Commit 8efd6f5b authored by Arjun Roy's avatar Arjun Roy Committed by Linus Torvalds
Browse files

mm/memory.c: refactor insert_page to prepare for batched-lock insert 



Add helper methods for vm_insert_page()/insert_page() to prepare for
vm_insert_pages(), which batch-inserts pages to reduce spinlock
operations when inserting multiple consecutive pages into the user page
table.

The intention of this patch-set is to reduce atomic ops for tcp zerocopy
receives, which normally hits the same spinlock multiple times
consecutively.

Signed-off-by: default avatarArjun Roy <arjunroy@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: David Miller <davem@davemloft.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Link: http://lkml.kernel.org/r/20200128025958.43490-1-arjunroy.kdev@gmail.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 09ef5283

mm/memory.c

+24 −15
Original line number Diff line number Diff line
@@ -1442,6 +1442,27 @@ pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr, 
	return pte_alloc_map_lock(mm, pmd, addr, ptl);

}



static int validate_page_before_insert(struct page *page)

{

	if (PageAnon(page) || PageSlab(page) || page_has_type(page))

		return -EINVAL;

	flush_dcache_page(page);

	return 0;

}



static int insert_page_into_pte_locked(struct mm_struct *mm, pte_t *pte,

			unsigned long addr, struct page *page, pgprot_t prot)

{

	if (!pte_none(*pte))

		return -EBUSY;

	/* Ok, finally just insert the thing.. */

	get_page(page);

	inc_mm_counter_fast(mm, mm_counter_file(page));

	page_add_file_rmap(page, false);

	set_pte_at(mm, addr, pte, mk_pte(page, prot));

	return 0;

}



/*

 * This is the old fallback for page remapping.

 *
@@ -1457,26 +1478,14 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr, 
	pte_t *pte;

	spinlock_t *ptl;



	retval = -EINVAL;

	if (PageAnon(page) || PageSlab(page) || page_has_type(page))

	retval = validate_page_before_insert(page);

	if (retval)

		goto out;

	retval = -ENOMEM;

	flush_dcache_page(page);

	pte = get_locked_pte(mm, addr, &ptl);

	if (!pte)

		goto out;

	retval = -EBUSY;

	if (!pte_none(*pte))

		goto out_unlock;



	/* Ok, finally just insert the thing.. */

	get_page(page);

	inc_mm_counter_fast(mm, mm_counter_file(page));

	page_add_file_rmap(page, false);

	set_pte_at(mm, addr, pte, mk_pte(page, prot));



	retval = 0;

out_unlock:

	retval = insert_page_into_pte_locked(mm, pte, addr, page, prot);

	pte_unmap_unlock(pte, ptl);

out:

	return retval;

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