lwn.git/arch/powerpc/mm/pgtable_64.c, branch v4.7.8

tree wide: get rid of __GFP_REPEAT for order-0 allocations part I

2016-06-25T00:23:52+00:00

This is the third version of the patchset previously sent [1]. I have basically only rebased it on top of 4.7-rc1 tree and dropped "dm: get rid of superfluous gfp flags" which went through dm tree. I am sending it now because it is tree wide and chances for conflicts are reduced considerably when we want to target rc2. I plan to send the next step and rename the flag and move to a better semantic later during this release cycle so we will have a new semantic ready for 4.8 merge window hopefully. Motivation: While working on something unrelated I've checked the current usage of __GFP_REPEAT in the tree. It seems that a majority of the usage is and always has been bogus because __GFP_REPEAT has always been about costly high order allocations while we are using it for order-0 or very small orders very often. It seems that a big pile of them is just a copy&paste when a code has been adopted from one arch to another. I think it makes some sense to get rid of them because they are just making the semantic more unclear. Please note that GFP_REPEAT is documented as * __GFP_REPEAT: Try hard to allocate the memory, but the allocation attempt * _might_ fail. This depends upon the particular VM implementation. while !costly requests have basically nofail semantic. So one could reasonably expect that order-0 request with __GFP_REPEAT will not loop for ever. This is not implemented right now though. I would like to move on with __GFP_REPEAT and define a better semantic for it. $ git grep __GFP_REPEAT origin/master | wc -l 111 $ git grep __GFP_REPEAT | wc -l 36 So we are down to the third after this patch series. The remaining places really seem to be relying on __GFP_REPEAT due to large allocation requests. This still needs some double checking which I will do later after all the simple ones are sorted out. I am touching a lot of arch specific code here and I hope I got it right but as a matter of fact I even didn't compile test for some archs as I do not have cross compiler for them. Patches should be quite trivial to review for stupid compile mistakes though. The tricky parts are usually hidden by macro definitions and thats where I would appreciate help from arch maintainers. [1] http://lkml.kernel.org/r/1461849846-27209-1-git-send-email-mhocko@kernel.org This patch (of 19): __GFP_REPEAT has a rather weak semantic but since it has been introduced around 2.6.12 it has been ignored for low order allocations. Yet we have the full kernel tree with its usage for apparently order-0 allocations. This is really confusing because __GFP_REPEAT is explicitly documented to allow allocation failures which is a weaker semantic than the current order-0 has (basically nofail). Let's simply drop __GFP_REPEAT from those places. This would allow to identify place which really need allocator to retry harder and formulate a more specific semantic for what the flag is supposed to do actually. Link: http://lkml.kernel.org/r/1464599699-30131-2-git-send-email-mhocko@kernel.org Signed-off-by: Michal Hocko Cc: "David S. Miller" Cc: "H. Peter Anvin" Cc: "James E.J. Bottomley" Cc: "Theodore Ts'o" Cc: Andy Lutomirski Cc: Benjamin Herrenschmidt Cc: Catalin Marinas Cc: Chen Liqin Cc: Chris Metcalf [for tile] Cc: Guan Xuetao Cc: Heiko Carstens Cc: Helge Deller Cc: Ingo Molnar Cc: Jan Kara Cc: John Crispin Cc: Lennox Wu Cc: Ley Foon Tan Cc: Martin Schwidefsky Cc: Matt Fleming Cc: Ralf Baechle Cc: Rich Felker Cc: Russell King Cc: Thomas Gleixner Cc: Vineet Gupta Cc: Will Deacon Cc: Yoshinori Sato Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

powerpc/mm: THP is only available on hash64 as of now

2016-05-11T11:53:56+00:00

Only code movement in this patch. No functionality change. Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc/mm: pte_frag abstraction

2016-05-11T11:53:54+00:00

In this patch we make the number of pte fragments per level 4 page table page a variable. Radix level 4 table size is 256 bytes and hence we can have 256 fragments per level 4 page. We don't update the fragment count in this patch. We need to do performance measurements to find the right value for fragment count. Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc/mm: vmalloc abstraction in preparation for radix

2016-05-11T11:53:53+00:00

The vmalloc range differs between hash and radix config. Hence make VMALLOC_START and related constants a variable which will be runtime initialized depending on whether hash or radix mode is active. Signed-off-by: Aneesh Kumar K.V [mpe: Fix missing init of ioremap_bot in pgtable_64.c for ppc64e] Signed-off-by: Michael Ellerman

powerpc/mm: Add radix pgalloc details

2016-05-11T11:53:51+00:00

Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc/mm: Make 4K and 64K use pte_t for pgtable_t

2016-05-11T11:53:51+00:00

This patch switches 4K Linux page size config to use pte_t * type instead of struct page * for pgtable_t. This simplifies the code a lot and helps in consolidating both 64K and 4K page allocator routines. The changes should not have any impact, because we already store physical address in the upper level page table tree and that implies we already do struct page * to physical address conversion. One change to note here is we move the pgtable_page_dtor() call for nohash to pte_fragment_free_mm(). The nohash related change is due to the related changes in pgtable_64.c. Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc/mm: Rename function to indicate we are allocating fragments

2016-05-11T11:53:50+00:00

Only code cleanup. No functionality change. Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc/mm: Make page table size a variable

2016-05-01T08:32:48+00:00

Radix and hash MMU models support different page table sizes. Make the #defines a variable so that existing code can work with variable sizes. Slice related code is only used by hash, so use hash constants there. We will replicate some of the boundary conditions with resepct to TASK_SIZE using radix values too. Right now we do boundary condition check using hash constants. Swapper pgdir size is initialized in asm code. We select the max pgd size to keep it simple. For now we select hash pgdir. When adding radix we will switch that to radix pgdir which is 64K. BUILD_BUG_ON check which is removed is already done in hugepage_init() using MAYBE_BUILD_BUG_ON(). Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc/mm/book3s: Rename hash specific PTE bits to carry H_ prefix

2016-05-01T08:32:43+00:00

This helps to make following hash only pte bits easier. We have kept _PAGE_CHG_MASK, _HPAGE_CHG_MASK and _PAGE_PROT_BITS as it is in this patch eventhough they use hash specific bits. Using them in radix as it is should be ok, because with radix we expect those bit positions to be zero. Only renames in this patch, no change in functionality. Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc/mm: Move hash and no hash code to separate files

2016-05-01T08:32:42+00:00

This patch reduces the number of #ifdefs in C code and will also help in adding radix changes later. Only code movement in this patch. Signed-off-by: Aneesh Kumar K.V [mpe: Propagate copyrights and update GPL text] Signed-off-by: Michael Ellerman