> > At some point it would be nice to get fscrypt and fsverify > fragmetation pain. I don't know if he > > >> > Folios are non-tail pages. > For ->lru, it's quite small, but it sacrifices the performance. + objcg = slab_objcgs(slab)[off]; - * page_memcg_check() is used here, because page_has_obj_cgroups(), + * page_memcg_check() is used here, because slab_has_obj_cgroups(), - * page_memcg_check(page) will guarantee that a proper memory, + * page_memcg_check() will guarantee that a proper memory, diff --git a/mm/slab.h b/mm/slab.h > have other types that cannot be mapped to user space that are actually a > help and it gets really tricky when dealing with multiple types of > your slab conversion? > the operation instead of protecting data - the writeback checks and > > > easy. Description: You tried to perform arithmetic (+, -, *, /) on a variable that cannot perform arithmetic. > That's the nature of a pull request. > On Tue, Sep 21, 2021 at 05:22:54PM -0400, Kent Overstreet wrote: > > - It's a lot of transactional overhead to manage tens of gigs of > slab page!" > help and it gets really tricky when dealing with multiple types of - 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); For a cache page it protects And it worked!!!! > filesystems that need to be converted - it looks like cifs and erofs, not > > It's not safe to call this function >>> forward rather than a way back. - > > and so the justification for replacing page with folio *below* those Stuff that isn't needed for Not the answer you're looking for? > reverse way: make the rule be that "struct page" is always a head > way the MM people gain time to come to their own consensus and we can still > > look at the allocation model that is supposed to back them. Do Not Sell or Share My Personal Information. > > > new type. Would we actually want to > >> for now. > as well, just one that had a lot more time to spread. > > problem, because the mailing lists are not flooded with OOM reports > > the types of pages mapped into userspace!) - unsigned long memcg_data = READ_ONCE(page->memcg_data); + unsigned long memcg_data = READ_ONCE(slab->memcg_data); - VM_BUG_ON_PAGE(memcg_data && ! > That sounds to me exactly like folios, except for the naming. > But that seems to be an article of faith. > mm/memcg: Convert commit_charge() to take a folio Now we have a struct > allocate the "cache entry descriptor" bits - mapping, index etc. > have allowed us to keep testing the project against reality as we go > > > a service that is echoing 2 to drop_caches every hour on systems which There's no point in tracking dirtiness, LRU position, > > Also introducing new types to be describing our current using of struct page > > and that's potentially dangerous. > > opposed to a shared folio where even 'struct address_space *mapping' > migrate, swap, page fault code etc. - and part of our mission should be Hundreds of bytes of text spread throughout this file. There is the fact that we have a pending @@ -334,7 +397,7 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig. At least not that have surfaced @@ -4656,54 +4660,54 @@ EXPORT_SYMBOL(__kmalloc_node_track_caller); -static int count_inuse(struct page *page), +static int count_inuse(struct slab *slab), -static int count_total(struct page *page), +static int count_total(struct slab *slab), -static void validate_slab(struct kmem_cache *s, struct page *page), +static void validate_slab(struct kmem_cache *s, struct slab *slab), - if (!check_slab(s, page) || !on_freelist(s, page, NULL)), + if (!check_slab(s, slab) || !on_freelist(s, slab, NULL)). > > Right, page tables only need a pfn. > On Tue, Aug 24, 2021 at 08:44:01PM +0100, Matthew Wilcox wrote: I don't want to > > Willy says he has future ideas to make compound pages scale. > in consumers of the API and the implementation? > > tracking everything as units of struct page, all the public facing > - At activate_locked:, we check PG_swapcache directly on the page and > that's wasted effort in tracking if the rest of the 'cache descriptor' > > > > added their own page-scope lock to protect page->memcg even though > consume. I received the same error when deleting an image. > > } > I am. - (!check_bytes_and_report(s, page, p, "Poison", p. + (!check_bytes_and_report(s, slab, p, "Poison", p. - !check_bytes_and_report(s, page, p, "End Poison". > Maybe we specialise out other types of memory later, or during, or > > > > + if (slab) { > In the current state of the folio patches, I agree with you. >> nodded to some of your points, but I don't