Date: Mon, 29 Mar 2010 09:43:08 -0500 From: Barry Pederson <bp@barryp.org> To: jhell <jhell@DataIX.net> Cc: FreeBSD Stable <freebsd-stable@freebsd.org> Subject: ZFS Tuning - arc_summary.pl Message-ID: <4BB0BC7C.3000801@barryp.org> In-Reply-To: <alpine.BSF.2.00.1002170321200.14189@pragry.qngnvk.ybpny> References: <cf9b1ee01002150049o43fced71ucb5776a0a1eaf4cf@mail.gmail.com> <20100215090756.GA54764@icarus.home.lan> <20100215105000.101326yj01j0f64g@webmail.leidinger.net> <20100215122744.GA57382@icarus.home.lan> <20100215161105.14071eiflhc9le68@webmail.leidinger.net> <4B79BA9C.3020402@quip.cz> <alpine.BSF.2.00.1002152024040.74553@pragry.qngnvk.ybpny> <4B7AD0A3.9080701@barryp.org> <alpine.BSF.2.00.1002170321200.14189@pragry.qngnvk.ybpny>
next in thread | previous in thread | raw e-mail | index | archive | help
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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4BB0BC7C.3000801>