Release 4.7 mm/swap_state.c

/*
 *  linux/mm/swap_state.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 *
 *  Rewritten to use page cache, (C) 1998 Stephen Tweedie
 */
#include <linux/mm.h>
#include <linux/gfp.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/init.h>
#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/blkdev.h>
#include <linux/pagevec.h>
#include <linux/migrate.h>

#include <asm/pgtable.h>

/*
 * swapper_space is a fiction, retained to simplify the path through
 * vmscan's shrink_page_list.
 */

static const struct address_space_operations swap_aops = {
	.writepage	= swap_writepage,
	.set_page_dirty	= swap_set_page_dirty,
#ifdef CONFIG_MIGRATION
	.migratepage	= migrate_page,
#endif
};


struct address_space swapper_spaces[MAX_SWAPFILES] = {
	[0 ... MAX_SWAPFILES - 1] = {
		.page_tree	= RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
		.i_mmap_writable = ATOMIC_INIT(0),
		.a_ops		= &swap_aops,
        }
};


#define INC_CACHE_INFO(x)	do { swap_cache_info.x++; } while (0)

static struct {
	
unsigned long add_total;
	
unsigned long del_total;
	
unsigned long find_success;
	
unsigned long find_total;
} 
swap_cache_info;



unsigned long total_swapcache_pages(void)
{
	int i;
	unsigned long ret = 0;

	for (i = 0; i < MAX_SWAPFILES; i++)
		ret += swapper_spaces[i].nrpages;
	return ret;
}

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static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);



void show_swap_cache_info(void)
{
	printk("%lu pages in swap cache\n", total_swapcache_pages());
	printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
		swap_cache_info.add_total, swap_cache_info.del_total,
		swap_cache_info.find_success, swap_cache_info.find_total);
	printk("Free swap  = %ldkB\n",
		get_nr_swap_pages() << (PAGE_SHIFT - 10));
	printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
}

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linus torvalds
13
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johannes weiner
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1
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shaohua li
3
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hugh dickins
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/*
 * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
 * but sets SwapCache flag and private instead of mapping and index.
 */


int __add_to_swap_cache(struct page *page, swp_entry_t entry)
{
	int error;
	struct address_space *address_space;

	VM_BUG_ON_PAGE(!PageLocked(page), page);
	VM_BUG_ON_PAGE(PageSwapCache(page), page);
	VM_BUG_ON_PAGE(!PageSwapBacked(page), page);

	get_page(page);
	SetPageSwapCache(page);
	set_page_private(page, entry.val);

	address_space = swap_address_space(entry);
	spin_lock_irq(&address_space->tree_lock);
	error = radix_tree_insert(&address_space->page_tree,
					entry.val, page);
	if (likely(!error)) {
		address_space->nrpages++;
		__inc_zone_page_state(page, NR_FILE_PAGES);
		INC_CACHE_INFO(add_total);
	}
	spin_unlock_irq(&address_space->tree_lock);

	if (unlikely(error)) {
		/*
                 * Only the context which have set SWAP_HAS_CACHE flag
                 * would call add_to_swap_cache().
                 * So add_to_swap_cache() doesn't returns -EEXIST.
                 */
		VM_BUG_ON(error == -EEXIST);
		set_page_private(page, 0UL);
		ClearPageSwapCache(page);
		put_page(page);
	}

	return error;
}


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21
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daisuke nishimura
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7.95%
2
11.11%
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pre-git
11
6.25%
4
22.22%
sasha levin
sasha levin
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5.11%
1
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rik van riel
8
4.55%
1
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hugh dickins
5
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christoph lameter
4
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kirill a. shutemov
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linus torvalds
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int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
{
	int error;

	error = radix_tree_maybe_preload(gfp_mask);
	if (!error) {
		error = __add_to_swap_cache(page, entry);
		radix_tree_preload_end();
	}
	return error;
}

