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bh=GONJa8tzUwqKA0Fz+wB3U1k6lRkAIjy3GSK0vW8uCcE=; b=joabLHJaqcBy5EOkcJ/+cXWbBd5JWYFFbiCuer3a/tc7fWHsOeV8TEvKSuciFuNDUBiJ6W K1lWHyWK28xzic4hIpByu5BwKQhKgITs56ZfTAF5OlP9c1v3b+qUR3Qqt++Fwd87LBqgjv DkBqFo4aQVUb02Kv1ckXdQQJHrgUOlM= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 0C0341341F; Wed, 26 Jul 2023 07:49:13 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id EPN5APnPwGTrMAAAMHmgww (envelope-from ); Wed, 26 Jul 2023 07:49:13 +0000 Date: Wed, 26 Jul 2023 09:49:12 +0200 From: Michal Hocko To: Mike Rapoport Cc: Ross Zwisler , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Mel Gorman , Vlastimil Babka , David Hildenbrand Subject: Re: collision between ZONE_MOVABLE and memblock allocations Message-ID: References: <20230718220106.GA3117638@google.com> <20230719054434.GG1901145@kernel.org> <20230719222604.GB3528218@google.com> <20230721112009.GP1901145@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230721112009.GP1901145@kernel.org> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: DB4DC4000D X-Stat-Signature: wj8cyzf67foy638mrqki8qwcksiz77oa X-Rspam-User: X-HE-Tag: 1690357754-402344 X-HE-Meta: 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 cERRn6h+ BeF9dMrv+YSnIUarme0buuXrTaB2Mx3uFHvSDnb6W22CEM12aOcFWWM1phO8iGjBnF6RCPLbzwdh4Drt4ZMlJwJUm75U4okvKMu5e1cqZDzmlfpdHAFIJDqe5J4NaLajoG2XSlKjOskY5xZ6YAy4xtUtAvnERStYl/GhhCf7aX2QAfenxmZLP9BmpYeKvxR2od9Fo 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 Fri 21-07-23 14:20:09, Mike Rapoport wrote: > On Wed, Jul 19, 2023 at 04:26:04PM -0600, Ross Zwisler wrote: > > On Wed, Jul 19, 2023 at 08:44:34AM +0300, Mike Rapoport wrote: > > > 3. Switch memblock to use bottom up allocations. Historically memblock > > > allocated memory from the top to avoid corrupting the kernel image and to > > > avoid exhausting precious ZONE_DMA. I believe we can use bottom-up > > > allocations with lower limit of memblock allocations set to 16M. > > > > > > With the hack below no memblock allocations will end up in ZONE_MOVABLE: > > > > Yep, I've confirmed that for my use cases at least this does the trick, thank > > you! I had thought about moving the memblock allocations, but had no idea it > > was (basically) already supported and thought it'd be much riskier than just > > adjusting where ZONE_MOVABLE lived. > > > > Is there a reason for this to not be a real option for users, maybe per a > > kernel config knob or something? I'm happy to explore other options in this > > thread, but this is doing the trick so far. > > I think we can make x86 always use bottom up. > > To do this properly we'd need to set lower limit for memblock allocations > to MAX_DMA32_PFN and allow fallback below it so that early allocations > won't eat memory from ZONE_DMA32. > > Aside from x86 boot being fragile in general I don't see why this wouldn't > work. This would add a very subtle depency of a functionality on the specific boot allocator behavior and that is bad for long term maintenance. -- Michal Hocko SUSE Labs