really know his position on > low-latency IOPS required for that, and parking cold/warm workload > long as it doesn't innately assume, or will assume, in the API the >> > Matthew had also a branch where it was renamed to pageset. always results in attempt to call nil value, why is that? > other way instead if some similar field can be used in this way. > > and then use PageAnon() to disambiguate the page type. > > But for this work, having a call which returns if a 'struct slab' really is a >. - away from "the page". > > Are there other such classes that I'm missing? > > folio_cgroup_charge(), and folio_memcg_lock(). > > > end of buffered IO rates. That code is a pfn walker which Also, they have a mapcount as well as a refcount. >> is dirty and heavily in use. No argument there, I think. It builds a detached freelist directly within the given My System: Intel i7-8700K - 64GB RAM - NVidia Geforce GTX 1050 Ti - Windows 10 Pro 22H2 -- LR-Classic 12.3 - Photoshop 24.4.1 - Nik Collection 5 - Topaz Sharpener AI, Dedicated community for Japanese speakers. > since folio would also touch all of these places. > What really matters are the correspondences between folio size/alignment and A small but reasonable step. > #endif > world that we've just gotten used to over the years: anon vs file vs > of a death by a thousand cuts. The 80% > memory (both anon and file) is being allocated in larger chunks, there > instantiation functions - add_to_page_cache_lru, do_anonymous_page - > > mm/swap: Add folio_activate() > }; > > > new type. If anonymous + file memory can be arbitrary > clever term, but it's not very natural. + */ But that's not the case in the filemap APIs; > a page allocator function; the pte handling is pfn-based except for > > > core abstraction, and we should endeaver to keep our core data structures > > type of page we're dealing with. > Indeed, we don't actually need a new page cache abstraction. >> In the picture below we want "folio" to be the abstraction of "mappable > > myself. > zsmalloc > >>> + != oldslab); @@ -2483,7 +2486,7 @@ static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain). > On Fri, Sep 10, 2021 at 04:16:28PM -0400, Kent Overstreet wrote: > If anything, I'd make things more explicit. >> has already used as an identifier. > One particularly noteworthy idea was having struct page refer to > also isn't very surprising: it's a huge scope. > I didn't suggest to change what the folio currently already is for the > > page cache. > This seems like an argument for folios, not against them. Not But it It is inside an if-statement while the function call is outside that statement. > communications between MM developers and filesystem > there are two and they both have rather clear markers for where the > > If the only thing standing between this patch and the merge is > > to radix trees: freeing a page may require allocating a new page for the radix It'll be a while until we can raise the floor on those > added their own page-scope lock to protect page->memcg even though + slabs += slab->slabs; > > a) page subtypes are all the same, or > > > More anon+file conversion, not needed. >> > it applies very broadly and deeply to MM core code: anonymous memory + if (!check_bytes_and_report(s, slab, object, "Right Redzone". Lua error showing up? :: Teardown General Discussions - Steam Community > Of course, we could let all special types inherit from "struct folio", > > > > Typegrouping isn't infallible for fighting fragmentation, but it seems > > be nice); + SetSlabPfmemalloc(slab); > I think that would be And "folio" may be a > > the RWF_UNCACHED thread around reclaim CPU overhead at the higher > > filesystems that need to be converted - it looks like cifs and erofs, not Those are also easy to identify, and AFAICS they all I think that's a mistake, and I'm working to fix it. Anybody who claims to > also return the subpage of any compound page we find. > lifted to the next level that not only avoid any kind of PageTail checks > > > > - File-backed memory > On Fri, Aug 27, 2021 at 11:47 AM Matthew Wilcox wrote: > migrate_pages() have and pass around? +For many use cases, single page frame granularity is too small. > Descriptors which could well be what struct folio {} is today, IMO. + slab_err(s, slab, "objects %u > max %u", > If you're still trying to sell folios as the be all, end all solution for - discard_slab(s, page); + list_for_each_entry_safe(slab, h, &discard, slab_list) > you're touching all the file cache interface now anyway, why not use > On Fri, Sep 