On 7/18/19 10:59 AM, Nadav Amit wrote: > I don’t understand how this patch has any impact on this workload. > > I ran it and set a function tracer for any function that is impacted by this > patch: > > # cd /sys/kernel/debug/tracing > # echo text_poke_early > set_ftrace_filter > # echo module_alloc >> set_ftrace_filter > # echo bpf_int_jit_compile >> set_ftrace_filter > # tail -f trace > > Nothing came up. Can you please check if you see any of them invoked on your > setup? Perhaps you have some bpf filters being installed, although even then > this is a one-time (small) overhead for each process invocation.
I think the direct map's structure changed. I noticed the following the 0day data: > 7298e24f904224fa f2c65fb3221adc6b73b0549fc7b > ---------------- --------------------------- > fail:runs %reproduction fail:runs > | | | > :4 50% 2:4 > dmesg.WARNING:at#for_ip_interrupt_entry/0x > %stddev %change %stddev > \ | \ > 10541056 ± 7% +12.1% 11820032 meminfo.DirectMap2> 2.909e+08 > -12.0% 2.56e+08 ± 2% perf-stat.i.iTLB-load-misses > 1876 +10.4% 2071 ± 2% > perf-stat.i.instructions-per-iTLB-miss > 1872 +10.4% 2068 ± 2% > perf-stat.overall.instructions-per-iTLB-miss > 2.899e+08 -12.0% 2.551e+08 ± 2% perf-stat.ps.iTLB-load-misses So something with the direct map changed as did iTLB miss behavior.
