Re: WrMeta
Re: WrMeta
- Subject: Re: WrMeta
- From: Tilghman Lesher <email@hidden>
- Date: Sun, 08 Jul 2012 22:27:36 -0500
On Sun, Jul 8, 2012 at 9:03 PM, Chris Suter <email@hidden> wrote:
> Hi,
>
> On Sun, Jul 8, 2012 at 6:14 AM, Tilghman Lesher <email@hidden>
> wrote:
>>
>> On Fri, Jul 6, 2012 at 5:10 PM, Dave Keck <email@hidden> wrote:
>> >> Since this should be asynchronous, I'd be surprised if this is causing
>> >> a significant performance degradation...
>> >
>> > Thanks Shantonu! -- it was indeed updating the access time.
>> >
>> > Is there a supported way to prevent my process from updating the
>> > access time? My initial benchmarks show a 28% performance increase in
>> > processing 4000 photos (82 seconds before, 64 seconds after).
>>
>> Not your process, but you can at the filesystem mount level:
>> http://oroyphoto.com/2010/11/12/mac-os-x-noatime-settings-for-10-6/
>
>
> According to the Kernel sources, there’s something called “rapid aging” that
> might be relevant. Documentation is sparse so I don’t know its intended use,
> but it looks like something you can set per-process that will prevent access
> times from being set.
Per process or per thread, apparently. The usage is to call sysctl(3)
with KERN_RAGEVNODE and one of 4 magic values:
/* KERN_RAGEVNODE types */
#define KERN_RAGE_PROC 1
#define KERN_RAGE_THREAD 2
#define KERN_UNRAGE_PROC 3
#define KERN_UNRAGE_THREAD 4
The IOS documentation suggests that it's to be used only by background
tasks which request rapid aging, but other than that, I can find no
mention of the recommended way to ask for rapid aging. Comments in
the kernel also suggest that when an open vnode is accessed by a
"normal" process, rapid aging is turned off.
-Tilghman
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| References: | |
| | >WrMeta (From: Dave Keck <email@hidden>) |
| | >Re: WrMeta (From: Shantonu Sen <email@hidden>) |
| | >Re: WrMeta (From: Dave Keck <email@hidden>) |
| | >Re: WrMeta (From: Tilghman Lesher <email@hidden>) |
| | >Re: WrMeta (From: Chris Suter <email@hidden>) |