Re: get the mapping of <key, syscallname>

["Jose R. Santos" <jrs at us dot ibm dot com>]

Frank Ch. Eigler wrote:

> Li Guanglei <guanglei@cn.ibm.com> writes:
>
> > One of my tapsets will log the syscall name got from
> > CONTEXT->probe_point. [...]
>
> Why not use the "name" variable set by the syscalls tapset?
>  
LKET does not currently use the syscall tapset because it doesnt use the 
extra information that this tapset collects from each systemcall.  In 
order to improve performance, we keep the system call trace as simple as 
possible.

> > [...] I want to log the key of syscall name, and later the
> > post-processing app in user space will figure out the syscall name
> > represented by corresponding keys. [...]
>
> As does Martin, I wonder if this is a good place to spend your
> optimization energies.  Anyway, one possibility is to have the
> syscalls tapset also define a system call number variable.
>  

Its not just the string printing that's costly, its also searching the 
system call name with in CONTEXT->probe_point.  Avoiding searching and 
printing of the syscall string can provide between 3-6% performance 
improvements on SPECjbb results.

> - FChE
>