAI3wRbGViWJn 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: On Mon, Sep 18, 2023 at 09:07:53AM +0200, Vlastimil Babka wrote: > On 9/15/23 16:16, Johannes Weiner wrote: > > On Thu, Sep 14, 2023 at 04:52:38PM -0700, Mike Kravetz wrote: > >> In next-20230913, I started hitting the following BUG. Seems related > >> to this series. And, if series is reverted I do not see the BUG. > >> > >> I can easily reproduce on a small 16G VM. kernel command line contains > >> "hugetlb_free_vmemmap=on hugetlb_cma=4G". Then run the script, > >> while true; do > >> echo 4 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages > >> echo 4 > /sys/kernel/mm/hugepages/hugepages-1048576kB/demote > >> echo 0 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages > >> done > >> > >> For the BUG below I believe it was the first (or second) 1G page creation from > >> CMA that triggered: cma_alloc of 1G. > >> > >> Sorry, have not looked deeper into the issue. > > > > Thanks for the report, and sorry about the breakage! > > > > I was scratching my head at this: > > > > /* MIGRATE_ISOLATE page should not go to pcplists */ > > VM_BUG_ON_PAGE(is_migrate_isolate(mt), page); > > > > because there is nothing in page isolation that prevents setting > > MIGRATE_ISOLATE on something that's on the pcplist already. So why > > didn't this trigger before already? > > > > Then it clicked: it used to only check the *pcpmigratetype* determined > > by free_unref_page(), which of course mustn't be MIGRATE_ISOLATE. > > > > Pages that get isolated while *already* on the pcplist are fine, and > > are handled properly: > > > > mt = get_pcppage_migratetype(page); > > > > /* MIGRATE_ISOLATE page should not go to pcplists */ > > VM_BUG_ON_PAGE(is_migrate_isolate(mt), page); > > > > /* Pageblock could have been isolated meanwhile */ > > if (unlikely(isolated_pageblocks)) > > mt = get_pageblock_migratetype(page); > > > > So this was purely a sanity check against the pcpmigratetype cache > > operations. With that gone, we can remove it. > > Agreed, I assume you'll fold it in 1/6 in v3. Yes, will do.