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jan kara
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/*
 * This must be called only on pages that have
 * been verified to be in the swap cache.
 */


void __delete_from_swap_cache(struct page *page)
{
	swp_entry_t entry;
	struct address_space *address_space;

	VM_BUG_ON_PAGE(!PageLocked(page), page);
	VM_BUG_ON_PAGE(!PageSwapCache(page), page);
	VM_BUG_ON_PAGE(PageWriteback(page), page);

	entry.val = page_private(page);
	address_space = swap_address_space(entry);
	radix_tree_delete(&address_space->page_tree, page_private(page));
	set_page_private(page, 0);
	ClearPageSwapCache(page);
	address_space->nrpages--;
	__dec_zone_page_state(page, NR_FILE_PAGES);
	INC_CACHE_INFO(del_total);
}

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linus torvalds
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3
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sasha levin
sasha levin
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1
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hugh dickins
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christoph lameter
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/**
 * add_to_swap - allocate swap space for a page
 * @page: page we want to move to swap
 *
 * Allocate swap space for the page and add the page to the
 * swap cache.  Caller needs to hold the page lock. 
 */


int add_to_swap(struct page *page, struct list_head *list)
{
	swp_entry_t entry;
	int err;

	VM_BUG_ON_PAGE(!PageLocked(page), page);
	VM_BUG_ON_PAGE(!PageUptodate(page), page);

	entry = get_swap_page();
	if (!entry.val)
		return 0;

	if (mem_cgroup_try_charge_swap(page, entry)) {
		swapcache_free(entry);
		return 0;
	}

	if (unlikely(PageTransHuge(page)))
		if (unlikely(split_huge_page_to_list(page, list))) {
			swapcache_free(entry);
			return 0;
		}

	/*
         * Radix-tree node allocations from PF_MEMALLOC contexts could
         * completely exhaust the page allocator. __GFP_NOMEMALLOC
         * stops emergency reserves from being allocated.
         *
         * TODO: this could cause a theoretical memory reclaim
         * deadlock in the swap out path.
         */
	/*
         * Add it to the swap cache.
         */
	err = add_to_swap_cache(page, entry,
			__GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);

	if (!err) {
		return 1;
	} else {	/* -ENOMEM radix-tree allocation failure */
		/*
                 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
                 * clear SWAP_HAS_CACHE flag.
                 */
		swapcache_free(entry);
		return 0;
	}
}

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shaohua li
8
5.37%
1
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hugh dickins
7
4.70%
3
17.65%
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daisuke nishimura
7
4.70%
1
5.88%
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sasha levin
6
4.03%
1
5.88%
eric sesterhenn
eric sesterhenn
2
1.34%
1
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kamezawa hiroyuki
1
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1
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minchan kim
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/*
 * This must be called only on pages that have
 * been verified to be in the swap cache and locked.
 * It will never put the page into the free list,
 * the caller has a reference on the page.
 */


void delete_from_swap_cache(struct page *page)
{
	swp_entry_t entry;
	struct address_space *address_space;

	entry.val = page_private(page);

	address_space = swap_address_space(entry);
	spin_lock_irq(&address_space->tree_lock);
	__delete_from_swap_cache(page);
	spin_unlock_irq(&address_space->tree_lock);

	swapcache_free(entry);
	put_page(page);
}

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linus torvalds
11
16.92%
1
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hugh dickins
3
4.62%
1
7.69%
nick piggin
nick piggin
2
3.08%
1
7.69%
andrew morton
andrew morton
2
3.08%
1
7.69%
kirill a. shutemov
kirill a. shutemov
1
1.54%
1
7.69%
kamezawa hiroyuki
kamezawa hiroyuki
1
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1
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/* 
 * If we are the only user, then try to free up the swap cache. 
 * 
 * Its ok to check for PageSwapCache without the page lock
 * here because we are going to recheck again inside
 * try_to_free_swap() _with_ the lock.
 *                                      - Marcelo
 */


static inline void free_swap_cache(struct page *page)
{
	if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
		try_to_free_swap(page);
		unlock_page(page);
	}
}

