Messages in this thread | | | Date | Fri, 16 Apr 2021 09:25:56 +0200 | From | Oscar Salvador <> | Subject | Re: [PATCH v7 4/8] mm,memory_hotplug: Allocate memmap from the added memory range |
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On Thu, Apr 15, 2021 at 01:19:59PM +0200, David Hildenbrand wrote: > > Implementation wise we will reuse vmem_altmap infrastructure to override > > the default allocator used by __populate_section_memmap. > > Part of the implementation also relies on memory_block structure gaining > > a new field which specifies the number of vmemmap_pages at the beginning. > > This patch also introduces the following functions: > > > > - vmemmap_init_space: Initializes vmemmap pages by calling move_pfn_range_to_zone(), > > calls kasan_add_zero_shadow() or the vmemmap range and marks > > online as many sections as vmemmap pages fully span. > > - vmemmap_adjust_pages: Accounts/substract vmemmap_pages to node and zone > > present_pages > > - vmemmap_deinit_space: Undoes what vmemmap_init_space does. > > > > This is a bit asynchronous; and the function names are not really expressing what is being done :) I'll try to come up with better names below.
Yeah, was not happy either with the names but at that time I could not come up with anything better.
> It is worth mentioning that the real "mess" is that we want offline_pages() to properly handle zone->present_pages going to 0. Therefore, we want to manually mess with the present page count.
This should be explained by this:
"On offline, memory_block_offline() calls vmemmap_adjust_pages() prior to calling offline_pages(), because offline_pages() performs the tearing-down of kthreads and the rebuilding of the zonelists if the node/zone become empty."
Is not that clear?
> I suggest detecting the zone in here and just passing it down to online_pages().
Ok, makes sense.
> My take would be doing the present page adjustment after onlining succeeded: > > static int memory_block_online(struct memory_block *mem) > { > unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr); > unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block; > unsigned long nr_vmemmap_pages = mem->nr_vmemmap_pages; > struct zone *zone; > int ret; > > zone = mhp_get_target_zone(mem->nid, mem->online_type); > > if (nr_vmemmap_pages) { > ret = mhp_init_memmap_on_memory(start_pfn, nr_vmemmap_pages, zone); > if (ret) > return ret; > } > > ret = online_pages(start_pfn + nr_vmemmap_pages, nr_pages - nr_vmemmap_pages, zone); > if (ret) { > if (nr_vmemmap_pages) > mhp_deinit_memmap_on_memory(start_pfn, nr_vmemmap_pages); > return ret; > } > > /* > * Account once onlining succeeded. If the page was unpopulated, > * it is now already properly populated. > */ > if (nr_vmemmap_pages) > adjust_present_page_count(zone, nr_vmemmap_pages); > return 0; > } > > And the opposite: > > static int memory_block_offline(struct memory_block *mem) > { > unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr); > unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block; > unsigned long nr_vmemmap_pages = mem->nr_vmemmap_pages; > struct zone *zone; > int ret; > > zone = page_zone(pfn_to_page(start_pfn)); > > > /* > * Unaccount before offlining, such that unpopulated zones can > * properly be torn down in offline_pages(). > */ > if (nr_vmemmap_pages) > adjust_present_page_count(zone, -nr_vmemmap_pages); > > ret = offline_pages(start_pfn + nr_vmemmap_pages, nr_pages - nr_vmemmap_pages); > if (ret) { > if (nr_vmemmap_pages) > adjust_present_page_count(zone, +nr_vmemmap_pages); > return ret; > } > > if (nr_vmemmap_pages) > mhp_deinit_memmap_on_memory(start_pfn, nr_vmemmap_pages); > return 0; > } > > Having to do the present page adjustment manually is not completely nice, > but it's easier than manually having to mess with zones becomming populated/unpopulated > outside of online_pages()/offline_pages().
Ok, I like this, and the naming is much better. I will work on this shortly.
thanks David!
-- Oscar Salvador SUSE L3
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