From: Laurent Dufour <ldufour@linux.vnet.ibm.com> To: Anshuman Khandual <khandual@linux.vnet.ibm.com>, Peter Zijlstra <peterz@infradead.org> Cc: "Kirill A. Shutemov" <kirill@shutemov.name>, paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org, ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox <willy@infradead.org>, benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, hpa@zytor.com, Will Deacon <will.deacon@arm.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, Tim Chen <tim.c.chen@linux.intel.com>, linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Date: Wed, 30 Aug 2017 11:53:41 +0200 [thread overview] Message-ID: <db7e5c3e-0bb6-a1f3-a025-379071c30183@linux.vnet.ibm.com> (raw) In-Reply-To: <ab0634c4-274d-208f-fc4b-43991986bacf@linux.vnet.ibm.com> On 30/08/2017 07:03, Anshuman Khandual wrote: > On 08/29/2017 07:15 PM, Peter Zijlstra wrote: >> On Tue, Aug 29, 2017 at 03:18:25PM +0200, Laurent Dufour wrote: >>> On 29/08/2017 14:04, Peter Zijlstra wrote: >>>> On Tue, Aug 29, 2017 at 09:59:30AM +0200, Laurent Dufour wrote: >>>>> On 27/08/2017 02:18, Kirill A. Shutemov wrote: >>>>>>> + >>>>>>> + if (unlikely(!vma->anon_vma)) >>>>>>> + goto unlock; >>>>>> >>>>>> It deserves a comment. >>>>> >>>>> You're right I'll add it in the next version. >>>>> For the record, the root cause is that __anon_vma_prepare() requires the >>>>> mmap_sem to be held because vm_next and vm_prev must be safe. >>>> >>>> But should that test not be: >>>> >>>> if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) >>>> goto unlock; >>>> >>>> Because !anon vmas will never have ->anon_vma set and you don't want to >>>> exclude those. >>> >>> Yes in the case we later allow non anonymous vmas to be handled. >>> Currently only anonymous vmas are supported so the check is good enough, >>> isn't it ? >> >> That wasn't at all clear from reading the code. This makes it clear >> ->anon_vma is only ever looked at for anonymous. >> >> And like Kirill says, we _really_ should start allowing some (if not >> all) vm_ops. Large file based mappings aren't particularly rare. >> >> I'm not sure we want to introduce a white-list or just bite the bullet >> and audit all ->fault() implementations. But either works and isn't >> terribly difficult, auditing all is more work though. > > filemap_fault() is used as vma-vm_ops->fault() for most of the file > systems. Changing it can enable speculative fault support for all of > them. It will still exclude other driver based vma-vm_ops->fault() > implementation. AFAICS, __lock_page_or_retry() function can drop > mm->mmap_sem if the page could not be locked right away. As suggested > by Peterz, making it understand FAULT_FLAG_SPECULATIVE should be good > enough. The patch is lightly tested for file mappings on top of this > series. Hi Anshuman, This sounds pretty good, except for the FAULT_FLAG_RETRY_NOWAIT's case I mentioned in another mail. The next step would be to find a way to discriminate between the vm_fault() functions. Any idea ? Thanks, Laurent. > > diff --git a/mm/filemap.c b/mm/filemap.c > index a497024..08f3042 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1181,6 +1181,18 @@ int __lock_page_killable(struct page *__page) > int __lock_page_or_retry(struct page *page, struct mm_struct *mm, > unsigned int flags) > { > + if (flags & FAULT_FLAG_SPECULATIVE) { > + if (flags & FAULT_FLAG_KILLABLE) { > + int ret; > + > + ret = __lock_page_killable(page); > + if (ret) > + return 0; > + } else > + __lock_page(page); > + return 1; > + } > + > if (flags & FAULT_FLAG_ALLOW_RETRY) { > /* > * CAUTION! In this case, mmap_sem is