From: Nathan Zimmer <nzimmer@sgi.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Greg KH <gregkh@linuxfoundation.org>, <holt@sgi.com>,
<travis@sgi.com>, <rob@landley.net>, <tglx@linutronix.de>,
<mingo@redhat.com>, <yinghai@kernel.org>,
<akpm@linux-foundation.org>, <x86@kernel.org>,
<linux-doc@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [RFC 0/2] Delay initializing of large sections of memory
Date: Fri, 21 Jun 2013 12:18:21 -0500 [thread overview]
Message-ID: <51C48ADD.207@sgi.com> (raw)
In-Reply-To: <51C48745.9030304@zytor.com>
On 06/21/2013 12:03 PM, H. Peter Anvin wrote:
> On 06/21/2013 09:51 AM, Greg KH wrote:
>> On Fri, Jun 21, 2013 at 11:25:32AM -0500, Nathan Zimmer wrote:
>>> This rfc patch set delays initializing large sections of memory until we have
>>> started cpus. This has the effect of reducing startup times on large memory
>>> systems. On 16TB it can take over an hour to boot and most of that time
>>> is spent initializing memory.
>>>
>>> We avoid that bottleneck by delaying initialization until after we have
>>> started multiple cpus and can initialize in a multithreaded manner.
>>> This allows us to actually reduce boot time rather then just moving around
>>> the point of initialization.
>>>
>>> Mike and I have worked on this set for a while, with him doing the most of the
>>> heavy lifting, and are eager for some feedback.
>> Why make this a config option at all, why not just always do this if the
>> memory size is larger than some specific number (like 8TB?)
>>
>> Otherwise the distros will always enable this option, and having it be a
>> configuration choice doesn't make any sense.
>>
> Since you made it a compile time option, it would be good to know how
> much code it adds, but otherwise I agree with Greg here... this really
> shouldn't need to be an option. It *especially* shouldn't need to be a
> hand-set runtime option (which looks quite complex, to boot.)
The patchset as a whole is just over 400 lines so it doesn't add alot.
If I were to pull the .config option it would probably remove 30 lines.
The command line option is too complex but some of the data I haven't
found a way
to get at runtime yet.
>
> I suspect the cutoff for this should be a lot lower than 8 TB even, more
> like 128 GB or so. The only concern is to not set the cutoff so low
> that we can end up running out of memory or with suboptimal NUMA
> placement just because of this.
Even at lower amounts of ram there is an positive impact.I it knocks
time off
boot even at as small as a 1TB of ram.
> Also, in case it is not bloody obvious: whatever memory the kernel image
> was loaded into MUST be considered "online", even if it is loaded way high.
>
> -hpa
>
>
>
>
Ok
next prev parent reply other threads:[~2013-06-21 17:18 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-21 16:25 [RFC 0/2] Delay initializing of large sections of memory Nathan Zimmer
2013-06-21 16:25 ` [RFC 1/2] x86_64, mm: Delay initializing large portion " Nathan Zimmer
2013-06-25 4:14 ` Rob Landley
2013-06-21 16:25 ` [RFC 2/2] x86_64, mm: Reinsert the absent memory Nathan Zimmer
2013-06-23 9:28 ` Ingo Molnar
2013-06-23 9:32 ` Ingo Molnar
2013-06-24 17:38 ` H. Peter Anvin
2013-06-24 19:39 ` Ingo Molnar
2013-06-24 20:08 ` H. Peter Anvin
2013-06-25 7:31 ` Ingo Molnar
2013-06-24 20:36 ` Nathan Zimmer
2013-06-25 7:38 ` Ingo Molnar
2013-06-25 15:07 ` H. Peter Anvin
2013-06-25 17:19 ` Mike Travis
2013-06-25 17:22 ` Mike Travis
2013-06-25 18:43 ` H. Peter Anvin
2013-06-25 18:51 ` Mike Travis
2013-06-26 9:22 ` [RFC] Transparent on-demand memory setup initialization embedded in the (GFP) buddy allocator Ingo Molnar
2013-06-26 13:28 ` Andrew Morton
2013-06-26 13:37 ` Ingo Molnar
2013-06-26 15:02 ` Nathan Zimmer
2013-06-26 16:15 ` Mike Travis
2013-06-26 12:14 ` [RFC 2/2] x86_64, mm: Reinsert the absent memory Ingo Molnar
2013-06-26 14:49 ` Nathan Zimmer
2013-06-26 15:12 ` Dave Hansen
2013-06-26 15:20 ` Nathan Zimmer
2013-06-26 15:58 ` Ingo Molnar
2013-06-26 16:11 ` Nathan Zimmer
2013-06-26 16:07 ` Mike Travis
2013-06-21 16:51 ` [RFC 0/2] Delay initializing of large sections of memory Greg KH
2013-06-21 17:03 ` H. Peter Anvin
2013-06-21 17:18 ` Nathan Zimmer [this message]
2013-06-21 17:28 ` H. Peter Anvin
2013-06-21 20:05 ` Nathan Zimmer
2013-06-21 20:08 ` H. Peter Anvin
2013-06-21 20:33 ` Nathan Zimmer
2013-06-21 21:36 ` Mike Travis
2013-06-21 21:07 ` Mike Travis
2013-06-21 18:44 ` Yinghai Lu
2013-06-21 18:50 ` Greg KH
2013-06-21 19:10 ` Yinghai Lu
2013-06-21 19:19 ` Nathan Zimmer
2013-06-21 20:28 ` Yinghai Lu
2013-06-21 20:40 ` Nathan Zimmer
2013-06-21 21:30 ` Mike Travis
2013-06-22 0:23 ` Yinghai Lu
2013-06-25 17:35 ` Mike Travis
2013-06-25 18:17 ` H. Peter Anvin
2013-06-25 18:40 ` Mike Travis
2013-06-25 18:40 ` Yinghai Lu
2013-06-25 18:44 ` H. Peter Anvin
2013-06-25 18:58 ` Mike Travis
2013-06-25 19:03 ` Yinghai Lu
2013-06-25 19:09 ` H. Peter Anvin
2013-06-25 19:28 ` Yinghai Lu
2013-06-27 6:37 ` Yinghai Lu
2013-06-27 11:05 ` Robin Holt
2013-06-27 15:50 ` Mike Travis
2013-06-26 9:23 ` Ingo Molnar
2013-06-25 18:38 ` Yinghai Lu
2013-06-25 18:42 ` Mike Travis
2013-06-21 18:36 ` Yinghai Lu
2013-06-21 18:44 ` Greg Kroah-Hartman
2013-06-21 19:00 ` Yinghai Lu
2013-06-21 21:28 ` Mike Travis
2013-06-21 21:19 ` Mike Travis
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