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Thu, 27 Feb 2025 13:16:07 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id Ax5fAJdlwGeFXQAAD6G6ig (envelope-from ); Thu, 27 Feb 2025 13:16:07 +0000 Message-ID: <2ca6130a-3756-4480-8453-77c702d919da@suse.cz> Date: Thu, 27 Feb 2025 14:16:06 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] Revert "mm/page_alloc.c: don't show protection in zone's ->lowmem_reserve[] for empty zone" Content-Language: en-US To: Baoquan He Cc: Michal Hocko , Gabriel Krisman Bertazi , akpm@linux-foundation.org, linux-mm@kvack.org, Mel Gorman , Petr Tesarik References: <20250226032258.234099-1-krisman@suse.de> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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 BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 28AD11C0005 X-Stat-Signature: j7ekdy9jcge4wamydmc5gomw1yx4pefd X-Rspam-User: X-HE-Tag: 1740662169-305339 X-HE-Meta: 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 CExWGJbH PgPIg4idVe6yG6LHRJDCcztAG9wSKLFs6PPFklqfESx9ifIXroTv/XeaMMUsA1jxgFPsA6yMEHUchvltfyng9iHUSFzQHmEZLV++8VwWwHQr7B8FBfdtgEdJDLFSFdBjSkOtkh5cDlY9fyv4a6OBiQeT5JolybD7zxvjDdcS3KMPbxDVX0Jq/9rgsaTYz7Nte3S/Y1eV7WzEU00YMS85EmkshFtZVaLFmod6LmEIEk9x7AGJ2vJ+WoIxS4zO8Ff1RhfwKVCTloVVbZ7L9nAya5mGWrPVZrvordW4lrLMYjLHO8RGQj0DOKJwejsJPEkD4huvaOMF+/mjtk98e3KAE3GtIr63Yz4nAwHEt X-Bogosity: Ham, tests=bogofilter, spamicity=0.000043, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/27/25 11:24, Baoquan He wrote: >> I guess the issue doesn't happen in practice. In any case it's out of scope >> of the reverted commit and the revert. > It could happen on arm64 because arm64 only has ZONE_DMA by default and > its boundary is not fixed. I saw all zones are ZONE_DMA on arm64, I > guess it could be easier to see a arm64 system which only has ZONE_DMA > on node 0 and ZONE_NORMAL/MOVABLE on other nodes. Does it mean the ZONE_DMA is rather large then on arm64 then? In that case things probably works fine even if no protection is applied to it. The x86 ones are small and thus need(ed) it much more. So I don't think we proactively need to change anything unless there are known issues observed in practice. Another reason to avoid the effort is that hopefully we'll get rid of the DMA zones anyway? They don't work all that well anyway in modern times. Ccing Petr for awareness (due to his recent LPC talk about this topic)