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Fri, 27 Aug 2021 17:22:52 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap1.suse-dmz.suse.de with ESMTPSA id EiydLWwfKWE7FwAAGKfGzw (envelope-from ); Fri, 27 Aug 2021 17:22:52 +0000 Message-ID: Date: Fri, 27 Aug 2021 19:22:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.0.2 Content-Language: en-US To: Mike Kravetz , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Michal Hocko , Oscar Salvador , Zi Yan , Muchun Song , Naoya Horiguchi , David Rientjes , Hillf Danton References: <20210816224953.157796-1-mike.kravetz@oracle.com> <20210816162749.22b921a61156a091f3e1d14d@linux-foundation.org> <20210816184611.07b97f4c26b83090f5d48fab@linux-foundation.org> <10d86c18-f0cf-395f-4209-17ac71b9fc03@oracle.com> From: Vlastimil Babka Subject: Re: [PATCH RESEND 0/8] hugetlb: add demote/split page functionality In-Reply-To: <10d86c18-f0cf-395f-4209-17ac71b9fc03@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=DtGfX8D6; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b="X/2ZEkiH"; spf=pass (imf15.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 66755D00009A X-Stat-Signature: eqkti7mxq8tkd6teiyrg9ikfwp5s4yba X-HE-Tag: 1630084974-930297 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 8/25/21 00:08, Mike Kravetz wrote: > Add Vlastimil and Hillf, > > Well, I set up a test environment on a larger system to get some > numbers. My 'load' on the system was filling the page cache with > clean pages. The thought is that these pages could easily be reclaimed. > > When trying to get numbers I hit a hugetlb page allocation stall where > __alloc_pages(__GFP_RETRY_MAYFAIL, order 9) would stall forever (or at > least an hour). It was very much like the symptoms addressed here: > https://lore.kernel.org/linux-mm/20190806014744.15446-1-mike.kravetz@oracle.com/ > > This was on 5.14.0-rc6-next-20210820. > > I'll do some more digging as this appears to be some dark corner case of > reclaim and/or compaction. The 'good news' is that I can reproduce > this. Interesting, let's see if that's some kind of new regression. >> And the second problem would benefit from some words to help us >> understand how much real-world hurt this causes, and how frequently. >> And let's understand what the userspace workarounds look like, etc. > > The stall above was from doing a simple 'free 1GB page' followed by > 'allocate 512 MB pages' from userspace. Is the allocation different in any way than the usual hugepage allocation possible today? > Getting out another version of this series will be delayed, as I think > we need to address or understand this issue first. >