The patch titled
mm: introduce get_user_pages_fast
has been removed from the -mm tree. Its filename was
mm-introduce-get_user_pages_fast.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: mm: introduce get_user_pages_fast
From: Nick Piggin <npiggin@xxxxxxx>
Introduce a new get_user_pages_fast mm API, which is basically a
get_user_pages with a less general API (but still tends to be suited to
the common case):
- task and mm are always current and current->mm
- force is always 0
- pages is always non-NULL
- don't pass back vmas
This restricted API can be implemented in a much more scalable way on many
architectures when the ptes are present, by walking the page tables
locklessly (no mmap_sem or page table locks). When the ptes are not
populated, get_user_pages_fast() could be slower.
This is implemented locklessly on x86, and used in some key direct IO call
sites, in later patches, which provides nearly 10% performance improvement
on a threaded database workload.
Lots of other code could use this too, depending on use cases (eg. grep
drivers/). And it might inspire some new and clever ways to use it.
[akpm@xxxxxxxxxxxxxxxxxxxx: build fix]
[akpm@xxxxxxxxxxxxxxxxxxxx: coding-style fixes]
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
Cc: Dave Kleikamp <shaggy@xxxxxxxxxxxxxx>
Cc: Andy Whitcroft <apw@xxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Dave Kleikamp <shaggy@xxxxxxxxxxxxxx>
Cc: Badari Pulavarty <pbadari@xxxxxxxxxx>
Cc: Zach Brown <zach.brown@xxxxxxxxxx>
Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
Reviewed-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff -puN include/linux/mm.h~mm-introduce-get_user_pages_fast include/linux/mm.h
--- a/include/linux/mm.h~mm-introduce-get_user_pages_fast
+++ a/include/linux/mm.h
@@ -833,6 +833,39 @@ extern int mprotect_fixup(struct vm_area
struct vm_area_struct **pprev, unsigned long start,
unsigned long end, unsigned long newflags);
+#ifdef CONFIG_HAVE_GET_USER_PAGES_FAST
+/*
+ * get_user_pages_fast provides equivalent functionality to get_user_pages,
+ * operating on current and current->mm (force=0 and doesn't return any vmas).
+ *
+ * get_user_pages_fast may take mmap_sem and page tables, so no assumptions
+ * can be made about locking. get_user_pages_fast is to be implemented in a
+ * way that is advantageous (vs get_user_pages()) when the user memory area is
+ * already faulted in and present in ptes. However if the pages have to be
+ * faulted in, it may turn out to be slightly slower).
+ */
+int get_user_pages_fast(unsigned long start, int nr_pages, int write,
+ struct page **pages);
+
+#else
+/*
+ * Should probably be moved to asm-generic, and architectures can include it if
+ * they don't implement their own get_user_pages_fast.
+ */
+#define get_user_pages_fast(start, nr_pages, write, pages) \
+({ \
+ struct mm_struct *mm = current->mm; \
+ int ret; \
+ \
+ down_read(&mm->mmap_sem); \
+ ret = get_user_pages(current, mm, start, nr_pages, \
+ write, 0, pages, NULL); \
+ up_read(&mm->mmap_sem); \
+ \
+ ret; \
+})
+#endif
+
/*
* A callback you can register to apply pressure to ageable caches.
*
_
Patches currently in -mm which might be from npiggin@xxxxxxx are
origin.patch
linux-next.patch
mmu-notifiers-add-list_del_init_rcu.patch
mmu-notifiers-add-mm_take_all_locks-operation.patch
mmu-notifier-core.patch
powerpc-implement-pte_special.patch
powerpc-implement-pte_special-update.patch
powerpc-lockless-get_user_pages.patch
vmscan-move-isolate_lru_page-to-vmscanc.patch
vmscan-move-isolate_lru_page-to-vmscanc-fix.patch
vmscan-split-lru-lists-into-anon-file-sets-splitlru-bdi_cap_swap_backed.patch
mlock-mlocked-pages-are-unevictable.patch
mlock-mlocked-pages-are-unevictable-fix.patch
mlock-mlocked-pages-are-unevictable-fix-fix.patch
mlock-mlocked-pages-are-unevictable-fix-3.patch
mlock-mlocked-pages-are-unevictable-fix-fix-munlock-page-table-walk-now-requires-mm.patch
mmap-handle-mlocked-pages-during-map-remap-unmap.patch
mmap-handle-mlocked-pages-during-map-remap-unmap-cleanup.patch
fix-double-unlock_page-in-2626-rc5-mm3-kernel-bug-at-mm-filemapc-575.patch
vmstat-mlocked-pages-statistics.patch
vmstat-mlocked-pages-statistics-fix-incorrect-mlocked-field-of-proc-meminfo.patch
reiser4.patch
likeliness-accounting-change-and-cleanup.patch
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