| Message ID | 1482506098-6149-1-git-send-email-minchan@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat 24-12-16 00:14:58, Minchan Kim wrote: > Andreas reported [1] made a test in jemalloc hang in THP mode in arm64. > http://lkml.kernel.org/r/mvmmvfy37g1.fsf@hawking.suse.de > > The problem is currently page fault handler doesn't supports dirty bit > emulation of pmd for non-HW dirty-bit architecture so that application > stucks until VM marked the pmd dirty. > > How the emulation work depends on the architecture. In case of arm64, > when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to > mark the pte dirty via triggering page fault when store access happens. > Once the page fault occurs, VM marks the pmd dirty and arch code for > setting pmd will clear PTE_RDONLY for application to proceed. > > IOW, if VM doesn't mark the pmd dirty, application hangs forever by > repeated fault(i.e., store op but the pmd is PTE_RDONLY). > > This patch enables pmd dirty-bit emulation for those architectures. Thanks for extending the patch description again! > [1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called > > Cc: Jason Evans <je@fb.com> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: linux-arch@vger.kernel.org > Cc: linux-arm-kernel@lists.infradead.org > Cc: <stable@vger.kernel.org> [4.5+] > Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called") > Reported-and-Tested-by: Andreas Schwab <schwab@suse.de> > Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Signed-off-by: Minchan Kim <minchan@kernel.org> Acked-by: Michal Hocko <mhocko@suse.com> > --- > Merry Xmas! > > * from v3 > * Elaborate description > * from v2 > * Add acked-by/tested-by > * from v1 > * Remove __handle_mm_fault part - Kirill > mm/huge_memory.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 10eedbf..29ec8a4 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) > { > pmd_t entry; > unsigned long haddr; > + bool write = vmf->flags & FAULT_FLAG_WRITE; > > vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); > if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) > goto unlock; > > entry = pmd_mkyoung(orig_pmd); > + if (write) > + entry = pmd_mkdirty(entry); > haddr = vmf->address & HPAGE_PMD_MASK; > - if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, > - vmf->flags & FAULT_FLAG_WRITE)) > + if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write)) > update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd); > > unlock: > -- > 2.7.4 >
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 10eedbf..29ec8a4 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) { pmd_t entry; unsigned long haddr; + bool write = vmf->flags & FAULT_FLAG_WRITE; vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) goto unlock; entry = pmd_mkyoung(orig_pmd); + if (write) + entry = pmd_mkdirty(entry); haddr = vmf->address & HPAGE_PMD_MASK; - if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, - vmf->flags & FAULT_FLAG_WRITE)) + if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write)) update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd); unlock:
Andreas reported [1] made a test in jemalloc hang in THP mode in arm64. http://lkml.kernel.org/r/mvmmvfy37g1.fsf@hawking.suse.de The problem is currently page fault handler doesn't supports dirty bit emulation of pmd for non-HW dirty-bit architecture so that application stucks until VM marked the pmd dirty. How the emulation work depends on the architecture. In case of arm64, when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to mark the pte dirty via triggering page fault when store access happens. Once the page fault occurs, VM marks the pmd dirty and arch code for setting pmd will clear PTE_RDONLY for application to proceed. IOW, if VM doesn't mark the pmd dirty, application hangs forever by repeated fault(i.e., store op but the pmd is PTE_RDONLY). This patch enables pmd dirty-bit emulation for those architectures. [1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called Cc: Jason Evans <je@fb.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: linux-arch@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: <stable@vger.kernel.org> [4.5+] Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called") Reported-and-Tested-by: Andreas Schwab <schwab@suse.de> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Minchan Kim <minchan@kernel.org> --- Merry Xmas! * from v3 * Elaborate description * from v2 * Add acked-by/tested-by * from v1 * Remove __handle_mm_fault part - Kirill mm/huge_memory.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)