Messages in this thread | | | Subject | Re: [PATCH 08/17] prmem: struct page: track vmap_area | From | Igor Stoppa <> | Date | Thu, 25 Oct 2018 02:01:02 +0300 |
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On 24/10/2018 06:12, Matthew Wilcox wrote: > On Wed, Oct 24, 2018 at 12:34:55AM +0300, Igor Stoppa wrote: >> The connection between each page and its vmap_area avoids more expensive >> searches through the btree of vmap_areas. > > Typo -- it's an rbtree.
ack
>> +++ b/include/linux/mm_types.h >> @@ -87,13 +87,24 @@ struct page { >> /* See page-flags.h for PAGE_MAPPING_FLAGS */ >> struct address_space *mapping; >> pgoff_t index; /* Our offset within mapping. */ >> - /** >> - * @private: Mapping-private opaque data. >> - * Usually used for buffer_heads if PagePrivate. >> - * Used for swp_entry_t if PageSwapCache. >> - * Indicates order in the buddy system if PageBuddy. >> - */ >> - unsigned long private; >> + union { >> + /** >> + * @private: Mapping-private opaque data. >> + * Usually used for buffer_heads if >> + * PagePrivate. >> + * Used for swp_entry_t if PageSwapCache. >> + * Indicates order in the buddy system if >> + * PageBuddy. >> + */ >> + unsigned long private; >> + /** >> + * @area: reference to the containing area >> + * For pages that are mapped into a virtually >> + * contiguous area, avoids performing a more >> + * expensive lookup. >> + */ >> + struct vmap_area *area; >> + }; > > Not like this. Make it part of a different struct in the existing union, > not a part of the pagecache struct. And there's no need to use ->private > explicitly.
Ok, I'll have a look at the googledoc you made
>> @@ -1747,6 +1750,10 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, >> if (!addr) >> return NULL; >> >> + va = __find_vmap_area((unsigned long)addr); >> + for (i = 0; i < va->vm->nr_pages; i++) >> + va->vm->pages[i]->area = va; > > I don't like it that you're calling this for _every_ vmalloc() caller > when most of them will never use this. Perhaps have page->va be initially > NULL and then cache the lookup in it when it's accessed for the first time. >
If __find_vmap_area() was part of the API, this loop could be left out from __vmalloc_node_range() and the user of the allocation could initialize the field, if needed.
What is the reason for keeping __find_vmap_area() private?
-- igor
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