Date: Fri, 19 Feb 2016 13:51:21 -0500 From: Tom Curry <thomasrcurry@gmail.com> To: "Michael W. Lucas" <mwlucas@michaelwlucas.com> Cc: fs@freebsd.org Subject: Re: dtracing ZFS on FreeBSD Message-ID: <CAGtEZUB31Uwk1Ge_DPB_scP6Sw6D4s-w6WgbXr_k_zDL0DB7dQ@mail.gmail.com> In-Reply-To: <20160219180716.GA46881@mail.michaelwlucas.com> References: <20160219180716.GA46881@mail.michaelwlucas.com>
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On Fri, Feb 19, 2016 at 1:07 PM, Michael W. Lucas <mwlucas@michaelwlucas.co= m > wrote: > Hi, > > I'm trying get Adam Leventhal's dtrace script for measuring latency > and number of operations on a pool > (http://dtrace.org/blogs/ahl/2014/08/31/openzfs-tuning/). Asking for > guidance here because it's a filesystem thing and the dtrace list is > dead. > > The script is: > > #pragma D option aggpack > #pragma D option quiet > > fbt::vdev_queue_max_async_writes:entry > { > self->spa =3D args[0]; > } > fbt::vdev_queue_max_async_writes:return > /self->spa && self->spa->spa_name =3D=3D $$1/ > { > @ =3D lquantize(args[1], 0, 30, 1); > } > > tick-1s > { > printa(@); > clear(@); > } > > fbt::vdev_queue_max_async_writes:return > /self->spa/ > { > self->spa =3D 0; > } > > When I run it: > > # dtrace -s q.d zroot > > most lines look like this: > > min .--------------------------------. max | count > < 0 : : >=3D 30 | 0 > dtrace: 15857 dynamic variable drops with non-empty dirty list > > My reading of dtrace discussions says I'm losing data here. I suspect > this is the data I'm actually interested in. > > Sometimes, the scale gets a marker on it. Pardon the weird characters: > > min .--------------------------------. max | count > < 0 : =E2=96=88 : >=3D 30 | 3438 > > > Or there's > > min .--------------------------------. max | count > < 0 : =E2=96=81=E2=96=82=E2=96=83=E2=96=85 = : >=3D 30 | 19172 > > Any thoughts on why? > > Thanks, > =3D=3Dml > > -- > Michael W. Lucas - mwlucas@michaelwlucas.com, Twitter @mwlauthor > http://www.MichaelWLucas.com/, http://blather.MichaelWLucas.com/ > > > For the variable drops you could try increasing the buffer size, I know I ran into this when I was tracing something very noisy and it definitely helped. #pragma D option bufsize=3D1m http://dtrace.org/guide/chp-buf.html
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