On Wed, Aug 15, 2012 at 12:20 PM, Ezequiel Garcia <[email protected]> wrote: > Hi Steven, > > This patch is my first attempt to address the "early tracing issue". > Right now, trace events are registered on fs_initcall, which is very late > if you want to capture boot-up events. > > This feature is in developers wish list as this old (2009) thread shows [1]. > > By splitting the initialization, separating the ftrace enable from the > sysfs entry > creation, it is possible to move events enable to early_initcall. > (which is also late, but I wouldn't expect more from such a small patch). > > Without this patch, and using > "trace_event=kmem:kmalloc,kmem:kmalloc_node,kmem:kfree" > as kernel parameter, on a bare kernel I can start capturing kmallocs > from ~0.4 secs, > and I get 186 callers. > > This patch moves the capture to ~ 0.2 secs and captures 220 callers. > > The caller count is inaccurate since gcc does some automatic inlining > (I have another RFC PATCH for that), but it shows a rough increase. > > Also, this enable is not time-consuming: > [ 0.190000] calling event_trace_enable+0x0/0xad @ 1 > [ 0.190000] initcall event_trace_enable+0x0/0xad returned 0 after 0 usecs > > This patch is intended to trigger this discussion: to be honest I'm > not sure how ugly > this is. So some feedback about it would be greatly appreciated. > > Also, I'd like to ask for some guidelines (not solutions, just some > guidelines) > on how to attack this problem. > I'm interesting on capturing kmem events, from the very first kmalloc onwards. > Though, it would be nice to extend the solution to other event classes. > > Thanks, > Ezequiel. > > [1] http://lkml.indiana.edu/hypermail/linux/kernel/0911.3/00036.html
I forgot to add this work is part of a project funded by CE workgroup. You can find more details here: http://elinux.org/Kernel_dynamic_memory_allocation_tracking_and_reduction Thanks, Ezequiel. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
