Tuning the OpenZFS write throttle

In previous posts I discussed the problems with the legacy ZFS write throttle that cause degraded performance and wildly variable latencies. I then presented the new OpenZFS write throttle and I/O scheduler that Matt Ahrens and I designed. In addition to solving several problems in ZFS, the new approach was designed to be easy to [...]





Posted on August 31, 2014 at 4:16 pm by ahl · Permalink · 3 Comments
In: ZFS · Tagged with: , , , , ,

illumos hackathon 2012: user-land types for DTrace

At the illumos hackathon last week, Robert Mustacchi and I prototyped better support for manipulating user-land structures. As anyone who’s used it knows, DTrace is currently very kernel-centric — this both reflects the reality of how operating systems and DTrace are constructed, and the origins of DTrace itself in the Solaris Kernel Group. Discussions at [...]





Posted on October 11, 2012 at 4:28 pm by ahl · Permalink · 3 Comments
In: DTrace · Tagged with: , , , ,

BTrace: DTrace for Java… ish

DTrace first peered into Java in early 2005 thanks to an early prototype by Jarod Jenson that led eventually to the inclusion of USDT probes in the HotSpot JVM. If you want to see where, say, the java.net.SocketOutputStream.write() method is called, you can simply run this DTrace script: hotspot$target:::method-entry /copyinstr(arg1, arg2) == “java/net/SocketOutputStream” && copyinstr(arg3, [...]





Posted on April 24, 2012 at 7:29 am by ahl · Permalink · 4 Comments
In: DTrace · Tagged with: , ,

dtrace.conf(12) wrap-up

For the second time in as many quadrennial dtrace.confs, I was impressed at how well the unconference format worked out. Sharing coffee with the DTrace community, it was great to see some of the oldest friends of DTrace — Jarod Jenson, Stephen O’Grady, Jonathan Adams to name a few — and to put faces to [...]





Posted on April 9, 2012 at 6:03 pm by ahl · Permalink · 5 Comments
In: DTrace · Tagged with: , , , , , , , ,

DTrace OEL update

A few months ago I took DTrace on OEL for a spin after Oracle announced it. The results were ugly; as one of the authors of DTrace, I admit to being shocked by shoddiness of the effort. Yesterday, Oracle dropped an updated beta so I wanted to see how far they’ve come in the 4+ months [...]





Posted on February 23, 2012 at 10:00 pm by ahl · Permalink · 8 Comments
In: DTrace · Tagged with: , ,

The case of the un-unmountable tmpfs

Every once in a rare while our development machines encounter an fatal error during boot because we couldn’t unmount tmpfs. This weekend I cracked the case, so I thought I’d share my uses of boot-time DTrace, and the musty corners of the operating systems that I encountered along the way. First I should explain a [...]





Posted on December 12, 2011 at 4:39 pm by ahl · Permalink · One Comment
In: DTrace · Tagged with: , , , , ,

Welcome Matt Amdur

It’s my pleasure to welcome Matt Amdur to Delphix, to the world of DTrace, and — just today — to the blogosphere. Matt joined Delphix about two months after 10 years of software engineering, most recently at VMware. Matt and I met in at Brown University in 1997 where we worked together closely for all [...]





Posted on October 12, 2011 at 10:40 pm by ahl · Permalink · Comments Closed
In: Delphix · Tagged with: , ,

Oracle’s port: this is not DTrace

After writing about Oracle’s port of DTrace to OEL, I wanted to take it for a spin. Following the directions that Wim Coekaerts spelled out, I installed and configured a VM to run OEL with Oracle’s nascent DTrace port. Setting up the system was relatively painless. Here’s my first DTrace invocation on OEL: [root@screven ~]# [...]





Posted on October 10, 2011 at 10:43 pm by ahl · Permalink · 13 Comments
In: DTrace · Tagged with: , ,

DTrace for Linux

Yesterday (October 4, 2011) Oracle made the surprising announcement that they would be porting some key Solaris features, DTrace and Zones, to Oracle Enterprise Linux. As one of the original authors, the news about DTrace was particularly interesting to me, so I started digging. I should note that this isn’t the first time I’ve written [...]





Posted on October 5, 2011 at 9:51 pm by ahl · Permalink · 32 Comments
In: DTrace · Tagged with: , , , , , , ,

Delphix launch at DEMO

At 4:08pm today, we will launch Delphix Server at DEMO. At the presentation, Richard Rothschild from TiVo will describe how they have been using Delphix. TiVo, of course, has been canonized as technology that changes the way we live or work. My past work on DTrace was described by users as “TiVo for the kernel” [...]





Posted on September 14, 2010 at 9:35 pm by ahl · Permalink · Comments Closed
In: Delphix · Tagged with: , , , , ,