This looks good from our side - thanks! Reviewed-by: mwilliamson@xxxxxxxxxxxxxxxxx Tested-by: mwilliamson@xxxxxxxxxxxxxxxxx On Tue, Jun 9, 2015 at 9:00 PM, Konstantin Khlebnikov <koct9i@xxxxxxxxx> wrote: > From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> > > This patch sets bit 56 in pagemap if this page is mapped only once. > It allows to detect exclusively used pages without exposing PFN: > > present file exclusive state > 0 0 0 non-present > 1 1 0 file page mapped somewhere else > 1 1 1 file page mapped only here > 1 0 0 anon non-CoWed page (shared with parent/child) > 1 0 1 anon CoWed page (or never forked) > > CoWed pages in MAP_FILE|MAP_PRIVATE areas are anon in this context. > > Mmap-exclusive bit doesn't reflect potential page-sharing via swapcache: > page could be mapped once but has several swap-ptes which point to it. > Application could detect that by swap bit in pagemap entry and touch > that pte via /proc/pid/mem to get real information. > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> > Link: http://lkml.kernel.org/r/CAEVpBa+_RyACkhODZrRvQLs80iy0sqpdrd0AaP_-tgnX3Y9yNQ@xxxxxxxxxxxxxx > > --- > > v2: > * handle transparent huge pages > * invert bit and rename shared -> exclusive (less confusing name) > --- > Documentation/vm/pagemap.txt | 3 ++- > fs/proc/task_mmu.c | 10 ++++++++++ > tools/vm/page-types.c | 12 ++++++++++++ > 3 files changed, 24 insertions(+), 1 deletion(-) > > diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt > index 6bfbc17..3cfbbb3 100644 > --- a/Documentation/vm/pagemap.txt > +++ b/Documentation/vm/pagemap.txt > @@ -16,7 +16,8 @@ There are three components to pagemap: > * Bits 0-4 swap type if swapped > * Bits 5-54 swap offset if swapped > * Bit 55 pte is soft-dirty (see Documentation/vm/soft-dirty.txt) > - * Bits 56-60 zero > + * Bit 56 page exlusively mapped > + * Bits 57-60 zero > * Bit 61 page is file-page or shared-anon > * Bit 62 page swapped > * Bit 63 page present > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 21bc251..b02e38f 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -982,6 +982,7 @@ struct pagemapread { > #define PM_STATUS2(v2, x) (__PM_PSHIFT(v2 ? x : PAGE_SHIFT)) > > #define __PM_SOFT_DIRTY (1LL) > +#define __PM_MMAP_EXCLUSIVE (2LL) > #define PM_PRESENT PM_STATUS(4LL) > #define PM_SWAP PM_STATUS(2LL) > #define PM_FILE PM_STATUS(1LL) > @@ -1074,6 +1075,8 @@ static void pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm, > > if (page && !PageAnon(page)) > flags |= PM_FILE; > + if (page && page_mapcount(page) == 1) > + flags2 |= __PM_MMAP_EXCLUSIVE; > if ((vma->vm_flags & VM_SOFTDIRTY)) > flags2 |= __PM_SOFT_DIRTY; > > @@ -1119,6 +1122,13 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > else > pmd_flags2 = 0; > > + if (pmd_present(*pmd)) { > + struct page *page = pmd_page(*pmd); > + > + if (page_mapcount(page) == 1) > + pmd_flags2 |= __PM_MMAP_EXCLUSIVE; > + } > + > for (; addr != end; addr += PAGE_SIZE) { > unsigned long offset; > pagemap_entry_t pme; > diff --git a/tools/vm/page-types.c b/tools/vm/page-types.c > index 8bdf16b..3a9f193 100644 > --- a/tools/vm/page-types.c > +++ b/tools/vm/page-types.c > @@ -70,9 +70,12 @@ > #define PM_PFRAME(x) ((x) & PM_PFRAME_MASK) > > #define __PM_SOFT_DIRTY (1LL) > +#define __PM_MMAP_EXCLUSIVE (2LL) > #define PM_PRESENT PM_STATUS(4LL) > #define PM_SWAP PM_STATUS(2LL) > +#define PM_FILE PM_STATUS(1LL) > #define PM_SOFT_DIRTY __PM_PSHIFT(__PM_SOFT_DIRTY) > +#define PM_MMAP_EXCLUSIVE __PM_PSHIFT(__PM_MMAP_EXCLUSIVE) > > > /* > @@ -100,6 +103,8 @@ > #define KPF_SLOB_FREE 49 > #define KPF_SLUB_FROZEN 50 > #define KPF_SLUB_DEBUG 51 > +#define KPF_FILE 62 > +#define KPF_MMAP_EXCLUSIVE 63 > > #define KPF_ALL_BITS ((uint64_t)~0ULL) > #define KPF_HACKERS_BITS (0xffffULL << 32) > @@ -149,6 +154,9 @@ static const char * const page_flag_names[] = { > [KPF_SLOB_FREE] = "P:slob_free", > [KPF_SLUB_FROZEN] = "A:slub_frozen", > [KPF_SLUB_DEBUG] = "E:slub_debug", > + > + [KPF_FILE] = "F:file", > + [KPF_MMAP_EXCLUSIVE] = "1:mmap_exclusive", > }; > > > @@ -452,6 +460,10 @@ static uint64_t expand_overloaded_flags(uint64_t flags, uint64_t pme) > > if (pme & PM_SOFT_DIRTY) > flags |= BIT(SOFTDIRTY); > + if (pme & PM_FILE) > + flags |= BIT(FILE); > + if (pme & PM_MMAP_EXCLUSIVE) > + flags |= BIT(MMAP_EXCLUSIVE); > > return flags; > } > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>