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From: Cyrill Gorcunov <gorcunov@gmail.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>,
	Peter Feiner <pfeiner@google.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Pavel Emelyanov <xemul@parallels.com>,
	Jamie Liu <jamieliu@google.com>,
	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Magnus Damm <magnus.damm@gmail.com>
Subject: Re: [PATCH v5] mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared
Date: Tue, 26 Aug 2014 19:53:51 +0400	[thread overview]
Message-ID: <20140826155351.GC8952@moon> (raw)
In-Reply-To: <20140826154355.GA11464@node.dhcp.inet.fi>

On Tue, Aug 26, 2014 at 06:43:55PM +0300, Kirill A. Shutemov wrote:
> On Tue, Aug 26, 2014 at 07:18:13PM +0400, Cyrill Gorcunov wrote:
> > > Basically, it's safe if only soft-dirty is allowed to modify vm_flags
> > > without down_write(). But why is soft-dirty so special?
> > 
> > because how we use this bit, i mean in normal workload this bit won't
> > be used intensively i think so it's not widespread in kernel code
> 
> Weak argument to me.
> 
> What about walk through vmas twice: first with down_write() to modify
> vm_flags and vm_page_prot, then downgrade_write() and do
> walk_page_range() on every vma?

I still it's undeeded, but for sure using write-lock/downgrade won't hurt,
so no argues from my side.

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WARNING: multiple messages have this Message-ID (diff)
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>,
	Peter Feiner <pfeiner@google.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Pavel Emelyanov <xemul@parallels.com>,
	Jamie Liu <jamieliu@google.com>,
	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Magnus Damm <magnus.damm@gmail.com>
Subject: Re: [PATCH v5] mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared
Date: Tue, 26 Aug 2014 19:53:51 +0400	[thread overview]
Message-ID: <20140826155351.GC8952@moon> (raw)
In-Reply-To: <20140826154355.GA11464@node.dhcp.inet.fi>

On Tue, Aug 26, 2014 at 06:43:55PM +0300, Kirill A. Shutemov wrote:
> On Tue, Aug 26, 2014 at 07:18:13PM +0400, Cyrill Gorcunov wrote:
> > > Basically, it's safe if only soft-dirty is allowed to modify vm_flags
> > > without down_write(). But why is soft-dirty so special?
> > 
> > because how we use this bit, i mean in normal workload this bit won't
> > be used intensively i think so it's not widespread in kernel code
> 
> Weak argument to me.
> 
> What about walk through vmas twice: first with down_write() to modify
> vm_flags and vm_page_prot, then downgrade_write() and do
> walk_page_range() on every vma?

I still it's undeeded, but for sure using write-lock/downgrade won't hurt,
so no argues from my side.

  reply	other threads:[~2014-08-26 15:53 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
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 [this message]
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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