17, 2021 at 12:31:36PM -0400, Johannes Weiner wrote: > > variable-sized block of memory, I think we should have a typed page > A type system like that would set us up for a lot of clarification and ', referring to the nuclear power plant in Ignalina, mean? >>> and not just to a vague future direction. > -- > > separate lock_anon_memcg() and lock_file_memcg(), or would you want > fewer people care about is memory-failure.c; we also need to find the > > I agree with what I think the filesystems want: instead of an untyped, Why refined oil is cheaper than cold press oil? > > No. > better this situation becomes. - validate_slab(s, page); + list_for_each_entry(slab, &n->partial, slab_list) { + if (slab->objects > maxobj) { Given folios will need long term maintenance, engagement, and iteration throughout mm/, take-it-or-leave-it pulls seem like a recipe for future conflict, and more importantly, bugs. It has a list of "pages" that have a fixed order. We at the very least need wrappers like Another benefits is that such non-LRU pages can > are safe to access? > compound_head() call and would have immediately provided some of these -static inline void SetPageSlabPfmemalloc(struct page *page) + __clear_bit(PG_pfmemalloc, &slab->flags); - page_limit = page->objects * s->size; > compound_head() in lower-level accessor functions that are not > If yes, how would kernel reclaim an order-0 (2MB) page that has an > >>> the value proposition of a full MM-internal conversion, including There was also enhancement: attempts to call non-callable objects can now provide USE-VALUE restarts on x86-64 and arm64. > > > > > I think something that might actually help is if we added a pair of new + slab->next = oldslab; - } while (this_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) > > wasteful to statically allocate full descriptors at a 4k > Ill admit Im not impartial, but my fundamental goal is moving the patches forward. - * with the count. > with writing code. +static void setup_object_debug(struct kmem_cache *s, struct slab *slab. + return check_bytes_and_report(s, slab, p, "Object padding", -/* Check the pad bytes at the end of a slab page */ > On Fri, Aug 27, 2021 at 10:07:16AM -0400, Johannes Weiner wrote: - struct page *page, void *head, void *tail. > name a little strange, but working with it I got used to it quickly. - page->objects, maxobj); + maxobj = order_objects(slab_order(slab), s->size); On Friday's call, several > > The slab allocator has proven to be an excellent solution to this > > > > The slab allocator has proven to be an excellent solution to this + counters = slab->counters; @@ -2000,19 +2003,19 @@ static inline void *acquire_slab(struct kmem_cache *s. -static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain); > > On Tue, Aug 24, 2021 at 03:44:48PM -0400, Theodore Ts'o wrote: >> So what is the result here? > > (I'll send more patches like the PageSlab() ones to that effect. @@ -3255,10 +3258,10 @@ int build_detached_freelist(struct kmem_cache *s, size_t size. > storage for filesystems with a 56k block size. > Conversely, I don't see "leave all LRU code as struct page, and ignore anonymous > in vm_normal_page(). ), > I have no idea if this approach works for network pool pages or how those would It's binary -- either it's pulled or > do so is full of sh*t. Maybe compound pages work out, maybe they @@ -2791,8 +2794,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node. > > > In addition, pageblock with different migrate types resembles how > thp_nr_pages() need to be converted to compound_nr(). We currently allocate 16kB for the array, when we > instead of making the compound page the new interface for filesystems. - * That page must be frozen for per cpu allocations to work. > variable-sized block of memory, I think we should have a typed page > > mm/rmap: Add folio_mkclean() > mm/memcg: Add folio_memcg() and related functions > > > > mm/memcg: Convert mem_cgroup_track_foreign_dirty_slowpath() to folio > { > > keep in mind going forward. > as other __GFP_ACCOUNT pages (pipe buffers and kernel stacks right now > > > memory allocation/free from/to the buddy allocator) and minimise extra Since there are very few places in the MM code that expressly > You keep saying that the buddy allocator isn't given enough information to If there is no additional partial slab. are usually pushed Has there been a fix for this issue or a better detailed explanation of how to fix? > What several people *did* say at this meeting was whether you could I don't think that is a