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Mon, 9 Dec 2024 19:01:06 +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 05qDFXI+V2dtVAAAD6G6ig (envelope-from ); Mon, 09 Dec 2024 19:01:06 +0000 Message-ID: Date: Mon, 9 Dec 2024 20:01:05 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/2] mm/page_alloc: conditionally split > pageblock_order pages in free_one_page() and move_freepages_block_isolate() Content-Language: en-US To: David Hildenbrand , linux-kernel@vger.kernel.org, Johannes Weiner Cc: linux-mm@kvack.org, Andrew Morton , Zi Yan , Yu Zhao References: <20241206095951.98007-1-david@redhat.com> <20241206095951.98007-2-david@redhat.com> 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: <20241206095951.98007-2-david@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5BDF2140040 X-Stat-Signature: xwmaki4eqx5e8s7q94fmcmiai4g5pfi4 X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1733770855-97832 X-HE-Meta: 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 MK/7qO4R IjLWzkIyAbRhMQwce2rDVes+bNBIVxLprC/Jg+EPYF7XCK0o0lNQT3iuNGYOBLS7vsTvE0cAnSM+I5y1EN/BWWHUlvsL5GAHOdz82vbPBvJLbjWRwTpvxd7X51yZSqm9AXVUwy9kE3kJ//eh07qQLec4Ym+Z8fLZaAg+S5Qq0LYXRt94qwtBn7lSQmGp+5sLTjYtWK7+VFvajH+WZc4JpVNuTng82yAKNXVrCmzzXf4GAfHW9LhMjj4+CSvsdg67v4e2P7VZoMiGvZ7bNgFOCOF0eMIa17DsKGCnwzJucX0EMjJ3irpLGz6GhUaNjBYm/KLMWmnDeleJ0UPf6vwLEVIwisd+nD1kA1/jH 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: List-Subscribe: List-Unsubscribe: On 12/6/24 10:59, David Hildenbrand wrote: > Let's special-case for the common scenarios that: > > (a) We are freeing pages <= pageblock_order > (b) We are freeing a page <= MAX_PAGE_ORDER and all pageblocks match > (especially, no mixture of isolated and non-isolated pageblocks) Well in many of those cases we could also just adjust the pageblocks... But perhaps they indeed shouldn't differ in the first place, unless there's an isolation attempt. > When we encounter a > MAX_PAGE_ORDER page, it can only come from > alloc_contig_range(), and we can process MAX_PAGE_ORDER chunks. > > When we encounter a >pageblock_order <= MAX_PAGE_ORDER page, > check whether all pageblocks match, and if so (common case), don't > split them up just for the buddy to merge them back. > > This makes sure that when we free MAX_PAGE_ORDER chunks to the buddy, > for example during system startups, memory onlining, or when isolating > consecutive pageblocks via alloc_contig_range()/memory offlining, that > we don't unnecessarily split up what we'll immediately merge again, > because the migratetypes match. > > Rename split_large_buddy() to __free_one_page_maybe_split(), to make it > clearer what's happening, and handle in it only natural buddy orders, > not the alloc_contig_range(__GFP_COMP) special case: handle that in > free_one_page() only. > > Signed-off-by: David Hildenbrand Acked-by: Vlastimil Babka +static void __free_one_page_maybe_split(struct zone *zone, struct page *page, > + unsigned long pfn, int order, fpi_t fpi_flags) > +{ > + const unsigned long end_pfn = pfn + (1 << order); > + int mt = get_pfnblock_migratetype(page, pfn); > + > + VM_WARN_ON_ONCE(order > MAX_PAGE_ORDER); > VM_WARN_ON_ONCE(!IS_ALIGNED(pfn, 1 << order)); > /* Caller removed page from freelist, buddy info cleared! */ > VM_WARN_ON_ONCE(PageBuddy(page)); > > - if (order > pageblock_order) > - order = pageblock_order; > - > - while (pfn != end) { > - int mt = get_pfnblock_migratetype(page, pfn); > + /* > + * With CONFIG_MEMORY_ISOLATION, we might be freeing MAX_ORDER_NR_PAGES > + * pages that cover pageblocks with different migratetypes; for example > + * only some migratetypes might be MIGRATE_ISOLATE. In that (unlikely) > + * case, fallback to freeing individual pageblocks so they get put > + * onto the right lists. > + */ > + if (!IS_ENABLED(CONFIG_MEMORY_ISOLATION) || > + likely(order <= pageblock_order) || > + pfnblock_migratetype_equal(pfn + pageblock_nr_pages, end_pfn, mt)) { > + __free_one_page(page, pfn, zone, order, mt, fpi_flags); > + return; > + } > > - __free_one_page(page, pfn, zone, order, mt, fpi); > - pfn += 1 << order; > + while (pfn != end_pfn) { > + mt = get_pfnblock_migratetype(page, pfn); > + __free_one_page(page, pfn, zone, pageblock_order, mt, fpi_flags); > + pfn += pageblock_nr_pages; > page = pfn_to_page(pfn); This predates your patch, but seems potentially dangerous to attempt pfn_to_page(end_pfn) with SPARSEMEM and no vmemmap and the end_pfn perhaps being just outside of the valid range? Should we change that? But seems this code was initially introduced as part of Johannes' migratetype hygiene series.