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Date:      Sun, 29 Oct 2023 00:42:14 +0200
From:      Guido Falsi <mad@madpilot.net>
To:        freebsd-stable@freebsd.org
Subject:   Re: periodic daily takes a very long time to run (14-stable)
Message-ID:  <b1b954a0-9698-4674-b8fd-02a2ab2c3e02@madpilot.net>
In-Reply-To: <ZT2MQGKLpMqDSunk@int21h>
References:  <ZTuNvVMW_XG3mZKU@int21h> <1122335317.4913.1698407124469@localhost> <ZTuyXPjddEPqh-bi@int21h> <794932758.6659.1698413675475@localhost> <ZTvMODY-mcBImHZP@int21h> <8a5c1f89eb5842f20e463c7d60538e598da3bc46.camel@gromit.dlib.vt.edu> <ZTvWSoCykzPzFKuw@int21h> <767774d4-50b5-47c8-9cf1-c0c99fe33e00@madpilot.net> <ZT2MQGKLpMqDSunk@int21h>

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On 29/10/23 00:33, void wrote:
> On Fri, Oct 27, 2023 at 05:38:58PM +0200, Guido Falsi wrote:
>> I have this for ccache FS (zfs):
>>
>> dumpster/ccache  atime                 on                     local
> 
> I wondered why you have this set to 'on'?
> 
> I mean I know /var/mail needs it for mail to function. Is it the same
> wiht ccache ?
> 

I used to have it off, but recently I turned it on. I have not really 
properly checked, but I have an hunch that ccache is using atime to 
decide which files to properly clean up the cache (LRU logic).

With atime - off you get atime = mtime, which is not the best option for 
LRU logic. You want objects to be counted as "hot" if they were 
created/modified a long time ago, but used yesterday.

Recent manual page does talk about atime, also a quick search in the 
sources reference atime multiple times. So it IS using it.

To be on the safe side, I've added this, but as I said I did this 
recently so I still don't know if it is really helping.

-- 
Guido Falsi <mad@madpilot.net>




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