igt@perf@polling-small-buf - fail - Failed assertion: abs(n_expect_read_bytes - n_bytes_read) < 0.20 * n_expect_read_bytes

https://intel-gfx-ci.01.org/tree/drm-tip/drmtip_473/fi-tgl-y/igt@perf@polling-small-buf.html

Starting subtest: polling-small-buf
(perf:1047) CRITICAL: Test assertion failure function test_polling_small_buf, file ../tests/perf.c:2348:
(perf:1047) CRITICAL: Failed assertion: abs(n_expect_read_bytes - n_bytes_read) < 0.20 * n_expect_read_bytes
Subtest polling-small-buf failed.
**** DEBUG ****
(perf:1047) INFO: Read 169488 expected 792000 (21.40% of the expected number), polls=214
(perf:1047) CRITICAL: Test assertion failure function test_polling_small_buf, file ../tests/perf.c:2348:
(perf:1047) CRITICAL: Failed assertion: abs(n_expect_read_bytes - n_bytes_read) < 0.20 * n_expect_read_bytes
(perf:1047) igt_core-INFO: Stack trace:
(perf:1047) igt_core-INFO:   #0 ../lib/igt_core.c:1676 __igt_fail_assert()
(perf:1047) igt_core-INFO:   #1 ../tests/perf.c:1094 __real_main4877()
(perf:1047) igt_core-INFO:   #2 ../tests/perf.c:4877 main()
(perf:1047) igt_core-INFO:   #3 ../csu/libc-start.c:344 __libc_start_main()
(perf:1047) igt_core-INFO:   #4 [_start+0x2a]
****  END  ****
Subtest polling-small-buf: FAIL (0.309s)