From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Dave Hansen <dave.hansen@intel.com>,
Hugh Dickins <hughd@google.com>, Mel Gorman <mgorman@suse.de>,
Rik van Riel <riel@redhat.com>, Vlastimil Babka <vbabka@suse.cz>,
Christoph Lameter <cl@gentwo.org>,
Steve Capper <steve.capper@linaro.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.cz>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH 06/19] mm: store mapcount for compound page separate
Date: Tue, 18 Nov 2014 08:43:00 +0000 [thread overview]
Message-ID: <20141118084337.GA16714@hori1.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <1415198994-15252-7-git-send-email-kirill.shutemov@linux.intel.com>
On Wed, Nov 05, 2014 at 04:49:41PM +0200, Kirill A. Shutemov wrote:
> We're going to allow mapping of individual 4k pages of THP compound and
> we need a cheap way to find out how many time the compound page is
> mapped with PMD -- compound_mapcount() does this.
>
> page_mapcount() counts both: PTE and PMD mappings of the page.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
...
> @@ -1837,6 +1839,9 @@ static void __split_huge_page_refcount(struct page *page,
> atomic_sub(tail_count, &page->_count);
> BUG_ON(atomic_read(&page->_count) <= 0);
>
> + page->_mapcount = *compound_mapcount_ptr(page);
Is atomic_set() necessary?
> + page[1].mapping = page->mapping;
> +
> __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
>
> ClearPageCompound(page);
...
> @@ -760,6 +763,8 @@ static bool free_pages_prepare(struct page *page, unsigned int order)
> bad += free_pages_check(page + i);
> if (bad)
> return false;
> + if (order)
> + page[1].mapping = NULL;
>
> if (!PageHighMem(page)) {
> debug_check_no_locks_freed(page_address(page),
> @@ -6632,10 +6637,12 @@ static void dump_page_flags(unsigned long flags)
> void dump_page_badflags(struct page *page, const char *reason,
> unsigned long badflags)
> {
> - printk(KERN_ALERT
> - "page:%p count:%d mapcount:%d mapping:%p index:%#lx\n",
> + pr_alert("page:%p count:%d mapcount:%d mapping:%p index:%#lx",
> page, atomic_read(&page->_count), page_mapcount(page),
> page->mapping, page->index);
> + if (PageCompound(page))
> + printk(" compound_mapcount: %d", compound_mapcount(page));
> + printk("\n");
These two printk() should be pr_alert(), too?
> dump_page_flags(page->flags);
> if (reason)
> pr_alert("page dumped because: %s\n", reason);
> diff --git a/mm/rmap.c b/mm/rmap.c
> index f706a6af1801..eecc9301847d 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -986,9 +986,30 @@ void page_add_anon_rmap(struct page *page,
> void do_page_add_anon_rmap(struct page *page,
> struct vm_area_struct *vma, unsigned long address, int flags)
> {
> - int first = atomic_inc_and_test(&page->_mapcount);
> + bool compound = flags & RMAP_COMPOUND;
> + bool first;
> +
> + VM_BUG_ON_PAGE(!PageLocked(compound_head(page)), page);
> +
> + if (PageTransCompound(page)) {
> + struct page *head_page = compound_head(page);
> +
> + if (compound) {
> + VM_BUG_ON_PAGE(!PageTransHuge(page), page);
> + first = atomic_inc_and_test(compound_mapcount_ptr(page));
Is compound_mapcount_ptr() well-defined for tail pages?
This function seems to access struct page of the page next to a given page,
so if the given page is the last tail page of a thp, page outside the thp
will be accessed. Do you have a prevention from this?
atomic_inc_and_test(compound_mapcount_ptr(head_page)) is what you intended?
