linux/arch/microblaze/include/asm/page.h
David Hildenbrand 8e38607aa4 treewide: provide a generic clear_user_page() variant
Patch series "mm: folio_zero_user: clear page ranges", v11.

This series adds clearing of contiguous page ranges for hugepages.

The series improves on the current discontiguous clearing approach in two
ways:

  - clear pages in a contiguous fashion.
  - use batched clearing via clear_pages() wherever exposed.

The first is useful because it allows us to make much better use of
hardware prefetchers.

The second, enables advertising the real extent to the processor.  Where
specific instructions support it (ex.  string instructions on x86; "mops"
on arm64 etc), a processor can optimize based on this because, instead of
seeing a sequence of 8-byte stores, or a sequence of 4KB pages, it sees a
larger unit being operated on.

For instance, AMD Zen uarchs (for extents larger than LLC-size) switch to
a mode where they start eliding cacheline allocation.  This is helpful not
just because it results in higher bandwidth, but also because now the
cache is not evicting useful cachelines and replacing them with zeroes.

Demand faulting a 64GB region shows performance improvement:

 $ perf bench mem mmap -p $pg-sz -f demand -s 64GB -l 5

                       baseline              +series
                   (GBps +- %stdev)      (GBps +- %stdev)

   pg-sz=2MB       11.76 +- 1.10%        25.34 +- 1.18% [*]   +115.47%  	preempt=*

   pg-sz=1GB       24.85 +- 2.41%        39.22 +- 2.32%       + 57.82%  	preempt=none|voluntary
   pg-sz=1GB         (similar)           52.73 +- 0.20% [#]   +112.19%  	preempt=full|lazy

 [*] This improvement is because switching to sequential clearing
  allows the hardware prefetchers to do a much better job.

 [#] For pg-sz=1GB a large part of the improvement is because of the
  cacheline elision mentioned above. preempt=full|lazy improves upon
  that because, not needing explicit invocations of cond_resched() to
  ensure reasonable preemption latency, it can clear the full extent
  as a single unit. In comparison the maximum extent used for
  preempt=none|voluntary is PROCESS_PAGES_NON_PREEMPT_BATCH (32MB).

  When provided the full extent the processor forgoes allocating
  cachelines on this path almost entirely.

  (The hope is that eventually, in the fullness of time, the lazy
   preemption model will be able to do the same job that none or
   voluntary models are used for, allowing us to do away with
   cond_resched().)

Raghavendra also tested previous version of the series on AMD Genoa and
sees similar improvement [1] with preempt=lazy.

  $ perf bench mem map -p $page-size -f populate -s 64GB -l 10

                    base               patched              change
   pg-sz=2MB       12.731939 GB/sec    26.304263 GB/sec     106.6%
   pg-sz=1GB       26.232423 GB/sec    61.174836 GB/sec     133.2%


This patch (of 8):

Let's drop all variants that effectively map to clear_page() and provide
it in a generic variant instead.

We'll use the macro clear_user_page to indicate whether an architecture
provides it's own variant.

Also, clear_user_page() is only called from the generic variant of
clear_user_highpage(), so define it only if the architecture does not
provide a clear_user_highpage().  And, for simplicity define it in
linux/highmem.h.

Note that for parisc, clear_page() and clear_user_page() map to
clear_page_asm(), so we can just get rid of the custom clear_user_page()
implementation.  There is a clear_user_page_asm() function on parisc, that
seems to be unused.  Not sure what's up with that.

Link: https://lkml.kernel.org/r/20260107072009.1615991-1-ankur.a.arora@oracle.com
Link: https://lkml.kernel.org/r/20260107072009.1615991-2-ankur.a.arora@oracle.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Co-developed-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ankur Arora <ankur.a.arora@oracle.com>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Konrad Rzessutek Wilk <konrad.wilk@oracle.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Li Zhe <lizhe.67@bytedance.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@amd.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2026-01-20 19:24:39 -08:00

