The patch titled
Subject: mm/gup: add compound page list iterator
has been removed from the -mm tree. Its filename was
mm-gup-add-compound-page-list-iterator.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Joao Martins <joao.m.martins@xxxxxxxxxx>
Subject: mm/gup: add compound page list iterator
Patch series "mm/gup: page unpining improvements", v4.
This series improves page unpinning, with an eye on improving MR
deregistration for big swaths of memory (which is bound by the page
unpining), particularly:
1) Decrement the head page by @ntails and thus reducing a lot the
number of atomic operations per compound page. This is done by
comparing individual tail pages heads, and counting number of
consecutive tails on which they match heads and based on that update
head page refcount. Should have a visible improvement in all page
(un)pinners which use compound pages
2) Introducing a new API for unpinning page ranges (to avoid the trick
in the previous item and be based on math), and use that in RDMA
ib_mem_release (used for mr deregistration).
Performance improvements: unpin_user_pages() for hugetlbfs and THP
improves ~3x (through gup_test) and RDMA MR dereg improves ~4.5x with the
new API. See patches 2 and 4 for those.
This patch (of 4):
Add a helper that iterates over head pages in a list of pages. It
essentially counts the tails until the next page to process has a
different head that the current. This is going to be used by
unpin_user_pages() family of functions, to batch the head page refcount
updates once for all passed consecutive tail pages.
Link: https://lkml.kernel.org/r/20210212130843.13865-1-joao.m.martins@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20210212130843.13865-2-joao.m.martins@xxxxxxxxxx
Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Doug Ledford <dledford@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
--- a/mm/gup.c~mm-gup-add-compound-page-list-iterator
+++ a/mm/gup.c
@@ -213,6 +213,32 @@ void unpin_user_page(struct page *page)
}
EXPORT_SYMBOL(unpin_user_page);
+static inline void compound_next(unsigned long i, unsigned long npages,
+ struct page **list, struct page **head,
+ unsigned int *ntails)
+{
+ struct page *page;
+ unsigned int nr;
+
+ if (i >= npages)
+ return;
+
+ page = compound_head(list[i]);
+ for (nr = i + 1; nr < npages; nr++) {
+ if (compound_head(list[nr]) != page)
+ break;
+ }
+
+ *head = page;
+ *ntails = nr - i;
+}
+
+#define for_each_compound_head(__i, __list, __npages, __head, __ntails) \
+ for (__i = 0, \
+ compound_next(__i, __npages, __list, &(__head), &(__ntails)); \
+ __i < __npages; __i += __ntails, \
+ compound_next(__i, __npages, __list, &(__head), &(__ntails)))
+
/**
* unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
* @pages: array of pages to be maybe marked dirty, and definitely released.
_
Patches currently in -mm which might be from joao.m.martins@xxxxxxxxxx are