not released > diff --git a/mm/memory.c b/mm/memory.c > index 549d235..02347f3 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3836,8 +3836,6 @@ static int handle_pte_fault(struct vm_fault *vmf) > if (!vmf->pte) { > if (vma_is_anonymous(vmf->vma)) > return do_anonymous_page(vmf); > - else if (vmf->flags & FAULT_FLAG_SPECULATIVE) > - return VM_FAULT_RETRY; > else > return do_fault(vmf); > } > @@ -4012,17 +4010,7 @@ int handle_speculative_fault(struct mm_struct *mm, unsigned long address, > goto unlock; > } > > - /* > - * Can't call vm_ops service has we don't know what they would do > - * with the VMA. > - * This include huge page from hugetlbfs. > - */ > - if (vma->vm_ops) { > - trace_spf_vma_notsup(_RET_IP_, vma, address); > - goto unlock; > - } > - > - if (unlikely(!vma->anon_vma)) { > + if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) { > trace_spf_vma_notsup(_RET_IP_, vma, address); > goto unlock; > } >
WARNING: multiple messages have this Message-ID (diff)
From: Laurent Dufour <ldufour@linux.vnet.ibm.com> To: Anshuman Khandual <khandual@linux.vnet.ibm.com>, Peter Zijlstra <peterz@infradead.org> Cc: "Kirill A. Shutemov" <kirill@shutemov.name>, paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org, ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox <willy@infradead.org>, benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, hpa@zytor.com, Will Deacon <will.deacon@arm.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, Tim Chen <tim.c.chen@linux.intel.com>, linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Date: Wed, 30 Aug 2017 11:53:41 +0200 [thread overview] Message-ID: <db7e5c3e-0bb6-a1f3-a025-379071c30183@linux.vnet.ibm.com> (raw) In-Reply-To: <ab0634c4-274d-208f-fc4b-43991986bacf@linux.vnet.ibm.com> On 30/08/2017 07:03, Anshuman Khandual wrote: > On 08/29/2017 07:15 PM, Peter Zijlstra wrote: >> On Tue, Aug 29, 2017 at 03:18:25PM +0200, Laurent Dufour wrote: >>> On 29/08/2017 14:04, Peter Zijlstra wrote: >>>> On Tue, Aug 29, 2017 at 09:59:30AM +0200, Laurent Dufour wrote: >>>>> On 27/08/2017 02:18, Kirill A. Shutemov wrote: >>>>>>> + >>>>>>> + if (unlikely(!vma->anon_vma)) >>>>>>> + goto unlock; >>>>>> >>>>>> It deserves a comment. >>>>> >>>>> You're right I'll add it in the next version. >>>>> For the record, the root cause is that __anon_vma_prepare() requires the >>>>> mmap_sem to be held because vm_next and vm_prev must be safe. >>>> >>>> But should that test not be: >>>> >>>> if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) >>>> goto unlock; >>>> >>>> Because !anon vmas will never have ->anon_vma set and you don't want to >>>> exclude those. >>> >>> Yes in the case we later allow non anonymous vmas to be handled. >>> Currently only anonymous vmas are supported so the check is good enough, >>> isn't it ? >> >> That wasn't at all clear from reading the code. This makes it clear >> ->anon_vma is only ever looked at for anonymous. >> >> And like Kirill says, we _really_ should start allowing some (if not >> all) vm_ops. Large file based mappings aren't particularly rare. >> >> I'm not sure we want to introduce a white-list or just bite the bullet >> and audit all ->fault() implementations. But either works and isn't >> terribly difficult, auditing all is more work though. > > filemap_fault() is used as vma-vm_ops->fault() for most of the file > systems. Changing it can enable speculative fault support for all of > them. It will still exclude other driver based vma-vm_ops->fault() > implementation. AFAICS, __lock_page_or_retry() function can drop > mm->mmap_sem if the page could not be locked right