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Date: Tue, 04 Sep 2012 08:21:17 -0700
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: Matthew Wilcox <willy@...ux.intel.com>
Cc: Mel Gorman <mel@....ul.ie>,
Andrew Morton <akpm@...ux-foundation.org>,
Minchan Kim <minchan@...nel.org>,
Johannes Weiner <hannes@...xchg.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Andi Kleen <ak@...ux.intel.com>, linux-mm@...ck.org,
linux-kernel <linux-kernel@...r.kernel.org>,
Alex Shi <alex.shi@...el.com>
Subject: Re: [RFC PATCH 2/2] mm: Batch page_check_references in
shrink_page_list sharing the same i_mmap_mutex
On Tue, 2012-08-21 at 17:48 -0700, Tim Chen wrote:
>
> Thanks to Matthew's suggestions on improving the patch. Here's the
> updated version. It seems to be sane when I booted my machine up. I
> will put it through more testing when I get a chance.
>
> Tim
>
Matthew,
The new patch seems to be causing some of the workloads with mmaped file
read to seg fault. Will need to dig further to find out why.
Tim
> ---
> Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
> ---
> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
> index fd07c45..f1320b1 100644
> --- a/include/linux/rmap.h
> +++ b/include/linux/rmap.h
> @@ -156,8 +156,11 @@ static inline void page_dup_rmap(struct page *page)
> /*
> * Called from mm/vmscan.c to handle paging out
> */
> -int page_referenced(struct page *, int is_locked,
> - struct mem_cgroup *memcg, unsigned long *vm_flags);
> +int needs_page_mmap_mutex(struct page *page);
> +int page_referenced(struct page *, int is_locked, struct mem_cgroup *memcg,
> + unsigned long *vm_flags);
> +int __page_referenced(struct page *, int is_locked, struct mem_cgroup *memcg,
> + unsigned long *vm_flags);
> int page_referenced_one(struct page *, struct vm_area_struct *,
> unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
>
> @@ -176,6 +179,7 @@ enum ttu_flags {
> bool is_vma_temporary_stack(struct vm_area_struct *vma);
>
> int try_to_unmap(struct page *, enum ttu_flags flags);
> +int __try_to_unmap(struct page *, enum ttu_flags flags);
> int try_to_unmap_one(struct page *, struct vm_area_struct *,
> unsigned long address, enum ttu_flags flags);
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 5b5ad58..ca8cd21 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -843,8 +843,7 @@ static int page_referenced_file(struct page *page,
> * so we can safely take mapping->i_mmap_mutex.
> */
> BUG_ON(!PageLocked(page));
> -
> - mutex_lock(&mapping->i_mmap_mutex);
> + BUG_ON(!mutex_is_locked(&mapping->i_mmap_mutex));
>
> /*
> * i_mmap_mutex does not stabilize mapcount at all, but mapcount
> @@ -869,21 +868,16 @@ static int page_referenced_file(struct page *page,
> break;
> }
>
> - mutex_unlock(&mapping->i_mmap_mutex);
> return referenced;
> }
>
> -/**
> - * page_referenced - test if the page was referenced
> - * @page: the page to test
> - * @is_locked: caller holds lock on the page
> - * @memcg: target memory cgroup
> - * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
> - *
> - * Quick test_and_clear_referenced for all mappings to a page,
> - * returns the number of ptes which referenced the page.
> - */
> -int page_referenced(struct page *page,
> +int needs_page_mmap_mutex(struct page *page)
> +{
> + return page->mapping && page_mapped(page) && page_rmapping(page) &&
> + !PageKsm(page) && !PageAnon(page);
> +}
> +
> +int __page_referenced(struct page *page,
> int is_locked,
> struct mem_cgroup *memcg,
> unsigned long *vm_flags)
> @@ -919,6 +913,32 @@ out:
> return referenced;
> }
>
> +/**
> + * page_referenced - test if the page was referenced
> + * @page: the page to test
> + * @is_locked: caller holds lock on the page
> + * @memcg: target memory cgroup
> + * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
> + *
> + * Quick test_and_clear_referenced for all mappings to a page,
> + * returns the number of ptes which referenced the page.
