41 lines
1001 B
C
41 lines
1001 B
C
#include <linux/compiler.h>
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#include "../tests.h"
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typedef struct _buf {
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char data1;
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char reserved[55];
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char data2;
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} buf __attribute__((aligned(64)));
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static buf buf1 = {
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/* to have this in the data section */
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.reserved[0] = 1,
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};
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static int datasym(int argc __maybe_unused, const char **argv __maybe_unused)
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{
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for (;;) {
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buf1.data1++;
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if (buf1.data1 == 123) {
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/*
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* Add some 'noise' in the loop to work around errata
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* 1694299 on Arm N1.
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*
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* Bias exists in SPE sampling which can cause the load
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* and store instructions to be skipped entirely. This
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* comes and goes randomly depending on the offset the
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* linker places the datasym loop at in the Perf binary.
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* With an extra branch in the middle of the loop that
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* isn't always taken, the instruction stream is no
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* longer a continuous repeating pattern that interacts
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* badly with the bias.
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*/
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buf1.data1++;
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}
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buf1.data2 += buf1.data1;
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}
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return 0;
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}
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DEFINE_WORKLOAD(datasym);
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