The xen trace facility is not enabled by default. I''m working on some tools that use it, and I''m concerned that the tool will not work for customers who buy packaged distro''s. What are the arguments for keeping trace disabled? Is it just the memory consumed by the trace buffers? It doesn''t appear to me that there would be any impact beyond that. What is the possibility of making tracing enabled by default? Rob _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On 6 Sep 2005, at 23:51, Rob Gardner wrote:> The xen trace facility is not enabled by default. I''m working on some > tools that use it, and I''m concerned that the tool will not work for > customers who buy packaged distro''s. What are the arguments for > keeping trace disabled? Is it just the memory consumed by the trace > buffers? It doesn''t appear to me that there would be any impact beyond > that. What is the possibility of making tracing enabled by default?It''s up to the distros to decide what options they anable in their default Xen package imo. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser wrote:> > On 6 Sep 2005, at 23:51, Rob Gardner wrote: > >> The xen trace facility is not enabled by default. I''m working on some >> tools that use it, and I''m concerned that the tool will not work for >> customers who buy packaged distro''s. What are the arguments for >> keeping trace disabled? Is it just the memory consumed by the trace >> buffers? It doesn''t appear to me that there would be any impact >> beyond that. What is the possibility of making tracing enabled by >> default? > > > It''s up to the distros to decide what options they anable in their > default Xen package imo.Yes, but they are likely to stick with the xen defaults unless they have a reason for changing them. In the case of tracing, their reaction is likely to be that "tracing" sounds like some debugging feature, will probably be bad for performance, so let''s leave it turned off. So could you state what performance impact you think tracing will actually have on the system? Thanks, Rob _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> Yes, but they are likely to stick with the xen defaults unless they have > a reason for changing them. In the case of tracing, their reaction is > likely to be that "tracing" sounds like some debugging feature, will > probably be bad for performance, so let''s leave it turned off. So could > you state what performance impact you think tracing will actually have > on the system?Trace buffers can be disabled on the commandline to avoid the memory overhead and the cost of calling the "trace" function itself via the TRACE_xD macros should not be measurable. Cheers, Mark _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
For arguments'' sake I''m attaching a (build tested, hg import-able) changeset I knocked up to unconditionally enable the trace buffer. The default size is 10 pages / online CPU (runtime configurable). Cheers, Mark> > Yes, but they are likely to stick with the xen defaults unless they have > > a reason for changing them. In the case of tracing, their reaction is > > likely to be that "tracing" sounds like some debugging feature, will > > probably be bad for performance, so let''s leave it turned off. So could > > you state what performance impact you think tracing will actually have > > on the system? > > Trace buffers can be disabled on the commandline to avoid the memory > overhead and the cost of calling the "trace" function itself via the > TRACE_xD macros should not be measurable. > > Cheers, > Mark > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel