#include <linux/compiler.h> #include "../tests.h" typedef struct _buf { char data1; char reserved[55]; char data2; } buf __attribute__((aligned(64))); static buf buf1 = { /* to have this in the data section */ .reserved[0] = 1, }; static int datasym(int argc __maybe_unused, const char **argv __maybe_unused) { for (;;) { buf1.data1++; if (buf1.data1 == 123) { /* * Add some 'noise' in the loop to work around errata * 1694299 on Arm N1. * * Bias exists in SPE sampling which can cause the load * and store instructions to be skipped entirely. This * comes and goes randomly depending on the offset the * linker places the datasym loop at in the Perf binary. * With an extra branch in the middle of the loop that * isn't always taken, the instruction stream is no * longer a continuous repeating pattern that interacts * badly with the bias. */ buf1.data1++; } buf1.data2 += buf1.data1; } return 0; } DEFINE_WORKLOAD(datasym);