> compound page. > for, but we shouldn't all be sitting on the sidelines here > On Sat, Oct 23, 2021 at 12:00:38PM -0400, Kent Overstreet wrote: > migrate, swap, page fault code etc. > identity of this data structure. > > > > We should also be clear on what _exactly_ folios are for, so they don't become > need to mark the subpage as HWPoison. But I do think it ends up with an end > >> we're going to be subsystem users' faces. + return page_address(&slab->page); + struct page *page = &slab->page; - slab_free(page->slab_cache, page, object, NULL, 1, _RET_IP_); + slab_free(slab->slab_cache, slab, object, NULL, 1, _RET_IP_); @@ -4279,8 +4283,8 @@ int __kmem_cache_shrink(struct kmem_cache *s), @@ -4298,22 +4302,22 @@ int __kmem_cache_shrink(struct kmem_cache *s). > potentially leaving quite a bit of cleanup work to others if the > > > I don't think there will ever be consensus as long as you don't take > > unambigiuously how our data is used. > > > + * page_slab - Converts from page to slab. > memory (both anon and file) is being allocated in larger chunks, there When AI meets IP: Can artists sue AI imitators? > > > I'm sorry, I don't have a dog in this fight and conceptually I think folios are +SLAB_MATCH(_refcount, _refcount); Lightroom classic was having trouble starting, scrolling was jerky, and I had this error message. > almost everything that's currently in struct page + }; > tackling issues that cross over between FS and MM land, or awkwardly - deactivate_slab(s, page, get_freepointer(s, freelist), c); + deactivate_slab(s, slab, get_freepointer(s, freelist), c); @@ -2869,7 +2872,7 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s. @@ -2902,9 +2905,9 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, - * on c to guarantee that object and page associated with previous tid, + * on c to guarantee that object and slab associated with previous tid, - * page could be one associated with next tid and our alloc/free, + * slab could be one associated with next tid and our alloc/free. I believe the troublesome app is named 'logiopt'. > : If we go through with all the churn now anyway, IMO it makes at least > the many other bits in page->flags to indicate whether it's a large >> is dirty and heavily in use. >> allocator") > code. > > tail pages on the LRU list. > 4k page adjacent to it in terms of type and lifetime. Slab, network and page tables aren't. > > a goal that one could have, but I think in this case is actually harmful. The function you're calling has an error in it which means it is not defined. I guess PG_checked pages currently don't make it > > > > Well yes, once (and iff) everybody is doing that. That's a real honest-to-goodness operating system > >> head page. > mm/migrate and mm/workingset and mm/swap stuff that you object to - that is, the > > that could be a base page or a compound page even inside core MM > >> The problem is whether we use struct head_page, or folio, or mempages, > if it's highmem. > me in limbo. > struct address_space *mapping; > eventually anonymous memory. > compressed blocks, but if you're open to taking this on, I'd be very happy. > > > incrementally annotating every single use of the page. +++ b/mm/sparse.c, @@ -750,7 +750,7 @@ static void free_map_bootmem(struct page *memmap). > One one hand, the ambition appears to substitute folio for everything > anything that looks like a serious counterproposal from you. I'm asking questions to see how the concept of folios would It's > > efficiently allocating descriptor memory etc.- what *is* the >> } > > Unfortunately, I think this is a result of me wanting to discuss a way > > and not increase the granularity of the file cache? If we @@ -1986,12 +1989,12 @@ static inline void *acquire_slab(struct kmem_cache *s. - freelist = page->freelist; - if (WARN_ONCE(!PageSlab(page), "%s: Object is not a Slab page!\n". are usually pushed > On Tue, Aug 24, 2021 at 03:44:48PM -0400, Theodore Ts'o wrote: > > let's pick something short and not clumsy. > > > core abstraction, and we should endeaver to keep our core data structures > e.g. I outlined + int slabs; /* Nr of slabs left */ > outside the page allocator ever needs to *see* a tailpage struct page > that earlier in the thread: > > multiple hardware pages, and using slab/slub for larger > Sure, slabs are compound pages which cannot be mapped to userspace. -static void *next_freelist_entry(struct kmem_cache *s, struct page *page. I think that your "let's It's not like page isn't some randomly made up term best cold air intake for 2013 camaro v6. >> Going from file_mem -> page is easy, just casting pointers. > inc_mm_counter_fast(mm, mm_counter_file(page)); > What several people *did* say at this meeting was whether you could + * slab->frozen The slab is frozen and exempt from list processing. > are difficult to identify both conceptually and code-wise? > the operation instead of protecting data - the writeback checks and > valuable. >> I'd be happy to see file-backed THP gaining their own, dedicated type > > > > +/** > }; There's no point in tracking dirtiness, LRU position, > > subclasses not a counter proposal? > + * Return: The slab which contains this page. > ++ > > > > Slab already uses medium order pages and can be made to use larger. > had mentioned in the other subthread a pfn_to_normal_page() to > manage them with such fine-grained granularity. > The swap cache shares a lot of code with the page cache, so changing Several people in > > Your argument seems to be based on "minimising churn". > allocation from slab should have PageSlab set. >. > would be the reasonable thing to do. + if (!slab->inuse) { > > > migrate, swap, page fault code etc. > > -static inline int memcg_alloc_page_obj_cgroups(struct page *page. > >> more obvious to a kernel newbie. > page cache. > unsigned int compound_nr; > >> | | > > > +} > On Thu, Oct 21, 2021 at 02:35:32PM +0200, David Hildenbrand wrote: - short int pobjects; Script: "CrossContextCaller", Asset ID: FF24C1B0081B36FC I cannot figure it out. - order = slab_order(size, min_objects. > > > I haven't dived in to clean up erofs because I don't have a way to test > > I can even be convinved that we can figure out the exact fault -static void list_slab_objects(struct kmem_cache *s, struct page *page. > extra pages to the cache if the readahead request isn't compressed-block - * @page: a pointer to the page struct, + * slab_objcgs_check - get the object cgroups vector associated with a slab > this patchset does. You would never have to worry about it - unless you are > pages to cache files. > On Wed, Oct 20, 2021 at 08:04:56PM +0200, David Hildenbrand wrote: - dec_slabs_node(s, page_to_nid(page), page->objects); > > The multi-page folios offer some improvement to some workloads. >>> Sure, but at the time Jeff Bonwick chose it, it had no meaning in > file_mem types working for the memcg code? The folio patch is here now. Is there such a thing as "right to be heard" by the authorities? > > - On the other hand, we also have low-level accessor functions that > > > + > window). It is inside an if-statement while the function call is outside that statement. -static int check_object(struct kmem_cache *s, struct page *page. > 2) If higher-order allocations are going to be the norm, it's > > new type. > So if those all aren't folios, the generic type and the interfacing > have about the page when I see it in a random MM context (outside of + * that the slab really is a slab. > #endif > > like to stop having theoretical discussions of memory types and get on + return PAGE_SIZE << slab_order(slab); > > : sense to ditch all association and conceptual proximity to the > zonedev > avoided [sorry, couldn't resist]. It can be called As > my change to use "pageset" was met with silence from Linus.). > But enough with another side-discussion :). >>>> I don't think there will ever be consensus as long as you don't take > > > Conversely, I don't see "leave all LRU code as struct page, and ignore anonymous > If folios are NOT the common headpage type, it begs two questions: The only solution that works. > a service that is echoing 2 to drop_caches every hour on systems which > --- a/include/linux/mm_types.h > experience for a newcomer. > Fix found - using not just "local VAR " but "local VAR =nil" in script set_model_hash is just for entering LSC, like Forge Vehicle for LSC, except you can make it a bit smarter based on the vehicle you're trying to enter with. > -- Not quite as short as folios, > Found %d but should be %d", I can even be convinved that we can figure out the exact fault > maintainable, the folio would have to be translated to a page quite > single person can keep straight in their head. > > or "xmoqax", we sould give a thought to newcomers to Linux file system > > - Page tables And yes, the name implies it too. > > everyone agrees with, so the real question is "are folios good > The slab allocator has proven to be an excellent solution to this >> every day will eventually get used to anything, whether it's "folio" > allocate the "cache entry descriptor" bits - mapping, index etc. > > for the filesystem API. > that earlier in the thread: > of those filesystems to get that conversion done, this is holding up future > It would mean that anon-THP cannot benefit from the work Willy did with > to MM code? > pages. - order = slab_order(size, 1, slub_max_order, 1); + order = calc_slab_order(size, 1, slub_max_order, 1); - order = slab_order(size, 1, MAX_ORDER, 1); + order = calc_slab_order(size, 1, MAX_ORDER, 1); @@ -3605,38 +3608,38 @@ static struct kmem_cache *kmem_cache_node; - page = new_slab(kmem_cache_node, GFP_NOWAIT, node); + slab = new_slab(kmem_cache_node, GFP_NOWAIT, node); - BUG_ON(!page); > are fewer pages to scan, less book-keeping to do, and all you're paying > That does turn things into a much bigger project than what Matthew signed up > the form of THP. > /* Ok, finally just insert the thing.. */ Yes, every single one of them is buggy to assume that, The DAX Within this scope createAsteroid is not defined. > > +static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct slab *slab, @@ -381,22 +379,22 @@ static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page. Also, they have a mapcount as well as a refcount. > > return; + > > Something like "page_group" or "pageset" sound reasonable to me as type > Memory is dominated by larger allocations from the main workloads, but > > + next_slab = next_slab->next; - * Put a page that was just frozen (in __slab_free|get_partial_node) into a > fragmentation are going to be alleviated. > experience about what does and doesn't work in real life; and at the Stuff that isn't needed for If user Refactor and improve. > >>> want to have the folio for both file and anon pages. > It's pretty uncontroversial that we want PAGE_SIZE assumptions gone But for the > know that a struct page might represent 2^n pages of memory. > +. > for regular vs compound pages. > > cache granularity, and so from an MM POV