From: "Martin J. Bligh" <mbligh@aracnet.com>
To: Andrea Arcangeli <andrea@suse.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: -mmX 4G patches feedback [numbers: how much performance impact]
Date: Thu, 08 Apr 2004 15:19:51 -0700 [thread overview]
Message-ID: <29690000.1081462791@flay> (raw)
In-Reply-To: <20040408215946.GU31667@dualathlon.random>
--On Thursday, April 08, 2004 23:59:46 +0200 Andrea Arcangeli <andrea@suse.de> wrote:
> On Wed, Apr 07, 2004 at 11:24:16PM -0700, Martin J. Bligh wrote:
>> Instead of fiddling with tuning knobs, I'd prefer to just do the UKVA
>> idea I've proposed before, and let each process have their own pagetables
>> mapped permanently ;-)
>
> that will have you pay for pte-highmem even in non-highmem machines.
> I'm always been against your above idea ;) It can speedup mmap a bit for
> some uncommon case but I believe your slowdown comes from the page faults after
> exeve and startup not from mmap with the kernel compile, and worst of
> all for non-highmem too (no sysctl or tuning knob can save you then).
> Amittedly some mmap intensive workload can get a slight speedup compared
> to pte-highmem but I don't think it's common and it has the potential of
> slowing down the page faults especially in short lived tasks even w/o
> highmem.
You mean the page-faults for the pagetable mappings themselves? I wouldn't
have thought that'd make an impact - at least I don't see how it could be
worse than pte_highmem. And as we could make it conditional on highmem
anyway (or even CONFIG_64GB, I'm pretty sure 4GB machines don't need it),
I don't think it matters (ie you'd just turn it on instead of pte_highmem).
But you're right, we do need to take that into consideration.
> What I found attractive was the persistent kmap in userspace, but that
> idea breaks with threading, and Andrew found another way that is to make
> the page fault interruptible so it doesn't seem very worthwhile anymore
> even w/o threading.
Yeah, I've given up on that one ;-) The main use for it was pagetables
anyway, and we can do that without the threading problems.
M.
next prev parent reply other threads:[~2004-04-08 22:08 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-04-05 16:36 -mmX 4G patches feedback Eric Whiting
2004-04-05 17:46 ` Andrea Arcangeli
2004-04-05 21:35 ` Eric Whiting
2004-04-05 22:16 ` Andrea Arcangeli
2004-04-06 11:55 ` -mmX 4G patches feedback [numbers: how much performance impact] Ingo Molnar
2004-04-06 14:49 ` Eric Whiting
2004-04-06 15:59 ` Andrea Arcangeli
2004-04-06 16:13 ` Arjan van de Ven
2004-04-06 16:39 ` Andrea Arcangeli
2004-04-06 17:24 ` Ingo Molnar
2004-04-06 17:57 ` Andrea Arcangeli
2004-04-07 22:54 ` Martin J. Bligh
2004-04-07 22:50 ` Andrea Arcangeli
2004-04-06 19:25 ` Ingo Molnar
2004-04-06 20:25 ` Andrea Arcangeli
2004-04-07 6:03 ` Andrea Arcangeli
2004-04-07 6:46 ` Ingo Molnar
2004-04-07 7:23 ` Andrea Arcangeli
2004-04-07 8:23 ` Ingo Molnar
2004-04-07 21:35 ` Andrea Arcangeli
2004-04-07 17:27 ` Andrea Arcangeli
2004-04-07 7:25 ` Ingo Molnar
2004-04-07 21:39 ` Andrea Arcangeli
2004-04-07 22:58 ` Martin J. Bligh
2004-04-07 23:01 ` Andrea Arcangeli
2004-04-07 23:21 ` Martin J. Bligh
2004-04-07 23:18 ` Andrea Arcangeli
2004-04-07 23:34 ` Martin J. Bligh
2004-04-08 0:18 ` Andrea Arcangeli
2004-04-08 6:24 ` Martin J. Bligh
2004-04-08 21:59 ` Andrea Arcangeli
2004-04-08 22:19 ` Martin J. Bligh [this message]
2004-04-08 22:19 ` Andrea Arcangeli
2004-04-08 23:14 ` Martin J. Bligh
2004-04-08 23:22 ` Andrea Arcangeli
2004-04-08 23:42 ` Martin J. Bligh
2004-04-08 23:49 ` Andrea Arcangeli
2004-04-07 21:19 ` -mmX 4G patches feedback Martin J. Bligh
2004-04-07 21:49 ` Andrea Arcangeli
2004-04-06 17:59 -mmX 4G patches feedback [numbers: how much performance impact] Manfred Spraul
2004-04-06 18:41 ` Andrea Arcangeli
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