On Tue, Feb 15, 2011 at 4:26 PM, Frank Ch. Eigler <[email protected]> wrote: > > Julien Desfossez <[email protected]> writes: > >> LTTng-UST vs SystemTap userspace tracing benchmarks > > Thank you. > >> [...] For flight recorder tracing, UST is 289 times faster than >> SystemTap on an 8-core system with a LTTng kernel and 279 times with >> a vanilla+utrace kernel. > > This is not that surprising, considering how the two tools work. UST > does its work in userspace, and is therefore focused on an individual > process's activities. Systemtap does its work in kernelspace, and can > therefore focus on many different processes and the kernel at the same > time. This entails some ring transitions. > > (One may imagine a future version of systemtap where scripts that > happen to independently probe single processes are executed with a > pure userspace backend, but this is not in our immediate roadmap.)
What is the fundamental mechanism that UST and SystemTap use for tracing? e.g. Here's a guess: UST: a conditional function call within the same process SystemTap: a software interrupt on x86 I don't know the implementations details but would be interested in understanding this. Stefan _______________________________________________ ltt-dev mailing list [email protected] http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