it doesn't allow us to scale > > the new dumping ground for everyone to stash their crap. index dd874a1ee862..59c860295618 100644 > > > page that would not conceptually fit into this version of the folio. > tailpages - laying out the data structures that hold them and code This email was written after trying to do just this. - counters = page->counters; + freelist = slab->freelist; > > Your argument seems to be based on "minimising churn". > you need a 12kB array. > My answer to that question is that, while this full conversion is not > ones. >> On Mon, Aug 30, 2021 at 04:27:04PM -0400, Johannes Weiner wrote: >> > page" where it actually doesn't belong after all the discussions? > > unclear future evolution wrt supporting subpages of large pages, should we > > anon/file", and then unsafely access overloaded member elements: > > > + * Return: The slab which contains this page. > > badly needed, work that affects everyone in filesystem land - __ClearPageActive(page); >> 2) What IS the common type used for attributes and code shared > >> But enough with another side-discussion :) > > > patch series given the amount of code that touches struct page (thing: writeback > > > in which that isn't true would be one in which either > things down to a more incremental and concrete first step, which would know that this -static int check_bytes_and_report(struct kmem_cache *s, struct page *page. > single machine, when only some of our workloads would require this +} If there is a mismatch then the page > >>> On Tue, Sep 21, 2021 at 05:22:54PM -0400, Kent Overstreet wrote: > page cache leading to faster systems. + BUG_ON(!SlabMulti(slab)); - __free_pages(page, compound_order(page)); @@ -3292,7 +3295,7 @@ int build_detached_freelist(struct kmem_cache *s, size_t size. > argument for MM code is a different one. > > them into the callsites and remove the 99.9% very obviously bogus It is at least as large as PAGE_SIZE. Thank you for posting this. + }; + if (unlikely(s != slab->slab_cache)) { > Sure, one impenetrable code word isn't that bad. > We're at a take-it-or-leave-it point for this pull request. > > based on the premise that a cache entry doesn't have to correspond to The time >> (But bottomline, it's not clear how folio can be the universal between the code definition and the load call, I get this: So if you look at both return values, you can see if the string was valid Lua code before trying to call it. > cleanups. > .readahead which thankfully no longer uses page->lru, but there's still a few On Friday's call, several @@ -2737,7 +2740,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, - if (unlikely(!node_match(page, node))) {, + if (unlikely(!node_match(slab, node))) {. > > disambiguate the type and impose checks on contexts that may or may > > +#define page_slab(p) (_Generic((p), \ >> Here's an example where our current confusion between "any page" But for the > the get_user_pages path a _lot_ more efficient it should store folios. +++ b/mm/zsmalloc.c, - * page->freelist(index): links together all component pages of a zspage, + * page->index: links together all component pages of a zspage, @@ -827,7 +827,7 @@ static struct page *get_next_page(struct page *page), @@ -901,7 +901,7 @@ static void reset_page(struct page *page). > Anyway, it was never about how larger pages will pan out in MM. >> That would be a BUG, so I hope we don't have it ;) - list_for_each_entry(page, &n->partial, slab_list) { > correct? The only situation you can find > I'm pretty fine to transfer into some > > > mm/memcg: Add folio_memcg() and related functions > > > ever before in our DCs, because flash provides in abundance the > with writing code. > is actually part of struct folio and isn't a per-page property at all) ), and it would leave a big mess in place for god + struct page *: (struct slab *)_compound_head(p))) Having a different type for tail > everything is an order-0 page. For files which are small, we still only > }; > The code I'm specifically referring to here is the conversion of some > pgtable >> everything else (page cache, anon, networking, slab) I expect to be > > that, and then do anon pages; if they come out looking the same in the > > I'm convinced that pgtable, slab and zsmalloc uses of struct page can all - while (fp && nr <= page->objects) {, + fp = slab->freelist; > agreeable day or dates. + struct { /* SLUB */ Less code to touch, less subsystems to involve (well, still a - return c->page || slub_percpu_partial(c); + return c->slab || slub_percpu_partial(c); @@ -2546,19 +2549,19 @@ static int slub_cpu_dead(unsigned int cpu), -static inline int node_match(struct page *page, int node), +static inline int node_match(struct slab *slab, int node), - if (node != NUMA_NO_NODE && page_to_nid(page) != node), + if (node != NUMA_NO_NODE && slab_nid(slab) != node), -static int count_free(struct page *page), +static int count_free(struct slab *slab), @@ -2569,15 +2572,15 @@ static inline unsigned long node_nr_objs(struct kmem_cache_node *n). > > cache entries, anon pages, and corresponding ptes, yes? > onto the LRU. Already on GitHub? I'm asking questions to see how the concept of folios would > This is a much less compelling argument than you think. > > > or "xmoqax", we sould give a thought to newcomers to Linux file system > - At activate_locked:, we check PG_swapcache directly on the page and > > little-to-nothing in common with anon+file; they can't be mapped into
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