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charset=us-ascii Content-Disposition: inline In-Reply-To: <20230726104845.GS1901145@kernel.org> X-Rspamd-Queue-Id: ADE0920006 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 6n9g7qu5dae56qt7uoowr6dufwaj4y84 X-HE-Tag: 1690376277-814090 X-HE-Meta: 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 8FMQ6vVN I1Xh8niAIPFCVnu/vzKZCrLI1F3zg/CztRERfDslKdIkN3IaS1s05eY7QqA28/gFTI1xFi9XPkGhTcyuhyGDD0m8xgxNGKZNTNw0raI+wwXfLBC2rTnE3twG7sENamcJEqs+GXhii420NwAVbOeI1orKfK1T6XZgN5HjPbvr1bUZbRaNv4yGzk7hzEiCADjoULWRO 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 Wed 26-07-23 13:48:45, Mike Rapoport wrote: > On Wed, Jul 26, 2023 at 09:49:12AM +0200, Michal Hocko wrote: > > 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. > > What do you mean by "specific boot allocator behavior"? I mean that the expectation that the boot allocator starts from low addresses and functionality depending on that is too fragile. This has already caused some problems in the past IIRC. -- Michal Hocko SUSE Labs