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andrew morton
5
11.90%
2
40.00%
nick piggin
nick piggin
1
2.38%
1
20.00%
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42
100.00%
5
100.00%

/* 
 * Perform a free_page(), also freeing any swap cache associated with
 * this page if it is the last user of the page.
 */


void free_page_and_swap_cache(struct page *page)
{
	free_swap_cache(page);
	if (is_huge_zero_page(page))
		put_huge_zero_page();
	else
		put_page(page);
}

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1
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linus torvalds
linus torvalds
5
16.13%
1
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kirill a. shutemov
kirill a. shutemov
1
3.23%
1
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31
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4
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/*
 * Passed an array of pages, drop them all from swapcache and then release
 * them.  They are removed from the LRU and freed if this is their last use.
 */


void free_pages_and_swap_cache(struct page **pages, int nr)
{
	struct page **pagep = pages;
	int i;

	lru_add_drain();
	for (i = 0; i < nr; i++)
		free_swap_cache(pagep[i]);
	release_pages(pagep, nr, false);
}

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1
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mel gorman
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1
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/*
 * Lookup a swap entry in the swap cache. A found page will be returned
 * unlocked and with its refcount incremented - we rely on the kernel
 * lock getting page table operations atomic even if we drop the page
 * lock before returning.
 */


struct page * lookup_swap_cache(swp_entry_t entry)
{
	struct page *page;

	page = find_get_page(swap_address_space(entry), entry.val);

	if (page) {
		INC_CACHE_INFO(find_success);
		if (TestClearPageReadahead(page))
			atomic_inc(&swapin_readahead_hits);
	}

	INC_CACHE_INFO(find_total);
	return page;
}

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20.00%
andrew morton
andrew morton
9
14.75%
1
10.00%
linus torvalds
linus torvalds
4
6.56%
1
10.00%
marcelo tosatti
marcelo tosatti
1
1.64%
1
10.00%
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61
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10
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struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
			struct vm_area_struct *vma, unsigned long addr,
			bool *new_page_allocated)
{
	struct page *found_page, *new_page = NULL;
	struct address_space *swapper_space = swap_address_space(entry);
	int err;
	*new_page_allocated = false;

	do {
		/*
                 * First check the swap cache.  Since this is normally
                 * called after lookup_swap_cache() failed, re-calling
                 * that would confuse statistics.
                 */
		found_page = find_get_page(swapper_space, entry.val);
		if (found_page)
			break;

		/*
                 * Get a new page to read into from swap.
                 */
		if (!new_page) {
			new_page = alloc_page_vma(gfp_mask, vma, addr);
			if (!new_page)
				break;		/* Out of memory */
		}

		/*
                 * call radix_tree_preload() while we can wait.
                 */
		err = radix_tree_maybe_preload(gfp_mask & GFP_KERNEL);
		if (err)
			break;

		/*
                 * Swap entry may have been freed since our caller observed it.
                 */
		err = swapcache_prepare(entry);
		if (err == -EEXIST) {
			radix_tree_preload_end();
			/*
                         * We might race against get_swap_page() and stumble
                         * across a SWAP_HAS_CACHE swap_map entry whose page
                         * has not been brought into the swapcache yet, while
                         * the other end is scheduled away waiting on discard
                         * I/O completion at scan_swap_map().
                         *
                         * In order to avoid turning this transitory state
                         * into a permanent loop around this -EEXIST case
                         * if !CONFIG_PREEMPT and the I/O completion happens
                         * to be waiting on the CPU waitqueue where we are now
                         * busy looping, we just conditionally invoke the
                         * scheduler here, if there are some more important
                         * tasks to run.
                         */
			cond_resched();
			continue;
		}
		if (err) {		/* swp entry is obsolete ? */
			radix_tree_preload_end();
			break;
		}

