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On Mon, 29 Mar 2010 10:43, Barry Pederson wrote:
In Message-Id: <4bb0bc7c.3000...@barryp.org>

I've been using the arc_summary.pl script from here:

http://jhell.googlecode.com/svn/base/head/scripts/zfs/arc_summary/arc_summary.pl

and noticed some odd numbers, with the ARC Current Size being larger than the Max Size, and the breakdown adding up to less than the current size as shown below

--------
ARC Size:
       Current Size:                           992.71M (arcsize)
       Target Size: (Adaptive)                 512.00M (c)
       Min Size (Hard Limit):                  81.82M (arc_min)
       Max Size (Hard Limit):                  512.00M (arc_max)

ARC Size Breakdown:
       Recently Used Cache Size:       99.84%  511.18M (p)
       Frequently Used Cache Size:     0.16%   0.82M (c-p)
--------


From another thread I saw, it sounds like arc_max isn't really
a "Hard Limit" but rather some kind of high water mark.  If that's
the case then I wonder if this might make more sense....



---------
--- arc_summary.pl.original     2010-02-25 19:23:13.000000000 -0600
+++ arc_summary.pl      2010-03-29 09:32:28.000000000 -0500
@@ -121,20 +121,20 @@

my $arc_size = ${Kstat}->{zfs}->{0}->{arcstats}->{size};
my $arc_size_MiB = ($arc_size / 1048576);
-my $mfu_size = $target_size - $mru_size;
+my $mfu_size = $arc_size - $mru_size;
my $mfu_size_MiB = ($mfu_size / 1048576);
-my $mru_perc = 100*($mru_size / $target_size);
-my $mfu_perc = 100*($mfu_size / $target_size);
+my $mru_perc = 100*($mru_size / $arc_size);
+my $mfu_perc = 100*($mfu_size / $arc_size);

print "ARC Size:\n";
printf("\tCurrent Size:\t\t\t\t%0.2fM (arcsize)\n", $arc_size_MiB);
printf("\tTarget Size: (Adaptive)\t\t\t%0.2fM (c)\n", $target_size_MiB);
printf("\tMin Size (Hard Limit):\t\t\t%0.2fM (arc_min)\n", $arc_min_size_MiB); -printf("\tMax Size (Hard Limit):\t\t\t%0.2fM (arc_max)\n", $arc_max_size_MiB); +printf("\tMax Size :\t\t\t%0.2fM (arc_max)\n", $arc_max_size_MiB);

print "\nARC Size Breakdown:\n";
printf("\tRecently Used Cache Size:\t%0.2f%%\t%0.2fM (p)\n", $mru_perc, $mru_size_MiB); -printf("\tFrequently Used Cache Size:\t%0.2f%%\t%0.2fM (c-p)\n", $mfu_perc, $mfu_size_MiB); +printf("\tFrequently Used Cache Size:\t%0.2f%%\t%0.2fM (arcsize-p)\n", $mfu_perc, $mfu_size_MiB);
print "\n";

### ARC Efficency ###

-----------


Giving something like this...

--------
ARC Size:
       Current Size:                           992.88M (arcsize)
       Target Size: (Adaptive)                 512.00M (c)
       Min Size (Hard Limit):                  81.82M (arc_min)
       Max Size             :                  512.00M (arc_max)

ARC Size Breakdown:
       Recently Used Cache Size:       51.48%  511.18M (p)
       Frequently Used Cache Size:     48.52%  481.70M (arcsize-p)
--------

        Barry


Barry,

What branch and revision was this run on ?

I need the above information because the output above just does not match up quite as it should and I want to investigate when, where & why as I believe something else is going on here that is not on the behalf of arc_summary.pl.

Or if you could provide me personally with the full output of the script from the downloads section "just to be sure" in an attachment that would work as well.

Thanks.

- --
 jhell

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