| Message ID | 1374742461-29160-2-git-send-email-schwidefsky@de.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 25/07/13 10:54, Martin Schwidefsky wrote: > From: Konstantin Weitz <konstantin.weitz@gmail.com> > > In a virtualized environment and given an appropriate interface the guest > can mark pages as unused while they are free (for the s390 implementation > see git commit 45e576b1c3d00206 "guest page hinting light"). For the host > the unused state is a property of the pte. > > This patch adds the primitive 'pte_unused' and code to the host swap out > handler so that pages marked as unused by all mappers are not swapped out > but discarded instead, thus saving one IO for swap out and potentially > another one for swap in. > > [ Martin Schwidefsky: patch reordering and simplification ] > > Signed-off-by: Konstantin Weitz <konstantin.weitz@gmail.com> > Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> > --- > include/asm-generic/pgtable.h | 13 +++++++++++++ > mm/rmap.c | 10 ++++++++++ > 2 files changed, 23 insertions(+) > > diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h > index 2f47ade..ec540c5 100644 > --- a/include/asm-generic/pgtable.h > +++ b/include/asm-generic/pgtable.h > @@ -193,6 +193,19 @@ static inline int pte_same(pte_t pte_a, pte_t pte_b) > } > #endif > > +#ifndef __HAVE_ARCH_PTE_UNUSED > +/* > + * Some architectures provide facilities to virtualization guests > + * so that they can flag allocated pages as unused. This allows the > + * host to transparently reclaim unused pages. This function returns > + * whether the pte's page is unused. > + */ > +static inline int pte_unused(pte_t pte) > +{ > + return 0; > +} > +#endif > + > #ifndef __HAVE_ARCH_PMD_SAME > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b) > diff --git a/mm/rmap.c b/mm/rmap.c > index cd356df..2291f25 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1234,6 +1234,16 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > } > set_pte_at(mm, address, pte, > swp_entry_to_pte(make_hwpoison_entry(page))); > + } else if (pte_unused(pteval)) { > + /* > + * The guest indicated that the page content is of no > + * interest anymore. Simply discard the pte, vmscan > + * will take care of the rest. > + */ > + if (PageAnon(page)) > + dec_mm_counter(mm, MM_ANONPAGES); > + else > + dec_mm_counter(mm, MM_FILEPAGES); > } else if (PageAnon(page)) { > swp_entry_t entry = { .val = page_private(page) }; > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, 25 Jul 2013 10:54:20 +0200 Martin Schwidefsky <schwidefsky@de.ibm.com> wrote: > From: Konstantin Weitz <konstantin.weitz@gmail.com> > > In a virtualized environment and given an appropriate interface the guest > can mark pages as unused while they are free (for the s390 implementation > see git commit 45e576b1c3d00206 "guest page hinting light"). For the host > the unused state is a property of the pte. > > This patch adds the primitive 'pte_unused' and code to the host swap out > handler so that pages marked as unused by all mappers are not swapped out > but discarded instead, thus saving one IO for swap out and potentially > another one for swap in. > > ... > > --- a/include/asm-generic/pgtable.h > +++ b/include/asm-generic/pgtable.h > @@ -193,6 +193,19 @@ static inline int pte_same(pte_t pte_a, pte_t pte_b) > } > #endif > > +#ifndef __HAVE_ARCH_PTE_UNUSED > +/* > + * Some architectures provide facilities to virtualization guests > + * so that they can flag allocated pages as unused. This allows the > + * host to transparently reclaim unused pages. This function returns > + * whether the pte's page is unused. > + */ > +static inline int pte_unused(pte_t pte) > +{ > + return 0; > +} > +#endif > + > #ifndef __HAVE_ARCH_PMD_SAME > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b) > diff --git a/mm/rmap.c b/mm/rmap.c > index cd356df..2291f25 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1234,6 +1234,16 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > } > set_pte_at(mm, address, pte, > swp_entry_to_pte(make_hwpoison_entry(page))); > + } else if (pte_unused(pteval)) { > + /* > + * The guest indicated that the page content is of no > + * interest