diff options
| author | Emilio G. Cota | 2017-04-27 05:29:24 +0200 |
|---|---|---|
| committer | Richard Henderson | 2017-06-05 18:25:42 +0200 |
| commit | 6f1653180f5701c6a8f1b35b89a80b1e3260928e (patch) | |
| tree | 2fca38d3e3019e3df4885ebe34bfae8e25a69e18 /include/exec/tb-hash.h | |
| parent | target/i386: optimize indirect branches (diff) | |
| download | qemu-6f1653180f5701c6a8f1b35b89a80b1e3260928e.tar.gz qemu-6f1653180f5701c6a8f1b35b89a80b1e3260928e.tar.xz qemu-6f1653180f5701c6a8f1b35b89a80b1e3260928e.zip | |
tb-hash: improve tb_jmp_cache hash function in user mode
Optimizations to cross-page chaining and indirect branches make
performance more sensitive to the hit rate of tb_jmp_cache.
The constraint of reserving some bits for the page number
lowers the achievable quality of the hashing function.
However, user-mode does not have this requirement. Thus,
with this change we use for user-mode a hashing function that
is both faster and of better quality than the previous one.
Measurements:
Note: baseline (i.e. speedup == 1x) is QEMU v2.9.0.
- SPECint06 (test set), x86_64-linux-user. Host: Intel i7-6700K @ 4.00GHz
2.2x +-+--------------------------------------------------------------------------------------------------------------+-+
| |
| jr |
2x +jr+multhash +....................................................+++++...................................+-+
| jr+hash |$$$ |
| |$+$ |
| ### $ |
1.8x +-+......................................................................#|#.$...................................+-+
| ++#+# $ |
| |# # $ |
1.6x +-+....................................................................***.#.$....................++$$$..........+-+
| $$$ *+* # $ |$+$ |
| ++$$$ ### $ * * # $ +++|$ $ |
| ++###+$ # # $ * * # $ ### ****## $ |
1.4x +-+...................***+#.$.........***.#.$..........................*.*.#.$...........#+#$$.*++*|#.$..........+-+
| *+* # $ * * # $ * * # $ # # $ * *+# $ |
| * * # $ +++++ * * # $ * * # $ *** # $ * * # $ ###$$ |
1.2x +-+...................*.*.#.$.***##$$.*.*.#.$..........................*.*.#.$.........*.*.#.$.*..*.#.$.***+#+$..+-+
| * * # $ *+* # $ * * # $ +++ * * # $ ++###$$ * * # $ * * # $ * * # $ |
| ***##$$ * * # $ * * # $ * * # $ ***##$$ ++### * * # $ *** #+$ * * # $ * * # $ * * # $ |
| *+*+#+$ ***##$$$ * * # $ * * # $ * * # $ *+* # $ ++####$$ ***+# * * # $ * * # $ * * # $ * * # $ * * # $ |
1x +-++-*+*+#+$+*+*+#-+$+*+*-#+$+*+*+#+$+*+*+#+$+*-*+#+$+***++#+$+*+*+#$$+*+*+#+$+*+*+#+$+*+*-#+$+*+-*+#+$+*+*+#+$-++-+
| * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ |
| * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ * * # $ |
0.8x +-+--***##$$-***##$$$-***##$$-***##$$-***##$$-***##$$-***###$$-***##$$-***##$$-***##$$-***##$$-****##$$-***##$$--+-+
astar bzip2 gcc gobmk h264ref hmmlibquantum mcf omnetpperlbench sjengxalancbmk hmean
png: http://imgur.com/4UXTrEc
Here I also tried the hash function suggested by Paolo ("multhash"):
return ((uint64_t) (pc * 2654435761) >> 32) & (TB_JMP_CACHE_SIZE - 1);
As you can see it is just as good as the other new function ("hash"),
which is what I ended up going with.
- SPECint06 (train set), x86_64-linux-user. Host: Intel i7-6700K @ 4.00GHz
2.6x +-+--------------------------------------------------------------------------------------------------------------+-+
| |
| jr ### |
2.4x +jr+hash...........................................................................................#.#...........+-+
| # # |
| # # |
2.2x +-+................................................................................................#.#...........+-+
| # # |
| # # |
2x +-+................................................................................................#.#...........+-+
| **** # |
| * * # |
1.8x +-+.............................................................................................*..*.#...........+-+
| +++ * * # |
| #### #### * * # |
1.6x +-+......................................####.............................#..#.****..#..........*..*.#...........+-+
| +++ #++# **** # * * # #### * * # |
| ### # # * * # * * # # # * * # |
1.4x +-+...................****+#..........****..#..........................*..*..#.*..*..#....#..#..*..*.#...........+-+
| *++* # * * # * * # * * # *** # * * # #### |
| * * # #### * * # * * # * * # * * # * * # **** # |
1.2x +-+...................*..*.#..****++#.*..*..#..........................*..*..#.*..*..#..*.*..#..*..*.#..*..*..#..+-+
| ****### * * # * * # * * # * * # * * # * * # * * # * * # |
| * * # ***### * * # * * # * * # ****## * * # * * # * * # * * # * * # |
1x +-+--****###--***###--****##--****###-****###--***###--***###--****##--****###-****###--***###--****##--****###--+-+
astar bzip2 gcc gobmk h264ref hmmlibquantum mcf omnetpperlbench sjengxalancbmk hmean
png: http://imgur.com/ArCbHqo
- NBench, x86_64-linux-user. Host: Intel i7-6700K @ 4.00GHz
