Hi guys, In light of perf -g stalling (as unwinder was taking ~3million cycles for non existent entries), I've revamped the dwarf unwinder.
There are some optim tweaks and much of it is "De-generalization" for things which we can safely assume on ARC. Crude Instrumentation shows following improvements per unwinder call: - Avg time come down from ~4650 cycles to ~2794 cycles (+40%) - Max time come down 9793 cycles to 5987 cycles This is on a SMP FPGA config @ 75 MHz It seems much of time (65%) is taken for binary lookup thru ~12k FDE entries, roughly 13 lookups, each likely a dcache miss. git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc # topic-unwinder-rework-4-instrument -Vineet Vineet Gupta (17): ARC: dw2 unwind: Elide generation of const propagated clones ARC: dw2 unwind: remove unused cruft ARC: dw2 unwind: Remove handling of for signal frame ARC: dw2 unwind: Remove FP based unwinding ARC: dw2 unwind: Better printing ARC: dw2 unwind: Don't verify Main FDE Table size everytime ARC: dw2 unwind: Refactor the FDE lookup table (eh_frame_header) code ARC: dw2 unwind: Don't verify FDE lookup table metadata ARC: dw2 unwind: Use striaght forward code to implement binary lookup ARC: dw2 unwind: CIE parsing/validation done only once at startup ARC: dw2 unwind: Elide REG_INVALID check ARC: dw2 unwind: Elide a loop if DW_CFA_register not present ARC: dw2 unwind: Assume all regs to be unsigned long ARC: dw2 unwind: No need for __get_user ARC: dw2 unwind: Single exit point for instrumentation ARC: dw2 unwind: skip regs not updated xxx: instrument arch/arc/include/asm/unwind.h | 47 +-- arch/arc/kernel/Makefile | 1 + arch/arc/kernel/unwind.c | 806 ++++++++++++++++-------------------------- 3 files changed, 313 insertions(+), 541 deletions(-) -- 1.9.1 _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