anymore. Simply discard the pte, vmscan > + * will take care of the rest. > + */ > + if (PageAnon(page)) > + dec_mm_counter(mm, MM_ANONPAGES); > + else > + dec_mm_counter(mm, MM_FILEPAGES); > } else if (PageAnon(page)) { > swp_entry_t entry = { .val = page_private(page) }; Obviously harmless. Please include this in whatever tree carries "[PATCH 2/2] s390/kvm: support collaborative memory management". -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, 30 Jul 2013 13:44:22 -0700 Andrew Morton <akpm@linux-foundation.org> wrote: > On Thu, 25 Jul 2013 10:54:20 +0200 Martin Schwidefsky <schwidefsky@de.ibm.com> wrote: > > > From: Konstantin Weitz <konstantin.weitz@gmail.com> > > > > In a virtualized environment and given an appropriate interface the guest > > can mark pages as unused while they are free (for the s390 implementation > > see git commit 45e576b1c3d00206 "guest page hinting light"). For the host > > the unused state is a property of the pte. > > > > This patch adds the primitive 'pte_unused' and code to the host swap out > > handler so that pages marked as unused by all mappers are not swapped out > > but discarded instead, thus saving one IO for swap out and potentially > > another one for swap in. > > > > ... > > > > --- a/include/asm-generic/pgtable.h > > +++ b/include/asm-generic/pgtable.h > > @@ -193,6 +193,19 @@ static inline int pte_same(pte_t pte_a, pte_t pte_b) > > } > > #endif > > > > +#ifndef __HAVE_ARCH_PTE_UNUSED > > +/* > > + * Some architectures provide facilities to virtualization guests > > + * so that they can flag allocated pages as unused. This allows the > > + * host to transparently reclaim unused pages. This function returns > > + * whether the pte's page is unused. > > + */ > > +static inline int pte_unused(pte_t pte) > > +{ > > + return 0; > > +} > > +#endif > > + > > #ifndef __HAVE_ARCH_PMD_SAME > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > > static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b) > > diff --git a/mm/rmap.c b/mm/rmap.c > > index cd356df..2291f25 100644 > > --- a/mm/rmap.c > > +++ b/mm/rmap.c > > @@ -1234,6 +1234,16 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > > } > > set_pte_at(mm, address, pte, > > swp_entry_to_pte(make_hwpoison_entry(page))); > > + } else if (pte_unused(pteval)) { > > + /* > > + * The guest indicated that the page content is of no > > + * interest anymore. Simply discard the pte, vmscan > > + * will take care of the rest. > > + */ > > + if (PageAnon(page)) > > + dec_mm_counter(mm, MM_ANONPAGES); > > + else > > + dec_mm_counter(mm, MM_FILEPAGES); > > } else if (PageAnon(page)) { > > swp_entry_t entry = { .val = page_private(page) }; > > Obviously harmless. Please include this in whatever tree carries > "[PATCH 2/2] s390/kvm: support collaborative memory management". Cool, thanks. This will go out via the KVM tree then.
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index 2f47ade..ec540c5 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -193,6 +193,19 @@ static inline int pte_same(pte_t pte_a, pte_t pte_b) } #endif +#ifndef __HAVE_ARCH_PTE_UNUSED +/* + * Some architectures provide facilities to virtualization guests + * so that they can flag allocated pages as unused. This allows the + * host to transparently reclaim unused pages. This function returns + * whether the pte's page is unused. + */ +static inline int pte_unused(pte_t pte) +{ + return 0; +} +#endif + #ifndef __HAVE_ARCH_PMD_SAME #ifdef CONFIG_TRANSPARENT_HUGEPAGE static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b) diff --git a/mm/rmap.c b/mm/rmap.c index cd356df..2291f25 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1234,6 +1234,16 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, } set_pte_at(mm, address, pte, swp_entry_to_pte(make_hwpoison_entry(page))); + } else if (pte_unused(pteval)) { + /* + * The guest indicated that the page content is of no + * interest anymore. Simply discard the pte, vmscan + * will take care of the rest. + */ + if (PageAnon(page)) + dec_mm_counter(mm, MM_ANONPAGES); + else + dec_mm_counter(mm, MM_FILEPAGES); } else if (PageAnon(page)) { swp_entry_t entry = { .val = page_private(page) };