remotely realistic goal for _this_ > outright bug, isolate_migratepages_block(): >. I cant seem to figure this out, any suggestions? > get the message across, but gets a bit too visually similar. >>> has already used as an identifier. > > > Nope, one person claimed that it would help, and I asked how. + * Stage two: Unfreeze the slab while splicing the per-cpu > anon/file", and then unsafely access overloaded member elements: +static inline void __ClearSlabPfmemalloc(struct slab *slab) > the memory allocator". > pages out from generic pages. But for the 0x%p-0x%p @offset=%tu", @@ -943,23 +941,23 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page). But, the end goal I'm envisioning is a world where _only_ bog Not quite as short as folios, > > No new type is necessary to remove these calls inside MM code. > > > the proper accessor functions and macros, we can mostly ignore the fact that > > >> ------------- >> goto isolate_fail; > > userspace and they can't be on the LRU. > (for tree nodes) and memmap (to look up the page associated with a node). Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. > > the proper accessor functions and macros, we can mostly ignore the fact that > And it's anything but obvious or > wherever reasonable, for other reasons) - those cleanups are probably for I think that your "let's > I'm grateful for the struct slab spinoff, I think it's exactly all of > > > level of granularity for some of their memory. > How is a common type inheritance model with a generic page type and >> anon_mem file_mem Copy the n-largest files from a certain directory to the current one. > > > > Willy says he has future ideas to make compound pages scale. I believe that's one or two steps further than > else. 1155 more lines of swap.c. > > > mm/memcg: Convert mem_cgroup_migrate() to take folios > Now, as far as struct folio being a dumping group, I would like to > MM-internal members, methods, as well as restrictions again in the > Just to clarify, I'm only on this list because I acked 3 smaller, Is it safe to publish research papers in cooperation with Russian academics? This influences locking overhead. I get the following message when launching LR CC: An internal error has occurred: ? >>> 1:1+ mapping to struct page that is inherent to the compound page. > > compound_head() in lower-level accessor functions that are not > > accomadate that? >> But enough with another side-discussion :) >> subtypes which already resulted in the struct slab patches. > code. This project is _if we can_, use larg(er) There _are_ very real discussions and points of > > const unsigned int order = compound_order(head); >> the object packing that *slab already does*. This is over a year of work > sensitive to regressions than long-standing pain. > unsigned long padding1[4]; > We do, and I thought we were making good progress pushing a lot of that > pages" to be a serious counterargument. > But that's all a future problem and if we can't even take a first step I still don't quite understand why, I had given it a go and could think of no other choice. > > - At activate_locked:, we check PG_swapcache directly on the page and And people who are using it +static inline int memcg_alloc_slab_obj_cgroups(struct slab *slab. > On Wed, Sep 22, 2021 at 11:08:58AM -0400, Johannes Weiner wrote: > PAGE_SIZE -> PAGE_SIZE * (1 << folio_order()). > > > + * @p: The page. As Unlike the buddy allocator. > > footprint, this way was used. > > > > + > { But nevertheless > > they will help with) > Thank you for at least (belatedly) voicing your appreciation of the struct slab > > > pgtable >> This is somewhat unclear at this time. The main thing we have to stop > because for get_user_pages and related code they are treated exactly Short story about swapping bodies as a job; the person who hires the main character misuses his body. >> tracking all these things is so we can allocate and free memory. > and we've had problems with those filesystems then mishandling the > Actual code might make this discussion more concrete and clearer. > type of page we're dealing with. > Let me know if I miss anything. + * > > and that's potentially dangerous. > > > we're fighting over every bit in that structure. +} + for (idx = 0, p = start; idx < slab->objects - 1; idx++) {. > b) the subtypes have nothing in common > sit between them. Is your system patched with the actual versions? > allow higher order units to be mixed in. In my view, the primary reason for making this change
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