1.12x +-+-------------------------------------------------------------------------------------------------------------+-+
| |
| jr +++ |
1.1x +jr+hash...........................................................####.........................................+-+
| +++#| # |
| | #++# |
1.08x +-+................................+++................+++.+++..*****..#.........................................+-+
| | +++ | | * | * # |
| | | | | *+++* # |
1.06x +-+................................****###.............|...|...*...*..#.........................+++.............+-+
| *| * |# ****### * * # | |
| *| *++# *| * |# * * # #### |
1.04x +-+................................*++*..#............*|.*.|#..*...*..#........................#.|#.............+-+
| * * # *++*++# * * # +++#++# |
| * * # * * # * * # | # # +++#### |
1.02x +-+................................*..*..#......+++...*..*..#..*...*..#.....................****..#..*****++#...+-+
| +++ * * # +++ | * * # * * # +++ *| * # *+++* # |
| +++ | +++ +++ ++++++ * * # *****### * * # * * # | +++ ++++++ *++* # * * # |
1x +-++-+++++####++****###++++-+####+-*++*++#-+*+++*-+#++*++*++#++*+-+*++#+-+++####-+*****###++*++*++#++*+-+*++#+-++-+
| *****| # *++* |# *****| # * * # * *++# * * # * * # **** |# * * # * * # * * # |
| * | *| # * *++# * | *++# * * # * * # * * # * * # *| *++# * * # * * # * * # |
0.98x +-+...*.|.*++#..*..*..#..*+++*..#..*..*..#..*...*..#..*..*..#..*...*..#..*++*..#..*...*..#..*..*..#..*...*..#...+-+
| *+++* # * * # * * # * * # * * # * * # * * # * * # * * # * * # * * # |
| * * # * * # * * # * * # * * # * * # * * # * * # * * # * * # * * # |
0.96x +-+---*****###--****###--*****###--****###--*****###--****###--*****###--****###--*****###--****###--*****###---+-+
ASSIGNMENT BITFIELD FOURFP EMULATION HUFFMAN LU DECOMPOSITIONEURAL NNUMERIC SOSTRING SORT hmean
png: http://imgur.com/ZXFX0hJ
- NBench, arm-linux-user. Host: Intel i7-4790K @ 4.00GHz
1.3x +-+-------------------------------------------------------------------------------------------------------------+-+
| #### |
| jr # # +++ |
1.25x +jr+hash.....................#..#...........................................####................................+-+
| # # # # |
| # # # # |
1.2x +-+..........................#..#...........................................#..#................................+-+
| # # # # |
| # # # # |
1.15x +-+..........................#..#...........................................#..#................................+-+
| # # #### # # |
| # # # # # # |
1.1x +-+..........................#..#..................................#..#.....#..#................................+-+
| # # # # # # +++ |
| # # #### # # # # #### |
1.05x +-+..........................#..#...............#..#.....####......#..#.....#..#.........................#..#...+-+
| # # # # # # # # # # +++ # # |
| +++ ***** # #### ***** # # # +++# # **** # ****### # # |
1x +-++-+*****###++****+++++*+-+*++#+-****++#-+*+++*-+#+++++#++#++*****++#+-*++*++#-+*****-++++*++*++#++*****++#+-++-+
| * * # * * | * * # * * # * * # **** # * * # * * # * *### * *++# * * # |
| * * # * *### * * # * * # * * # * * # * * # * * # * * # * * # * * # |
0.95x +-+...*...*..#..*..*.|#..*...*..#..*..*..#..*...*..#..*..*..#..*...*..#..*..*..#..*...*..#..*..*..#..*...*..#...+-+
| * * # * * |# * * # * * # * * # * * # * * # * * # * * # * * # * * # |
| * * # * * |# * * # * * # * * # * * # * * # * * # * * # * * # * * # |
0.9x +-+---*****###--****###--*****###--****###--*****###--****###--*****###--****###--*****###--****###--*****###---+-+
ASSIGNMENT BITFIELD FOURFP EMULATION HUFFMAN LU DECOMPOSITIONEURAL NNUMERIC SOSTRING SORT hmean
png: http://imgur.com/FfD27ey
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1493263764-18657-12-git-send-email-cota@braap.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Diffstat (limited to 'include/exec/tb-hash.h')
| -rw-r--r-- | include/exec/tb-hash.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/exec/tb-hash.h b/include/exec/tb-hash.h index 2c27490cb8..b1fe2d0161 100644 --- a/include/exec/tb-hash.h +++ b/include/exec/tb-hash.h @@ -22,6 +22,8 @@ #include "exec/tb-hash-xx.h" +#ifdef CONFIG_SOFTMMU + /* Only the bottom TB_JMP_PAGE_BITS of the jump cache hash bits vary for addresses on the same page. The top bits are the same. This allows TLB invalidation to quickly clear a subset of the hash table. */ @@ -45,6 +47,16 @@ static inline unsigned int tb_jmp_cache_hash_func(target_ulong pc) | (tmp & TB_JMP_ADDR_MASK)); } +#else + +/* In user-mode we can get better hashing because we do not have a TLB */ +static inline unsigned int tb_jmp_cache_hash_func(target_ulong pc) +{ + return (pc ^ (pc >> TB_JMP_CACHE_BITS)) & (TB_JMP_CACHE_SIZE - 1); +} + +#endif /* CONFIG_SOFTMMU */ + static inline uint32_t tb_hash_func(tb_page_addr_t phys_pc, target_ulong pc, uint32_t flags) { |