Date: Thu, 25 Nov 2010 13:04:49 -0800 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: Adam Vande More <amvandemore@gmail.com> Cc: freebsd-stable@freebsd.org, Andriy Gapon <avg@freebsd.org> Subject: Re: top io mode Message-ID: <20101125210449.GA57788@icarus.home.lan> In-Reply-To: <20101125205733.GA56845@icarus.home.lan> References: <AANLkTikrKevf3x4nyi6=8Yz0BW=yZzf0W_Xa3XGQXy8N@mail.gmail.com> <4CEE88D9.4070200@DataIX.net> <AANLkTincWrdhq3my_RARtB17mneT77YZubQbFCN1Swzp@mail.gmail.com> <20101125200813.GA56066@icarus.home.lan> <AANLkTinVq8f6miLjqePEBOjN3CfhZJcPf%2B8njiKwTaL3@mail.gmail.com> <20101125205733.GA56845@icarus.home.lan>
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On Thu, Nov 25, 2010 at 12:57:33PM -0800, Jeremy Chadwick wrote: > On Thu, Nov 25, 2010 at 02:28:35PM -0600, Adam Vande More wrote: > > On Thu, Nov 25, 2010 at 2:08 PM, Jeremy Chadwick > > <freebsd@jdc.parodius.com>wrote: > > > > > > Well the top bug didn't seem to resolve my actual issue and yes it it a > > > > complete ZFS system. Problem is that the HD activity indicator light is > > > > constantly flickering even though should be minimal activity. top still > > > > shows no activity around the blinks, and there's no swapping happening > > > > although gstat does seem to roughly match the blinks. I can't tell what > > > > your patch does, would it enable me to see what's touching the disk? > > > > > > Please try using gstat(8) instead. > > > > > > > Like I said gstat shows activity, but I have no way find what process is > > causing the activity unless there is some hidden gstat option I'm unaware > > of. > > Sorry, I missed that part of your explanation, my apologies. > > > to be more clear, if I have top -m io in one terminal, I see no movement in > > the READ/WRITE columns. > > > > while polling gstat output I captured an IO "spike" > > > > http://pastebin.com/f84nuzxt > > > > the percent busy is at 0.00 for every entry with the exception of these > > spikes. > > I don't have an answer for you, other than "maybe top shows a different > 'kind' of I/O than what gstat or iostat does". > > Only ideas I have: > > 1) Possibly acct(2) with sa(8) could provide some insight, but I have no > idea how well it works. > > 2) I see some ps(8) -O parameters labelled "inblk" and "oublk", but I'm > not sure what "block" means given the man page context. If these are > "disk blocks", then possibly a shell script that repetitively calls ps > with these arguments could narrow it down. > > It's too bad, since sar(1M) on Solaris can be used to achieve exactly > what you're looking for -- and the closest thing to that on FreeBSD that > I know of is acct(2) and sa(8). Bad form to follow up to my own Email of course, but some discussion material: "top -m io" doesn't show any I/O writes, while gstat(8) does, and to numerous devices all which make up some form of ZFS pool. If you do something like "dd if=/dev/urandom of=/pool/file bs=64k", does "top -m io" show write I/O for the "dd" process? If so, then possibly ZFS "internally" is doing something quietly/behind the scenes (such as a disk flush or some sort of internal transaction "thing"), thus the kernel would be responsible and not a process. So that said, how about "top -S -m io -U root" instead, which includes system processes, since we can (probably) assume a non-root process isn't responsible? HTH. -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |
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