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Date:      Wed, 15 Jul 2015 14:43:30 -0500
From:      Mark Felder <feld@FreeBSD.org>
To:        Sean Chittenden <seanc@groupon.com>, Adrian Gschwend <ml-ktk@netlabs.org>
Cc:        FreeBSD Filesystems <freebsd-fs@freebsd.org>
Subject:   Re: FreeBSD 10.1 Memory Exhaustion
Message-ID:  <1436989410.1427298.324703241.421E814B@webmail.messagingengine.com>
In-Reply-To: <CACfj5vJvAz9StvjTrA1TzfS%2BMhi_qSrOc_qBNHr8qXbiAj81xw@mail.gmail.com>
References:  <CAB2_NwCngPqFH4q-YZk00RO_aVF9JraeSsVX3xS0z5EV3YGa1Q@mail.gmail.com> <55A3A800.5060904@denninger.net> <55A4D5B7.2030603@freebsd.org> <55A4E5AB.8060909@netlabs.org> <CACfj5vJvAz9StvjTrA1TzfS%2BMhi_qSrOc_qBNHr8qXbiAj81xw@mail.gmail.com>

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On Tue, Jul 14, 2015, at 10:10, Sean Chittenden wrote:
> I think the reason this is not seen more often is because people
> frequently
> throw limits on the arc in /boot/loader.conf:
> 
> vfs.zfs.arc_min="18G"
> vfs.zfs.arc_max="149G"
> 
> ZFS ARC *should* not require those settings, but does currently for mixed
> workloads (i.e. databases) in order to be "stable".  By setting fixed
> sizes
> on the ARC, UMA and ARC are much more cooperative in that they have their
> own memory regions to manage so this behavior is not seen as often.
> 
> To be clear, however, it should not be necessary to set parameters like
> these in /boot/loader.conf in order to obtain consistent operational
> behavior.  I'd be curious to know if someone running 10.2 BETA without
> patches is able to trigger this behavior or not.  There was work done
> that
> reported helped with this between 10.1 and now.  To what extent it
> helped,
> however, I don't have any advice yet.
> 

I was about to email "I have 12TB at home and 4GB of RAM with a very
erratic workload and never run into any issues" and then I looked at
/boot/loader.conf and saw vfs.zfs.arc_max="2G"

Now I'm too scared to turn it off... :-)



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