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>
#define STRICT_MM_TYPECHECKS
extern void clear_page(void *page);
-#define clear_user_page(page, vaddr, pg) clear_page(page)
#define vma_alloc_zeroed_movable_folio(vma, vaddr) \
vma_alloc_folio(GFP_HIGHUSER_MOVABLE | __GFP_ZERO, 0, vma, vaddr)
void copy_user_highpage(struct page *to, struct page *from,
unsigned long u_vaddr, struct vm_area_struct *vma);
+
+#define clear_user_page clear_user_page
void clear_user_page(void *to, unsigned long u_vaddr, struct page *page);
typedef struct {
#define clear_page(page) memset((page), 0, PAGE_SIZE)
#define copy_page(to,from) memcpy((to), (from), PAGE_SIZE)
-#define clear_user_page(page, vaddr, pg) clear_page(page)
#define copy_user_page(to, from, vaddr, pg) copy_page(to, from)
/*
bool tag_clear_highpages(struct page *to, int numpages);
#define __HAVE_ARCH_TAG_CLEAR_HIGHPAGES
-#define clear_user_page(page, vaddr, pg) clear_page(page)
#define copy_user_page(to, from, vaddr, pg) copy_page(to, from)
typedef struct page *pgtable_t;
return (addr1 ^ addr2) & (SHMLBA-1);
}
+#define clear_user_page clear_user_page
static inline void clear_user_page(void *addr, unsigned long vaddr,
struct page *page)
{
/* SPDX-License-Identifier: GPL-2.0 */
-
-static inline void clear_user_page(void *addr, unsigned long vaddr,
- struct page *page)
-{
- clear_page(addr);
-}
-
static inline void copy_user_page(void *to, void *from, unsigned long vaddr,
struct page *page)
{
/*
* Under assumption that kernel always "sees" user map...
*/
-#define clear_user_page(page, vaddr, pg) clear_page(page)
#define copy_user_page(to, from, vaddr, pg) copy_page(to, from)
static inline unsigned long virt_to_pfn(const void *kaddr)
extern void clear_page(void *page);
extern void copy_page(void *to, void *from);
-#define clear_user_page(page, vaddr, pg) clear_page(page)
#define copy_user_page(to, from, vaddr, pg) copy_page(to, from)
extern unsigned long shm_align_mask;
#define clear_page(page) memset((page), 0, PAGE_SIZE)
#define copy_page(to,from) memcpy((to), (from), PAGE_SIZE)
-#define clear_user_page(page, vaddr, pg) clear_page(page)
#define copy_user_page(to, from, vaddr, pg) copy_page(to, from)
#define vma_alloc_zeroed_movable_folio(vma, vaddr) \
# define copy_page(to, from) memcpy((to), (from), PAGE_SIZE)
# define clear_page(pgaddr) memset((pgaddr), 0, PAGE_SIZE)
-# define clear_user_page(pgaddr, vaddr, page) memset((pgaddr), 0, PAGE_SIZE)
# define copy_user_page(vto, vfrom, vaddr, topg) \
memcpy((vto), (vfrom), PAGE_SIZE)
if (pages_do_alias((unsigned long) addr, vaddr & PAGE_MASK))
flush_data_cache_page((unsigned long)addr);
}
+#define clear_user_page clear_user_page
struct vm_area_struct;
extern void copy_user_highpage(struct page *to, struct page *from,
struct page;
+#define clear_user_page clear_user_page
extern void clear_user_page(void *addr, unsigned long vaddr, struct page *page);
extern void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,
struct page *to);
#define clear_page(page) memset((page), 0, PAGE_SIZE)
#define copy_page(to, from) memcpy((to), (from), PAGE_SIZE)
-#define clear_user_page(page, vaddr, pg) clear_page(page)
#define copy_user_page(to, from, vaddr, pg) copy_page(to, from)
/*
void clear_page_asm(void *page);
void copy_page_asm(void *to, void *from);
-#define clear_user_page(vto, vaddr, page) clear_page_asm(vto)
void copy_user_highpage(struct page *to, struct page *from, unsigned long vaddr,
struct vm_area_struct *vma);
#define __HAVE_ARCH_COPY_USER_HIGHPAGE
struct page;
extern void clear_user_page(void *page, unsigned long vaddr, struct page *pg);
+#define clear_user_page clear_user_page
extern void copy_user_page(void *to, void *from, unsigned long vaddr,
struct page *p);
extern int devmem_is_allowed(unsigned long pfn);
#endif
#define copy_page(to, from) memcpy((to), (from), PAGE_SIZE)
-#define clear_user_page(pgaddr, vaddr, page) clear_page(pgaddr)
#define copy_user_page(vto, vfrom, vaddr, topg) \
memcpy((vto), (vfrom), PAGE_SIZE)
: : "memory", "cc");
}
-#define clear_user_page(page, vaddr, pg) clear_page(page)
#define copy_user_page(to, from, vaddr, pg) copy_page(to, from)
#define vma_alloc_zeroed_movable_folio(vma, vaddr) \
#define clear_page(X) _clear_page((void *)(X))
struct page;
void clear_user_page(void *addr, unsigned long vaddr, struct page *page);
+#define clear_user_page clear_user_page
#define copy_page(X,Y) memcpy((void *)(X), (void *)(Y), PAGE_SIZE)
void copy_user_page(void *to, void *from, unsigned long vaddr, struct page *topage);
#define __HAVE_ARCH_COPY_USER_HIGHPAGE
#define clear_page(page) memset((void *)(page), 0, PAGE_SIZE)
#define copy_page(to,from) memcpy((void *)(to), (void *)(from), PAGE_SIZE)
-#define clear_user_page(page, vaddr, pg) clear_page(page)
#define copy_user_page(to, from, vaddr, pg) copy_page(to, from)
typedef struct { unsigned long pte; } pte_t;
extern struct range pfn_mapped[];
extern int nr_pfn_mapped;
-static inline void clear_user_page(void *page, unsigned long vaddr,
- struct page *pg)
-{
- clear_page(page);
-}
-
static inline void copy_user_page(void *to, void *from, unsigned long vaddr,
struct page *topage)
{
void copy_user_highpage(struct page *to, struct page *from,
unsigned long vaddr, struct vm_area_struct *vma);
#else
-# define clear_user_page(page, vaddr, pg) clear_page(page)
# define copy_user_page(to, from, vaddr, pg) copy_page(to, from)
#endif
}
#endif
-/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
#ifndef clear_user_highpage
+#ifndef clear_user_page
+/**
+ * clear_user_page() - clear a page to be mapped to user space
+ * @addr: the address of the page
+ * @vaddr: the address of the user mapping
+ * @page: the page
+ *
+ * We condition the definition of clear_user_page() on the architecture
+ * not having a custom clear_user_highpage(). That's because if there
+ * is some special flushing needed for clear_user_highpage() then it
+ * is likely that clear_user_page() also needs some magic. And, since
+ * our only caller is the generic clear_user_highpage(), not defining
+ * is not much of a loss.
+ */
+static inline void clear_user_page(void *addr, unsigned long vaddr, struct page *page)
+{
+ clear_page(addr);
+}
+#endif
+
+/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
{
void *addr = kmap_local_page(page);
clear_user_page(addr, vaddr, page);
kunmap_local(addr);
}
-#endif
+#endif /* clear_user_highpage */
#ifndef vma_alloc_zeroed_movable_folio
/**
projects / thirdparty / kernel / stable.git / commitdiff