		/* May fail (-ENOMEM) if radix-tree node allocation failed. */
		__SetPageLocked(new_page);
		__SetPageSwapBacked(new_page);
		err = __add_to_swap_cache(new_page, entry);
		if (likely(!err)) {
			radix_tree_preload_end();
			/*
                         * Initiate read into locked page and return.
                         */
			lru_cache_add_anon(new_page);
			*new_page_allocated = true;
			return new_page;
		}
		radix_tree_preload_end();
		__ClearPageLocked(new_page);
		/*
                 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
                 * clear SWAP_HAS_CACHE flag.
                 */
		swapcache_free(entry);
	} while (err != -ENOMEM);

	if (new_page)
		put_page(new_page);
	return found_page;
}

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linus torvalds
43
18.53%
4
14.81%
daisuke nishimura
daisuke nishimura
33
14.22%
2
7.41%
dmitry safonov
dmitry safonov
25
10.78%
1
3.70%
hugh dickins
hugh dickins
23
9.91%
3
11.11%
andrew morton
andrew morton
20
8.62%
4
14.81%
kamezawa hiroyuki
kamezawa hiroyuki
17
7.33%
2
7.41%
rik van riel
rik van riel
5
2.16%
2
7.41%
rafael aquini
rafael aquini
4
1.72%
1
3.70%
kirill a. shutemov
kirill a. shutemov
3
1.29%
2
7.41%
nick piggin
nick piggin
3
1.29%
1
3.70%
marcelo tosatti
marcelo tosatti
1
0.43%
1
3.70%
jan kara
jan kara
1
0.43%
1
3.70%
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232
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27
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/*
 * Locate a page of swap in physical memory, reserving swap cache space
 * and reading the disk if it is not already cached.
 * A failure return means that either the page allocation failed or that
 * the swap entry is no longer in use.
 */


struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
			struct vm_area_struct *vma, unsigned long addr)
{
	bool page_was_allocated;
	struct page *retpage = __read_swap_cache_async(entry, gfp_mask,
			vma, addr, &page_was_allocated);

	if (page_was_allocated)
		swap_readpage(retpage);

	return retpage;
}

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static unsigned long swapin_nr_pages(unsigned long offset)
{
	static unsigned long prev_offset;
	unsigned int pages, max_pages, last_ra;
	static atomic_t last_readahead_pages;

	max_pages = 1 << READ_ONCE(page_cluster);
	if (max_pages <= 1)
		return 1;

	/*
         * This heuristic has been found to work well on both sequential and
         * random loads, swapping to hard disk or to SSD: please don't ask
         * what the "+ 2" means, it just happens to work well, that's all.
         */
	pages = atomic_xchg(&swapin_readahead_hits, 0) + 2;
	if (pages == 2) {
		/*
                 * We can have no readahead hits to judge by: but must not get
                 * stuck here forever, so check for an adjacent offset instead
                 * (and don't even bother to check whether swap type is same).
                 */
		if (offset != prev_offset + 1 && offset != prev_offset - 1)
			pages = 1;
		prev_offset = offset;
	} else {
		unsigned int roundup = 4;
		while (roundup < pages)
			roundup <<= 1;
		pages = roundup;
	}

	if (pages > max_pages)
		pages = max_pages;

	/* Don't shrink readahead too fast */
	last_ra = atomic_read(&last_readahead_pages) / 2;
	if (pages < last_ra)
		pages = last_ra;
	atomic_set(&last_readahead_pages, pages);

	return pages;
}

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2
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/**
 * swapin_readahead - swap in pages in hope we need them soon
 * @entry: swap entry of this memory
 * @gfp_mask: memory allocation flags
 * @vma: user vma this address belongs to
 * @addr: target address for mempolicy
 *
 * Returns the struct page for entry and addr, after queueing swapin.
 *
 * Primitive swap readahead code. We simply read an aligned block of
 * (1 << page_cluster) entries in the swap area. This method is chosen
 * because it doesn't cost us any seek time.  We also make sure to queue
 * the 'original' request together with the readahead ones...
 *
 * This has been extended to use the NUMA policies from the mm triggering
 * the readahead.
 *
 * Caller must hold down_read on the vma->vm_mm if vma is not NULL.
 */


struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
			struct vm_area_struct *vma, unsigned long addr)
{
	struct page *page;
	unsigned long entry_offset = swp_offset(entry);
	unsigned long offset = entry_offset;
	unsigned long start_offset, end_offset;
	unsigned long mask;
	struct blk_plug plug;

	mask = swapin_nr_pages(offset) - 1;
	if (!mask)
		goto skip;