> + } else {
> + /* Anon THP always mapped first with PMD */
> + first = 0;
> + VM_BUG_ON_PAGE(!compound_mapcount(head_page),
> + head_page);
> + atomic_inc(&page->_mapcount);
> + }
> + } else {
> + VM_BUG_ON_PAGE(compound, page);
> + first = atomic_inc_and_test(&page->_mapcount);
> + }
> +
> if (first) {
> - bool compound = flags & RMAP_COMPOUND;
> int nr = compound ? hpage_nr_pages(page) : 1;
> /*
> * We use the irq-unsafe __{inc|mod}_zone_page_stat because
...
> @@ -1032,10 +1052,19 @@ void page_add_new_anon_rmap(struct page *page,
>
> VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
> SetPageSwapBacked(page);
> - atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
> if (compound) {
> + atomic_t *compound_mapcount;
> +
> VM_BUG_ON_PAGE(!PageTransHuge(page), page);
> + compound_mapcount = (atomic_t *)&page[1].mapping;
You can use compound_mapcount_ptr() here.
Thanks,
Naoya Horiguchi
> + /* increment count (starts at -1) */
> + atomic_set(compound_mapcount, 0);
> __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
> + } else {
> + /* Anon THP always mapped first with PMD */
> + VM_BUG_ON_PAGE(PageTransCompound(page), page);
> + /* increment count (starts at -1) */
> + atomic_set(&page->_mapcount, 0);
> }
> __mod_zone_page_state(page_zone(page), NR_ANON_PAGES, nr);
> __page_set_anon_rmap(page, vma, address, 1);
next prev parent reply other threads:[~2014-11-18 8:47 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-05 14:49 [PATCHv2 RFC 00/19] THP refcounting redesign Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 01/19] mm, thp: drop FOLL_SPLIT Kirill A. Shutemov
2014-11-25 3:01 ` Naoya Horiguchi
2014-11-25 14:04 ` Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 02/19] thp: cluster split_huge_page* code together Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 03/19] mm: change PageAnon() to work on tail pages Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 04/19] mm: avoid PG_locked " Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 05/19] rmap: add argument to charge compound page Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 06/19] mm: store mapcount for compound page separate Kirill A. Shutemov
2014-11-18 8:43 ` Naoya Horiguchi [this message]
2014-11-18 9:58 ` Kirill A. Shutemov
2014-11-18 23:41 ` Naoya Horiguchi
2014-11-19 0:54 ` Kirill A. Shutemov
2014-11-21 6:41 ` Aneesh Kumar K.V
2014-11-21 11:47 ` Kirill A. Shutemov
2014-11-19 10:51 ` Jerome Marchand
2014-11-19 13:00 ` Kirill A. Shutemov
2014-11-19 13:15 ` Jerome Marchand
2014-11-20 20:06 ` Christoph Lameter
2014-11-21 12:01 ` Kirill A. Shutemov
2014-11-21 6:12 ` Aneesh Kumar K.V
2014-11-21 12:02 ` Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 07/19] mm, thp: adjust conditions when we can reuse the page on WP fault Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 08/19] mm: prepare migration code for new THP refcounting Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 09/19] thp: rename split_huge_page_pmd() to split_huge_pmd() Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 10/19] thp: PMD splitting without splitting compound page Kirill A. Shutemov
2014-11-19 6:57 ` Naoya Horiguchi
2014-11-19 13:02 ` Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 11/19] mm, vmstats: new THP splitting event Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 12/19] thp: implement new split_huge_page() Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 13/19] mm, thp: remove infrastructure for handling splitting PMDs Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 14/19] x86, thp: remove " Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 15/19] futex, thp: remove special case for THP in get_futex_key Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 16/19] thp: update documentation Kirill A. Shutemov
2014-11-19 8:07 ` Naoya Horiguchi
2014-11-19 13:11 ` Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 17/19] mlock, thp: HACK: split all pages in VM_LOCKED vma Kirill A. Shutemov
2014-11-19 9:02 ` Naoya Horiguchi
2014-11-19 13:08 ` Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 18/19] tho, mm: use migration entries to freeze page counts on split Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 19/19] mm, thp: remove compound_lock Kirill A. Shutemov
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