ZEVO CE 1.1.1 tunables

Moderators: jhartley, MSR734, nola

ZEVO CE 1.1.1 tunables

Post by grahamperrin » Wed Nov 13, 2013 1:28 pm

I have begun experimenting with the tunables –

Code: Select all
sh-3.2$ sudo zdb -tune list
VARIABLE           VALUE     SOURCE
vdevmaxpending        10     default
vdevminpending         4     default
dmuprefetch            1     default
scrubprefetch          1     default


– with the understanding (from Ten's Complement beta testing) that they're for performance analysis only.

My current overrides (first experiment):

Code: Select all
gpes3e-gjp4:~ gjp22$ sudo zdb -tune list
VARIABLE           VALUE     SOURCE
vdevmaxpending         1     override
vdevminpending         1     override
dmuprefetch            0     override
scrubprefetch          0     override


Within the limitations of my MacBookPro5,2 (8 GB memory, single sshd used for both HFS Plus boot and ~500 GB ZFS home directory): early results are pleasing. There's the usual creep up to around thirty-three percent equity (reported by zstat), but the Mac feels much more responsive following login to that home, and during the period of creep. I'll probably not attempt to benchmark but so far, it certainly feels better.

Has anyone else experimented with the four tunables?

I'll be particularly interested to hear from people whose Macs are similarly constrained. Thanks.

Notes

Without overrides, zstat output 2013-05-12 03:46:49

With overrides, zstat output 2013-11-13 17:27:38

In the latter: no DMU zfetch measurement, and I guess that the misses for ARC prefetch data and ARC prefetch meta are negligible …

… I have a launch daemon that sets the tunables before I unlock the Core Storage logical volume for my ZFS home.

Related

ZEVO support topics include:


Elsewhere:

grahamperrin Offline

User avatar
 
Posts: 1596
Joined: Fri Sep 14, 2012 10:21 pm
Location: Brighton and Hove, United Kingdom

More good feeling from experiments with tunables

Post by grahamperrin » Thu Nov 14, 2013 3:59 pm

… early results are pleasing. … the Mac feels much more responsive following login … certainly feels better. …


This morning, a chance to see whether the overrides made a difference whilst Mountain Lion resumed various apps following a kernel panic.

In the screenshot below, after I booted, travelled to work then logged in:

  • swapfile1–swapfile7 (4.23 GB on disk) were created over a seven-minute period (shorter than expected)
  • the Mac felt much more responsive than expected.

2013-11-14 20-25-44 screenshot.png
2013-11-14 20-25-44 screenshot.png (125.49 KiB) Viewed 1940 times


For comparison, selected at random, part of a screenshot from two months ago (before I experimented with tunables):

without overrides.png
without overrides.png (105.74 KiB) Viewed 1940 times


It's not an ideal comparison, because in that September example I used a separate hard disk drive for swap, and so on. But the timing there – swapfile1–swapfile7 created over a forty-five minute period – is probably not unusual for my (heavy) use case.
grahamperrin Offline

User avatar
 
Posts: 1596
Joined: Fri Sep 14, 2012 10:21 pm
Location: Brighton and Hove, United Kingdom


Return to General Discussion

Who is online

Users browsing this forum: ilovezfs and 0 guests

cron