141 lines
3.6 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
/*
* VM ops
*
* Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
* Copyright (C) 2008-2009 PetaLogix
* Copyright (C) 2006 Atmark Techno, Inc.
* Changes for MMU support:
* Copyright (C) 2007 Xilinx, Inc. All rights reserved.
*/
#ifndef _ASM_MICROBLAZE_PAGE_H
#define _ASM_MICROBLAZE_PAGE_H
#include <linux/pfn.h>
#include <asm/setup.h>
#include <asm/asm-compat.h>
#include <linux/const.h>
#ifdef __KERNEL__
#include <vdso/page.h>
#define LOAD_OFFSET ASM_CONST((CONFIG_KERNEL_START-CONFIG_KERNEL_BASE_ADDR))
#define PTE_SHIFT (PAGE_SHIFT - 2) /* 1024 ptes per page */
#ifndef __ASSEMBLER__
/*
* PAGE_OFFSET -- the first address of the first page of memory. With MMU
* it is set to the kernel start address (aligned on a page boundary).
*
* CONFIG_KERNEL_START is defined in arch/microblaze/config.in and used
* in arch/microblaze/Makefile.
*/
#define PAGE_OFFSET CONFIG_KERNEL_START
/*
* The basic type of a PTE - 32 bit physical addressing.
*/
typedef unsigned long pte_basic_t;
#define PTE_FMT "%.8lx"
# define copy_page(to, from) memcpy((to), (from), PAGE_SIZE)
# define clear_page(pgaddr) memset((pgaddr), 0, PAGE_SIZE)
# define copy_user_page(vto, vfrom, vaddr, topg) \
memcpy((vto), (vfrom), PAGE_SIZE)
/*
* These are used to make use of C type-checking..
*/
typedef struct page *pgtable_t;
typedef struct { unsigned long pte; } pte_t;
typedef struct { unsigned long pgprot; } pgprot_t;
/* FIXME this can depend on linux kernel version */
typedef struct { unsigned long pgd; } pgd_t;
# define pte_val(x) ((x).pte)
# define pgprot_val(x) ((x).pgprot)
# define pgd_val(x) ((x).pgd)
# define __pte(x) ((pte_t) { (x) })
# define __pgd(x) ((pgd_t) { (x) })
# define __pgprot(x) ((pgprot_t) { (x) })
/**
* Conversions for virtual address, physical address, pfn, and struct
* page are defined in the following files.
*
* virt -+
* | asm-microblaze/page.h
* phys -+
* | linux/pfn.h
* pfn -+
* | asm-generic/memory_model.h
* page -+
*
*/
extern unsigned long max_low_pfn;
extern unsigned long min_low_pfn;
extern unsigned long max_pfn;
extern unsigned long memory_start;
extern unsigned long memory_size;
extern unsigned long lowmem_size;
extern unsigned long kernel_tlb;
extern int page_is_ram(unsigned long pfn);
# define phys_to_pfn(phys) (PFN_DOWN(phys))
# define pfn_to_phys(pfn) (PFN_PHYS(pfn))
# define virt_to_page(kaddr) (pfn_to_page(__pa(kaddr) >> PAGE_SHIFT))
# define page_to_virt(page) __va(page_to_pfn(page) << PAGE_SHIFT)
# define ARCH_PFN_OFFSET (memory_start >> PAGE_SHIFT)
# endif /* __ASSEMBLER__ */
/* Convert between virtual and physical address for MMU. */
/* Handle MicroBlaze processor with virtual memory. */
#define __virt_to_phys(addr) \
((addr) + CONFIG_KERNEL_BASE_ADDR - CONFIG_KERNEL_START)
#define __phys_to_virt(addr) \
((addr) + CONFIG_KERNEL_START - CONFIG_KERNEL_BASE_ADDR)
#define tophys(rd, rs) \
addik rd, rs, (CONFIG_KERNEL_BASE_ADDR - CONFIG_KERNEL_START)
#define tovirt(rd, rs) \
addik rd, rs, (CONFIG_KERNEL_START - CONFIG_KERNEL_BASE_ADDR)
#ifndef __ASSEMBLER__
# define __pa(x) __virt_to_phys((unsigned long)(x))
# define __va(x) ((void *)__phys_to_virt((unsigned long)(x)))
static inline unsigned long virt_to_pfn(const void *vaddr)
{
return phys_to_pfn(__pa(vaddr));
}
static inline const void *pfn_to_virt(unsigned long pfn)
{
return __va(pfn_to_phys((pfn)));
}
#define virt_addr_valid(vaddr) (pfn_valid(virt_to_pfn(vaddr)))
#endif /* __ASSEMBLER__ */
#define TOPHYS(addr) __virt_to_phys(addr)
#endif /* __KERNEL__ */
#include <asm-generic/memory_model.h>
#include <asm-generic/getorder.h>
#endif /* _ASM_MICROBLAZE_PAGE_H */