away. As suggested > by Peterz, making it understand FAULT_FLAG_SPECULATIVE should be good > enough. The patch is lightly tested for file mappings on top of this > series. Hi Anshuman, This sounds pretty good, except for the FAULT_FLAG_RETRY_NOWAIT's case I mentioned in another mail. The next step would be to find a way to discriminate between the vm_fault() functions. Any idea ? Thanks, Laurent. > > diff --git a/mm/filemap.c b/mm/filemap.c > index a497024..08f3042 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1181,6 +1181,18 @@ int __lock_page_killable(struct page *__page) > int __lock_page_or_retry(struct page *page, struct mm_struct *mm, > unsigned int flags) > { > + if (flags & FAULT_FLAG_SPECULATIVE) { > + if (flags & FAULT_FLAG_KILLABLE) { > + int ret; > + > + ret = __lock_page_killable(page); > + if (ret) > + return 0; > + } else > + __lock_page(page); > + return 1; > + } > + > if (flags & FAULT_FLAG_ALLOW_RETRY) { > /* > * CAUTION! In this case, mmap_sem is not released > diff --git a/mm/memory.c b/mm/memory.c > index 549d235..02347f3 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3836,8 +3836,6 @@ static int handle_pte_fault(struct vm_fault *vmf) > if (!vmf->pte) { > if (vma_is_anonymous(vmf->vma)) > return do_anonymous_page(vmf); > - else if (vmf->flags & FAULT_FLAG_SPECULATIVE) > - return VM_FAULT_RETRY; > else > return do_fault(vmf); > } > @@ -4012,17 +4010,7 @@ int handle_speculative_fault(struct mm_struct *mm, unsigned long address, > goto unlock; > } > > - /* > - * Can't call vm_ops service has we don't know what they would do > - * with the VMA. > - * This include huge page from hugetlbfs. > - */ > - if (vma->vm_ops) { > - trace_spf_vma_notsup(_RET_IP_, vma, address); > - goto unlock; > - } > - > - if (unlikely(!vma->anon_vma)) { > + if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) { > trace_spf_vma_notsup(_RET_IP_, vma, address); > goto unlock; > } > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-08-30 9:53 UTC|newest] Thread overview: 122+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-08-17 22:04 [PATCH v2 00/20] Speculative page faults Laurent Dufour 2017-08-17 22:04 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 01/20] mm: Dont assume page-table invariance during faults Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 02/20] mm: Prepare for FAULT_FLAG_SPECULATIVE Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 03/20] mm: Introduce pte_spinlock " Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 04/20] mm: VMA sequence count Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 05/20] mm: Protect VMA modifications using " Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 06/20] mm: RCU free VMAs Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 07/20] mm: Cache some VMA fields in the vm_fault structure Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 08/20] mm: Protect SPF handler against anon_vma changes Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 09/20] mm/migrate: Pass vm_fault pointer to migrate_misplaced_page() Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 10/20] mm: Introduce __lru_cache_add_active_or_unevictable Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 11/20] mm: Introduce __maybe_mkwrite() Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 12/20] mm: Introduce __vm_normal_page() Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 13/20] mm: Introduce __page_add_new_anon_rmap() Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 14/20] mm: Provide speculative fault infrastructure Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-20 