From: Peter Feiner <pfeiner@google.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Pavel Emelyanov <xemul@parallels.com>,
Jamie Liu <jamieliu@google.com>, Hugh Dickins <hughd@google.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Andrew Morton <akpm@linux-foundation.org>,
Magnus Damm <damm@opensource.se>
Subject: Re: [PATCH] mm: softdirty: write protect PTEs created for read faults after VM_SOFTDIRTY cleared
Date: Thu, 21 Aug 2014 18:50:33 -0400 [thread overview]
Message-ID: <20140821225033.GE16042@google.com> (raw)
In-Reply-To: <20140821215147.GA15482@node.dhcp.inet.fi>
On Fri, Aug 22, 2014 at 12:51:47AM +0300, Kirill A. Shutemov wrote:
> > > One thing: there could be (I haven't checked) complications on
> > > vma_merge(): since vm_flags are identical it assumes that it can reuse
> > > vma->vm_page_prot of expanded vma. But VM_SOFTDIRTY is excluded from
> > > vm_flags compatibility check. What should we do with vm_page_prot there?
> >
> > Since the merged VMA will have VM_SOFTDIRTY set, it's OK that it's vm_page_prot
> > won't be setup for write notifications. For the purpose of process migration,
> > you'll just get some false positives, which is tolerable.
>
> Right. But should we disable writenotify back to avoid exessive wp-faults
> if it was enabled due to soft-dirty (the case when expanded vma is
> soft-dirty)?
Ah, I understand now. I've got a patch in the works that disables the write
faults when a VMA is merged. I'll send a series with all of the changes
tomorrow.
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WARNING: multiple messages have this Message-ID (diff)
From: Peter Feiner <pfeiner@google.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Pavel Emelyanov <xemul@parallels.com>,
Jamie Liu <jamieliu@google.com>, Hugh Dickins <hughd@google.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Andrew Morton <akpm@linux-foundation.org>,
Magnus Damm <damm@opensource.se>
Subject: Re: [PATCH] mm: softdirty: write protect PTEs created for read faults after VM_SOFTDIRTY cleared
Date: Thu, 21 Aug 2014 18:50:33 -0400 [thread overview]
Message-ID: <20140821225033.GE16042@google.com> (raw)
In-Reply-To: <20140821215147.GA15482@node.dhcp.inet.fi>
On Fri, Aug 22, 2014 at 12:51:47AM +0300, Kirill A. Shutemov wrote:
> > > One thing: there could be (I haven't checked) complications on
> > > vma_merge(): since vm_flags are identical it assumes that it can reuse
> > > vma->vm_page_prot of expanded vma. But VM_SOFTDIRTY is excluded from
> > > vm_flags compatibility check. What should we do with vm_page_prot there?
> >
> > Since the merged VMA will have VM_SOFTDIRTY set, it's OK that it's vm_page_prot
> > won't be setup for write notifications. For the purpose of process migration,
> > you'll just get some false positives, which is tolerable.
>
> Right. But should we disable writenotify back to avoid exessive wp-faults
> if it was enabled due to soft-dirty (the case when expanded vma is
> soft-dirty)?
Ah, I understand now. I've got a patch in the works that disables the write
faults when a VMA is merged. I'll send a series with all of the changes
tomorrow.
