tcg/i386: enable dynamic TLB sizing
As the following experiments show, this series is a net perf gain,
particularly for memory-heavy workloads. Experiments are run on an
Intel(R) Xeon(R) Gold 6142 CPU @ 2.60GHz.
1. System boot + shudown, debian aarch64:
- Before (v3.1.0):
Performance counter stats for './die.sh v3.1.0' (10 runs):
9019.797015 task-clock (msec) # 0.993 CPUs utilized ( +- 0.23% )
29,910,312,379 cycles # 3.316 GHz ( +- 0.14% )
54,699,252,014 instructions # 1.83 insn per cycle ( +- 0.08% )
10,061,951,686 branches # 1115.541 M/sec ( +- 0.08% )
172,966,530 branch-misses # 1.72% of all branches ( +- 0.07% )
9.084039051 seconds time elapsed ( +- 0.23% )
- After:
Performance counter stats for './die.sh tlb-dyn-v5' (10 runs):
8624.084842 task-clock (msec) # 0.993 CPUs utilized ( +- 0.23% )
28,556,123,404 cycles # 3.311 GHz ( +- 0.13% )
51,755,089,512 instructions # 1.81 insn per cycle ( +- 0.05% )
9,526,513,946 branches # 1104.641 M/sec ( +- 0.05% )
166,578,509 branch-misses # 1.75% of all branches ( +- 0.19% )
8.680540350 seconds time elapsed ( +- 0.24% )
That is, a 4.4% perf increase.
2. System boot + shutdown, ubuntu 18.04 x86_64:
- Before (v3.1.0):
56100.574751 task-clock (msec) # 1.016 CPUs utilized ( +- 4.81% )
200,745,466,128 cycles # 3.578 GHz ( +- 5.24% )
431,949,100,608 instructions # 2.15 insn per cycle ( +- 5.65% )
77,502,383,330 branches # 1381.490 M/sec ( +- 6.18% )
844,681,191 branch-misses # 1.09% of all branches ( +- 3.82% )
55.221556378 seconds time elapsed ( +- 5.01% )
- After:
56603.419540 task-clock (msec) # 1.019 CPUs utilized ( +- 10.19% )
202,217,930,479 cycles # 3.573 GHz ( +- 10.69% )
439,336,291,626 instructions # 2.17 insn per cycle ( +- 14.14% )
80,538,357,447 branches # 1422.853 M/sec ( +- 16.09% )
776,321,622 branch-misses # 0.96% of all branches ( +- 3.77% )
55.549661409 seconds time elapsed ( +- 10.44% )
No improvement (within noise range). Note that for this workload,
increasing the time window too much can lead to perf degradation,
since it flushes the TLB *very* frequently.
3. x86_64 SPEC06int:
x86_64-softmmu speedup vs. v3.1.0 for SPEC06int (test set)
Host: Intel(R) Xeon(R) Gold 6142 CPU @ 2.60GHz (Skylake)
5.5 +------------------------------------------------------------------------+
| +-+ |
5 |-+.................+-+...............................tlb-dyn-v5.......+-|
| * * |
4.5 |-+.................*.*................................................+-|
| * * |
4 |-+.................*.*................................................+-|
| * * |
3.5 |-+.................*.*................................................+-|
| * * |
3 |-+......+-+*.......*.*................................................+-|
| * * * * |
2.5 |-+......*..*.......*.*.................................+-+*...........+-|
| * * * * * * |
2 |-+......*..*.......*.*.................................*..*...........+-|
| * * * * * * +-+ |
1.5 |-+......*..*.......*.*.................................*..*.*+-+.*+-+.+-|
| * * *+-+ * * +-+ *+-+ +-+ +-+ * * * * * * |
1 |++++-+*+*++*+*++*++*+*++*+*+++-+*+*+-++*+-++++-++++-+++*++*+*++*+*++*+++|
| * * * * * * * * * * * * * * * * * * * * * * * * * * |
0.5 +------------------------------------------------------------------------+
400.perlb401.bzip403.g429445.g456.hm462.libq464.h471.omn47483.xalancbgeomean
png: https://imgur.com/YRF90f7
That is, a 1.51x average speedup over the baseline, with a max speedup
of 5.17x.
Here's a different look at the SPEC06int results, using KVM as the baseline:
x86_64-softmmu slowdown vs. KVM for SPEC06int (test set)
Host: Intel(R) Xeon(R) Gold 6142 CPU @ 2.60GHz (Skylake)
25 +---------------------------------------------------------------------------+
| +-+ +-+ |
| * * +-+ v3.1.0 |
| * * +-+ tlb-dyn-v5 |
| * * * * +-+ |
20 |-+.................*.*.............................*.+-+......*.*........+-|
| * * * # # * * |
| +-+ * * * # # * * |
| * * * * * # # * * |
15 |-+......*.*........*.*.............................*.#.#......*.+-+......+-|
| * * * * * # # * #|# |
| * * * * +-+ * # # * +-+ |
| * * +-+ * * ++-+ +-+ * # # * # # +-+ |
| * * +-+ * * * ## *| +-+ * # # * # # +-+ |
10 |-+......*.*..*.+-+.*.*........*.##.......++-+.*.+-+*.#.#......*.#.#.*.*..+-|
| * * * +-+ * * * ## +-+ *# # * # #* # # +-+ * # # * * |
| * * * # # * * +-+ * ## * +-+ *# # * # #* # # * * * # # *+-+ |
| * * * # # * * * +-+ * ## * # # *# # * # #* # # * * * # # * ## |
5 |-+......*.+-+*.#.#.*.*..*.#.#.*.##.*.#.#.*#.#.*.#.#*.#.#.*.*..*.#.#.*.##.+-|
| * # #* # # * +-+* # # * ## * # # *# # * # #* # # * * * # # * ## |
| * # #* # # * # #* # # * ## * # # *# # * # #* # # * +-+* # # * ## |
| ++-+ * # #* # # * # #* # # * ## * # # *# # * # #* # # * # #* # # * ## |
|+++*#+#+*+#+#*+#+#+*+#+#*+#+#+*+##+*+#+#+*#+#+*+#+#*+#+#+*+#+#*+#+#+*+##+++|
0 +---------------------------------------------------------------------------+
400.perlbe401.bzi403.gc429445.go456.h462.libqu464.h471.omne4483.xalancbmgeomean
png: https://imgur.com/YzAMNEV
After this series, we bring down the average SPEC06int slowdown vs KVM
from 11.47x to 7.58x.
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <20190116170114.26802-4-cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
54eaf40b8f