On Tue, Sep 13, 2016 at 06:45:00PM +0900, Byungchul Park wrote: > Currently, x86 implementation of save_stack_trace() is walking all stack > region word by word regardless of what the trace->max_entries is. > However, it's unnecessary to walk after already fulfilling caller's > requirement, say, if trace->nr_entries >= trace->max_entries is true. > > I measured its overhead and printed its difference of sched_clock() with > my QEMU x86 machine. The latency was improved over 70% when > trace->max_entries = 5. This code will (probably) be obsoleted soon with my new unwinder. Also, my previous comment was ignored: Instead of adding a new callback, why not just check the ops->address() return value? It already returns an error if the array is full. I think that would be cleaner and would help prevent more callback sprawl. -- Josh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>