next prev parent reply other threads:[~2014-08-21 22:50 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-20 21:46 [PATCH] mm: softdirty: write protect PTEs created for read faults after VM_SOFTDIRTY cleared Peter Feiner
2014-08-20 21:46 ` Peter Feiner
2014-08-20 23:45 ` Kirill A. Shutemov
2014-08-20 23:45 ` Kirill A. Shutemov
2014-08-21 19:37 ` Peter Feiner
2014-08-21 19:37 ` Peter Feiner
2014-08-21 20:51 ` Cyrill Gorcunov
2014-08-21 20:51 ` Cyrill Gorcunov
2014-08-21 21:39 ` Kirill A. Shutemov
2014-08-21 21:39 ` Kirill A. Shutemov
2014-08-21 21:46 ` Peter Feiner
2014-08-21 21:46 ` Peter Feiner
2014-08-21 21:51 ` Kirill A. Shutemov
2014-08-21 21:51 ` Kirill A. Shutemov
2014-08-21 22:50 ` Peter Feiner [this message]
2014-08-21 22:50 ` Peter Feiner
2014-08-22 6:33 ` Cyrill Gorcunov
2014-08-22 6:33 ` Cyrill Gorcunov
2014-08-23 22:11 ` [PATCH v2 0/3] softdirty fix and write notification cleanup Peter Feiner
2014-08-23 22:11 ` Peter Feiner
2014-08-23 22:11 ` [PATCH v2 1/3] mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared Peter Feiner
2014-08-23 22:11 ` Peter Feiner
2014-08-23 23:00 ` Kirill A. Shutemov
2014-08-23 23:00 ` Kirill A. Shutemov
2014-08-23 23:15 ` Peter Feiner
2014-08-23 23:15 ` Peter Feiner
2014-08-23 23:50 ` Kirill A. Shutemov
2014-08-23 23:50 ` Kirill A. Shutemov
2014-08-24 0:55 ` Peter Feiner
2014-08-24 0:55 ` Peter Feiner
2014-08-23 22:12 ` [PATCH v2 2/3] mm: mprotect: preserve special page protection bits Peter Feiner
2014-08-23 22:12 ` Peter Feiner
2014-08-23 22:12 ` [PATCH v2 3/3] mm: mmap: cleanup code that preserves special vm_page_prot bits Peter Feiner
2014-08-23 22:12 ` Peter Feiner
2014-08-24 1:43 ` [PATCH v3] mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared Peter Feiner
2014-08-24 1:43 ` Peter Feiner
2014-08-24 7:59 ` Kirill A. Shutemov
2014-08-24 7:59 ` Kirill A. Shutemov
2014-08-24 19:22 ` Cyrill Gorcunov
2014-08-24 19:22 ` Cyrill Gorcunov
2014-08-24 14:41 ` [PATCH v4] " Peter Feiner
2014-08-24 14:41 ` Peter Feiner
2014-08-25 3:34 ` [PATCH v5] " Peter Feiner
2014-08-25 3:34 ` Peter Feiner
2014-08-26 4:45 ` Hugh Dickins
2014-08-26 4:45 ` Hugh Dickins
2014-08-26 6:49 ` Cyrill Gorcunov
2014-08-26 6:49 ` Cyrill Gorcunov
2014-08-26 14:04 ` Kirill A. Shutemov
2014-08-26 14:04 ` Kirill A. Shutemov
2014-08-26 14:19 ` Cyrill Gorcunov
2014-08-26 14:19 ` Cyrill Gorcunov
2014-08-26 14:56 ` Kirill A. Shutemov
2014-08-26 14:56 ` Kirill A. Shutemov
2014-08-26 15:18 ` Cyrill Gorcunov
2014-08-26 15:18 ` Cyrill Gorcunov
2014-08-26 15:43 ` Kirill A. Shutemov
2014-08-26 15:43 ` Kirill A. Shutemov
2014-08-26 15:53 ` Cyrill Gorcunov
2014-08-26 15:53 ` Cyrill Gorcunov
2014-08-27 23:12 ` Hugh Dickins
2014-08-27 23:12 ` Hugh Dickins
2014-08-28 6:31 ` Cyrill Gorcunov
2014-08-28 6:31 ` Cyrill Gorcunov
2014-08-27 21:55 ` Hugh Dickins
2014-08-27 21:55 ` Hugh Dickins
2014-09-04 16:43 ` Peter Feiner
2014-09-04 16:43 ` Peter Feiner
2014-09-07 21:31 ` Peter Feiner
2014-09-07 21:31 ` Peter Feiner
2014-09-07 23:01 ` [PATCH v6] " Peter Feiner
2014-09-07 23:01 ` Peter Feiner
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