	/* Read a page_cluster sized and aligned cluster around offset. */
	start_offset = offset & ~mask;
	end_offset = offset | mask;
	if (!start_offset)	/* First page is swap header. */
		start_offset++;

	blk_start_plug(&plug);
	for (offset = start_offset; offset <= end_offset ; offset++) {
		/* Ok, do the async read-ahead now */
		page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
						gfp_mask, vma, addr);
		if (!page)
			continue;
		if (offset != entry_offset)
			SetPageReadahead(page);
		put_page(page);
	}
	blk_finish_plug(&plug);

	lru_add_drain();	/* Push any new pages onto the LRU now */
skip:
	return read_swap_cache_async(entry, gfp_mask, vma, addr);
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
hugh dickins
hugh dickins
97
52.43%
2
33.33%
shaohua li
shaohua li
37
20.00%
1
16.67%
rik van riel
rik van riel
34
18.38%
1
16.67%
christian ehrhardt
christian ehrhardt
16
8.65%
1
16.67%
kirill a. shutemov
kirill a. shutemov
1
0.54%
1
16.67%
Total
185
100.00%
6
100.00%

Overall Contributors
Person
Tokens
Prop
Commits
CommitProp
shaohua li
shaohua li
353
21.67%
4
4.04%
andrew morton
andrew morton
275
16.88%
18
18.18%
pre-git
pre-git
194
11.91%
18
18.18%
hugh dickins
hugh dickins
162
9.94%
13
13.13%
linus torvalds
linus torvalds
136
8.35%
5
5.05%
daisuke nishimura
daisuke nishimura
97
5.95%
2
2.02%
dmitry safonov
dmitry safonov
82
5.03%
1
1.01%
nick piggin
nick piggin
72
4.42%
6
6.06%
andrea arcangeli
andrea arcangeli
53
3.25%
2
2.02%
rik van riel
rik van riel
47
2.89%
3
3.03%
sasha levin
sasha levin
24
1.47%
1
1.01%
christian ehrhardt
christian ehrhardt
19
1.17%
1
1.01%
kamezawa hiroyuki
kamezawa hiroyuki
19
1.17%
2
2.02%
vladimir davydov
vladimir davydov
19
1.17%
1
1.01%
christoph lameter
christoph lameter
16
0.98%
3
3.03%
gerald schaefer
gerald schaefer
11
0.68%
1
1.01%
kirill a. shutemov
kirill a. shutemov
8
0.49%
2
2.02%
johannes weiner
johannes weiner
8
0.49%
1
1.01%
david herrmann
david herrmann
8
0.49%
1
1.01%
michal hocko
michal hocko
5
0.31%
1
1.01%
rafael aquini
rafael aquini
4
0.25%
1
1.01%
tejun heo
tejun heo
3
0.18%
1
1.01%
mel gorman
mel gorman
2
0.12%
2
2.02%
minchan kim
minchan kim
2
0.12%
2
2.02%
marcelo tosatti
marcelo tosatti
2
0.12%
1
1.01%
eric sesterhenn
eric sesterhenn
2
0.12%
1
1.01%
jan kara
jan kara
2
0.12%
1
1.01%
christoph hellwig
christoph hellwig
1
0.06%
1
1.01%
randy dunlap
randy dunlap
1
0.06%
1
1.01%
jason low
jason low
1
0.06%
1
1.01%
jens axboe
jens axboe
1
0.06%
1
1.01%
Total
1629
100.00%
99
100.00%
  
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