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From: Hugh Dickins <hugh@veritas.com>
To: "Martin J. Bligh" <mbligh@mbligh.org>
Cc: Arjan van de Ven <arjan@infradead.org>,
	Dave McCracken <dmccr@us.ibm.com>, Andrew Morton <akpm@osdl.org>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Linux Memory Management <linux-mm@kvack.org>
Subject: Re: [PATCH 1/1] Implement shared page tables
Date: Wed, 31 Aug 2005 16:06:12 +0100 (BST)	[thread overview]
Message-ID: <Pine.LNX.4.61.0508311557190.17726@goblin.wat.veritas.com> (raw)
In-Reply-To: <16640000.1125498711@[10.10.2.4]>

On Wed, 31 Aug 2005, Martin J. Bligh wrote:
> --Hugh Dickins <hugh@veritas.com> wrote (on Wednesday, August 31, 2005 14:42:38 +0100):
> > 
> > Which is indeed a further disincentive against shared page tables.
> 
> Or shared pagetables a disincentive to randomizing the mmap space ;-)

Fair point!

> They're incompatible, but you could be left to choose one or the other
> via config option.

Wouldn't need config option: there's /proc/sys/kernel/randomize_va_space
for the whole running system, compatibility check on the ELFs run, and
the infinite stack rlimit: enough ways to suppress randomization if it
doesn't suit you.

> 3% on "a certain industry-standard database benchmark" (cough) is huge,
> and we expect the benefit for PPC64 will be larger as we can share the
> underlying hardware PTEs without TLB flushing as well.

Okay - and you're implying that 3% comes from _using_ the shared page
tables, rather than from avoiding the fork/exit overhead of setting
them up and tearing them down.  And it can't use huge TLB pages
because...  fragmentation?

Hugh

  parent reply	other threads:[~2005-08-31 15:04 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-08-30 22:13 [PATCH 1/1] Implement shared page tables Dave McCracken
2005-08-31 11:44 ` Hugh Dickins
2005-08-31 11:51   ` Arjan van de Ven
2005-08-31 13:42     ` Hugh Dickins
2005-08-31 14:31       ` Martin J. Bligh
2005-08-31 14:41         ` Arjan van de Ven
2005-08-31 15:06         ` Hugh Dickins [this message]
2005-08-31 15:39           ` Martin J. Bligh
2005-08-31 16:40   ` Dave McCracken
2005-09-02  1:58 ` Chen, Kenneth W
2005-09-02 16:40   ` Dave McCracken
2005-09-02  4:26 ` Chen, Kenneth W

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