12:11 ` Sergey Senozhatsky 2017-08-20 12:11 ` Sergey Senozhatsky 2017-08-25 8:52 ` Laurent Dufour 2017-08-25 8:52 ` Laurent Dufour 2017-08-27 0:18 ` Kirill A. Shutemov 2017-08-27 0:18 ` Kirill A. Shutemov 2017-08-28 9:37 ` Peter Zijlstra 2017-08-28 9:37 ` Peter Zijlstra 2017-08-28 21:14 ` Benjamin Herrenschmidt 2017-08-28 21:14 ` Benjamin Herrenschmidt 2017-08-28 22:35 ` Andi Kleen 2017-08-28 22:35 ` Andi Kleen 2017-08-29 8:15 ` Peter Zijlstra 2017-08-29 8:15 ` Peter Zijlstra 2017-08-29 8:33 ` Peter Zijlstra 2017-08-29 8:33 ` Peter Zijlstra 2017-08-29 11:27 ` Peter Zijlstra 2017-08-29 11:27 ` Peter Zijlstra 2017-08-29 21:19 ` Benjamin Herrenschmidt 2017-08-29 21:19 ` Benjamin Herrenschmidt 2017-08-30 6:13 ` Peter Zijlstra 2017-08-30 6:13 ` Peter Zijlstra 2017-08-29 7:59 ` Laurent Dufour 2017-08-29 7:59 ` Laurent Dufour 2017-08-29 12:04 ` Peter Zijlstra 2017-08-29 12:04 ` Peter Zijlstra 2017-08-29 13:18 ` Laurent Dufour 2017-08-29 13:18 ` Laurent Dufour 2017-08-29 13:45 ` Peter Zijlstra 2017-08-29 13:45 ` Peter Zijlstra 2017-08-30 5:03 ` Anshuman Khandual 2017-08-30 5:03 ` Anshuman Khandual 2017-08-30 5:58 ` Peter Zijlstra 2017-08-30 5:58 ` Peter Zijlstra 2017-08-30 9:32 ` Laurent Dufour 2017-08-30 9:32 ` Laurent Dufour 2017-08-31 6:55 ` Anshuman Khandual 2017-08-31 6:55 ` Anshuman Khandual 2017-08-31 7:31 ` Peter Zijlstra 2017-08-31 7:31 ` Peter Zijlstra 2017-08-30 9:53 ` Laurent Dufour [this message] 2017-08-30 9:53 ` Laurent Dufour 2017-08-30 3:48 ` Anshuman Khandual 2017-08-30 3:48 ` Anshuman Khandual 2017-08-30 5:25 ` Anshuman Khandual 2017-08-30 5:25 ` Anshuman Khandual 2017-08-30 8:56 ` Laurent Dufour 2017-08-30 8:56 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 15/20] mm: Try spin lock in speculative path Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 16/20] mm: Adding speculative page fault failure trace events Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 17/20] perf: Add a speculative page fault sw event Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-21 8:55 ` Anshuman Khandual 2017-08-21 8:55 ` Anshuman Khandual 2017-08-22 1:46 ` Michael Ellerman 2017-08-22 1:46 ` Michael Ellerman 2017-08-17 22:05 ` [PATCH v2 18/20] perf tools: Add support for the SPF perf event Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-21 8:48 ` Anshuman Khandual 2017-08-21 8:48 ` Anshuman Khandual 2017-08-25 8:53 ` Laurent Dufour 2017-08-25 8:53 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 19/20] x86/mm: Add speculative pagefault handling Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-21 7:29 ` Anshuman Khandual 2017-08-21 7:29 ` Anshuman Khandual 2017-08-29 14:50 ` Laurent Dufour 2017-08-29 14:50 ` Laurent Dufour 2017-08-29 14:58 ` Laurent Dufour 2017-08-29 14:58 ` Laurent Dufour 2017-08-17 22:05 ` [PATCH v2 20/20] powerpc/mm: Add speculative page fault Laurent Dufour 2017-08-17 22:05 ` Laurent Dufour 2017-08-21 6:58 ` Anshuman Khandual 2017-08-21 6:58 ` Anshuman Khandual 2017-08-29 15:13 ` Laurent Dufour 2017-08-29 15:13 ` Laurent Dufour 2017-08-21 2:26 ` [PATCH v2 00/20] Speculative page faults Sergey Senozhatsky 2017-08-21 2:26 ` Sergey Senozhatsky 2017-09-08 9:24 ` Laurent Dufour 2017-09-08 9:24 ` Laurent Dufour 2017-09-11 0:45 ` Sergey Senozhatsky 2017-09-11 0:45 ` Sergey Senozhatsky 2017-09-11 6:28 ` Laurent Dufour 2017-09-11 6:28 ` Laurent Dufour 2017-08-21 6:28 ` Anshuman Khandual 2017-08-21 6:28 ` Anshuman Khandual 2017-08-22 0:41 ` Paul E. McKenney 2017-08-22 0:41 ` Paul E. McKenney 2017-08-25 9:41 ` Laurent Dufour 2017-08-25 9:41 ` Laurent Dufour
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