> + */
> +int page_referenced(struct page *page,
> + int is_locked,
> + struct mem_cgroup *memcg,
> + unsigned long *vm_flags)
> +{
> + int result, needs_lock;
> +
> + needs_lock = needs_page_mmap_mutex(page);
> + if (needs_lock)
> + mutex_lock(&page->mapping->i_mmap_mutex);
> + result = __page_referenced(page, is_locked, memcg, vm_flags);
> + if (needs_lock)
> + mutex_unlock(&page->mapping->i_mmap_mutex);
> + return result;
> +}
> +
> static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
> unsigned long address)
> {
> @@ -1560,7 +1580,7 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
> unsigned long max_nl_size = 0;
> unsigned int mapcount;
>
> - mutex_lock(&mapping->i_mmap_mutex);
> + BUG_ON(!mutex_is_locked(&mapping->i_mmap_mutex));
> vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
> unsigned long address = vma_address(page, vma);
> if (address == -EFAULT)
> @@ -1640,7 +1660,24 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
> list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
> vma->vm_private_data = NULL;
> out:
> - mutex_unlock(&mapping->i_mmap_mutex);
> + return ret;
> +}
> +
> +int __try_to_unmap(struct page *page, enum ttu_flags flags)
> +{
> + int ret;
> +
> + BUG_ON(!PageLocked(page));
> + VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
> +
> + if (unlikely(PageKsm(page)))
> + ret = try_to_unmap_ksm(page, flags);
> + else if (PageAnon(page))
> + ret = try_to_unmap_anon(page, flags);
> + else
> + ret = try_to_unmap_file(page, flags);
> + if (ret != SWAP_MLOCK && !page_mapped(page))
> + ret = SWAP_SUCCESS;
> return ret;
> }
>
> @@ -1660,20 +1697,27 @@ out:
> */
> int try_to_unmap(struct page *page, enum ttu_flags flags)
> {
> - int ret;
> + int result, needs_lock;
> +
> + needs_lock = needs_page_mmap_mutex(page);
> + if (needs_lock)
> + mutex_lock(&page->mapping->i_mmap_mutex);
> + result = __try_to_unmap(page, flags);
> + if (needs_lock)
> + mutex_unlock(&page->mapping->i_mmap_mutex);
> + return result;
> +}
>
> - BUG_ON(!PageLocked(page));
> - VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
> +int __try_to_munlock(struct page *page)
> +{
> + VM_BUG_ON(!PageLocked(page) || PageLRU(page));
>
> if (unlikely(PageKsm(page)))
> - ret = try_to_unmap_ksm(page, flags);
> + return try_to_unmap_ksm(page, TTU_MUNLOCK);
> else if (PageAnon(page))
> - ret = try_to_unmap_anon(page, flags);
> + return try_to_unmap_anon(page, TTU_MUNLOCK);
> else
> - ret = try_to_unmap_file(page, flags);
> - if (ret != SWAP_MLOCK && !page_mapped(page))
> - ret = SWAP_SUCCESS;
> - return ret;
> + return try_to_unmap_file(page, TTU_MUNLOCK);
> }
>
> /**
> @@ -1693,14 +1737,15 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
> */
> int try_to_munlock(struct page *page)
> {
> - VM_BUG_ON(!PageLocked(page) || PageLRU(page));
> -
> - if (unlikely(PageKsm(page)))
> - return try_to_unmap_ksm(page, TTU_MUNLOCK);
> - else if (PageAnon(page))
> - return try_to_unmap_anon(page, TTU_MUNLOCK);
> - else
> - return try_to_unmap_file(page, TTU_MUNLOCK);
> + int result, needs_lock;
> +
> + needs_lock = needs_page_mmap_mutex(page);
> + if (needs_lock)
> + mutex_lock(&page->mapping->i_mmap_mutex);
> + result = __try_to_munlock(page);
> + if (needs_lock)
> + mutex_unlock(&page->mapping->i_mmap_mutex);
> + return result;
> }
>
> void __put_anon_vma(struct anon_vma *anon_vma)
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index d4ab646..74a5fd0 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -27,6 +27,7 @@
> buffer_heads_over_limit */
> #include <linux/mm_inline.h>
> #include <linux/backing-dev.h>
> +#include <linux/ksm.h>
> #include <linux/rmap.h>
> #include <linux/topology.h>
> #include <linux/cpu.h>
> @@ -786,7 +787,7 @@ static enum page_references page_check_references(struct page *page,
> int referenced_ptes, referenced_page;
> unsigned long vm_flags;
>
> - referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags);
> + referenced_ptes = __page_referenced(page, 1, mz->mem_cgroup, &vm_flags);
> referenced_page = TestClearPageReferenced(page);
>
> /* Lumpy reclaim - ignore references */
> @@ -856,6 +857,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> unsigned long nr_congested = 0;
> unsigned long nr_reclaimed = 0;
> unsigned long nr_writeback = 0;
> + struct mutex *i_mmap_mutex = NULL;
>
> cond_resched();
>
> @@ -909,7 +911,15 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> }
> }
>
> + if (needs_page_mmap_mutex(page) &&
> + i_mmap_mutex != &page->mapping->i_mmap_mutex) {
> + if (i_mmap_mutex)
> + mutex_unlock(i_mmap_mutex);
> + i_mmap_mutex = &page->mapping->i_mmap_mutex;
> + mutex_lock(i_mmap_mutex);
> + }
> references = page_check_references(page, mz, sc);
> +
> switch (references) {
> case PAGEREF_ACTIVATE:
> goto activate_locked;
> @@ -939,7 +949,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> * processes. Try to unmap it here.
> */
> if (page_mapped(page) && mapping) {
> - switch (try_to_unmap(page, TTU_UNMAP)) {
> + switch (__try_to_unmap(page, TTU_UNMAP)) {
> case SWAP_FAIL:
> goto activate_locked;
> case SWAP_AGAIN:
> @@ -1090,6 +1100,8 @@ keep_lumpy:
> VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
> }
>
> + if (i_mmap_mutex)
> + mutex_unlock(i_mmap_mutex);
> nr_reclaimed += __remove_mapping_batch(&unmap_pages, &ret_pages,
> &free_pages);
>
>
>
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