Posts

From time to time students ask me for book recommendations. Subsequently my personal top five(+/-) lists for each category (a little bit Linux (kernel) and C biased). I believe these are the books you should read when you are interested in one particular topic: Computer Architecture Processor Microarchitecture: An Implementation Perspective; Antonio Gonzalez and Fernando Latorre and Grigorios Magklis; The title says it all! A book you should probably read after you read all other books in this section....

Introduction First off all: this guide is no replacement for the great OpenWrt documentation. Rather this guide show what software I use and how I configure the system. Sure, some software components smells fishy, the hardware could be better and so on. But this setup is great and fullfills my requirements and at least do not use any proprietary components like FritzBox (who want’s closed source in the private network? Do they backport all kernel bugfixes?...

Memory latency and bandwidth is one major performance factor. I once visualized all memory subsystems and their latency impact of my Xeon 5500 in a illustration.

I track some Linux kernel development subsystems: Linus, perf, network (davem’s) net-next and lkvm. Additionally I add two historic Linux repositories: Thomas post 2.4 tree and davej’s pre 2.4 branch. In the earlier git days I referenced cloned locally. Later I started to add remotes within one repository. To setup this environment the following commands may be helpful: # create a vanilla git container mkdir linux; cd linux git init # add remotes git remote add --track torvalds git://git....

Today some ideas how Captcp generated throughput graphs can be modified and improved. We start with a pcap file (captured via tcpdump or wireshark). We create a output directory, called graphs and finally start captcp and visualize one TCP flow. The number of the connection and flow (-f 45.2) is a result of captcp’s statistic module - I just picked up one random flow within the capture file. The output of captcp is saved in the directory graphs....

Today I want to demonstrate how captcp outperform wireshark for TCP flow analysis. This posting focus on throughput analysis for a specific TCP flow. In a separate posting I will demonstrate how Gnuplot can be tweaked to generate a nice image ready for web publishing or for your bachelor/master/phd thesis. The need for this posting arise from discussions with captcp users where I think that the workflow with captcp and Gnuplot is not ideal....

back in the days, with black monitors, leather jackets, red phones, 5 1⁄4" floppy disks, … - I like via Amazon

Just for the statistical guys reading my blog: Jiri Olsa posted a patch today to extend perf diff to show differential profiling. Perf diff now support three diff computations: delta: the current default one ratio: ratio differential profile wdiff: weighted differential profile The idea goes back to Paul E. McKenney and his paper Differential Profiling. Nice reading!

For a new MANET protocol I started to verify the security concept. Not from a security point of view, rather from a protocol feasibility point of view. The security concept is based on existing security protocols. I just removed dynamic components like key exchange and the like (to be correct: dynamic aspects are done by special messages and not that tight linked with the protocol). The result should be a very lean TLV, containing only required security data without padding issues are “reserved” bits....

John Nagle (no, not the TCP Nagle ;-) proposed a extension to C to keep array information over the call context to do bounds checks. His proposal Safe Arrays and Pointers for C through compatible additions to the language is a nice reading. On the GCC maillinglist the responses are mixed: more questions and doubts if such a extension will and can be adopted by the users.