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We don't have an idle zstreams list anymore and our write path now works
absolutely differently, preventing preemption during compression. This
removes possibilities of read paths preempting writes at wrong places
(which could badly affect the performance of both paths) and at the same
time opens the door for a move from custom LZO/LZ4 compression backends
implementation to a more generic one, using crypto compress API.
Joonsoo Kim [1] attempted to do this a while ago, but faced with the
need of introducing a new crypto API interface. The root cause was the
fact that crypto API compression algorithms require a compression stream
structure (in zram terminology) for both compression and decompression
ops, while in reality only several of compression algorithms really need
it. This resulted in a concept of context-less crypto API compression
backends [2]. Both write and read paths, though, would have been
executed with the preemption enabled, which in the worst case could have
resulted in a decreased worst-case performance, e.g. consider the
following case:
CPU0
zram_write()
spin_lock()
take the last idle stream
spin_unlock()
<< preempted >>
zram_read()
spin_lock()
no idle streams
spin_unlock()
schedule()
resuming zram_write compression()
but it took me some time to realize that, and it took even longer to
evolve zram and to make it ready for crypto API. The key turned out to be
-- drop the idle streams list entirely. Without the idle streams list we
are free to use compression algorithms that require compression stream for
decompression (read), because streams are now placed in per-cpu data and
each write path has to disable preemption for compression op, almost
completely eliminating the aforementioned case (technically, we still have
a small chance, because write path has a fast and a slow paths and the
slow path is executed with the preemption enabled; but the frequency of
failed fast path is too low).
TEST
====
- 4 CPUs, x86_64 system
- 3G zram, lzo
- fio tests: read, randread, write, randwrite, rw, randrw
test script [3] command:
ZRAM_SIZE=3G LOG_SUFFIX=XXXX FIO_LOOPS=5 ./zram-fio-test.sh
BASE PATCHED
jobs1
READ: 2527.2MB/s 2482.7MB/s
READ: 2102.7MB/s 2045.0MB/s
WRITE: 1284.3MB/s 1324.3MB/s
WRITE: 1080.7MB/s 1101.9MB/s
READ: 430125KB/s 437498KB/s
WRITE: 430538KB/s 437919KB/s
READ: 399593KB/s 403987KB/s
WRITE: 399910KB/s 404308KB/s
jobs2
READ: 8133.5MB/s 7854.8MB/s
READ: 7086.6MB/s 6912.8MB/s
WRITE: 3177.2MB/s 3298.3MB/s
WRITE: 2810.2MB/s 2871.4MB/s
READ: 1017.6MB/s 1023.4MB/s
WRITE: 1018.2MB/s 1023.1MB/s
READ: 977836KB/s 984205KB/s
WRITE: 979435KB/s 985814KB/s
jobs3
READ: 13557MB/s 13391MB/s
READ: 11876MB/s 11752MB/s
WRITE: 4641.5MB/s 4682.1MB/s
WRITE: 4164.9MB/s 4179.3MB/s
READ: 1453.8MB/s 1455.1MB/s
WRITE: 1455.1MB/s 1458.2MB/s
READ: 1387.7MB/s 1395.7MB/s
WRITE: 1386.1MB/s 1394.9MB/s
jobs4
READ: 20271MB/s 20078MB/s
READ: 18033MB/s 17928MB/s
WRITE: 6176.8MB/s 6180.5MB/s
WRITE: 5686.3MB/s 5705.3MB/s
READ: 2009.4MB/s 2006.7MB/s
WRITE: 2007.5MB/s 2004.9MB/s
READ: 1929.7MB/s 1935.6MB/s
WRITE: 1926.8MB/s 1932.6MB/s
jobs5
READ: 18823MB/s 19024MB/s
READ: 18968MB/s 19071MB/s
WRITE: 6191.6MB/s 6372.1MB/s
WRITE: 5818.7MB/s 5787.1MB/s
READ: 2011.7MB/s 1981.3MB/s
WRITE: 2011.4MB/s 1980.1MB/s
READ: 1949.3MB/s 1935.7MB/s
WRITE: 1940.4MB/s 1926.1MB/s
jobs6
READ: 21870MB/s 21715MB/s
READ: 19957MB/s 19879MB/s
WRITE: 6528.4MB/s 6537.6MB/s
WRITE: 6098.9MB/s 6073.6MB/s
READ: 2048.6MB/s 2049.9MB/s
WRITE: 2041.7MB/s 2042.9MB/s
READ: 2013.4MB/s 1990.4MB/s
WRITE: 2009.4MB/s 1986.5MB/s
jobs7
READ: 21359MB/s 21124MB/s
READ: 19746MB/s 19293MB/s
WRITE: 6660.4MB/s 6518.8MB/s
WRITE: 6211.6MB/s 6193.1MB/s
READ: 2089.7MB/s 2080.6MB/s
WRITE: 2085.8MB/s 2076.5MB/s
READ: 2041.2MB/s 2052.5MB/s
WRITE: 2037.5MB/s 2048.8MB/s
jobs8
READ: 20477MB/s 19974MB/s
READ: 18922MB/s 18576MB/s
WRITE: 6851.9MB/s 6788.3MB/s
WRITE: 6407.7MB/s 6347.5MB/s
READ: 2134.8MB/s 2136.1MB/s
WRITE: 2132.8MB/s 2134.4MB/s
READ: 2074.2MB/s 2069.6MB/s
WRITE: 2087.3MB/s 2082.4MB/s
jobs9
READ: 19797MB/s 19994MB/s
READ: 18806MB/s 18581MB/s
WRITE: 6878.7MB/s 6822.7MB/s
WRITE: 6456.8MB/s 6447.2MB/s
READ: 2141.1MB/s 2154.7MB/s
WRITE: 2144.4MB/s 2157.3MB/s
READ: 2084.1MB/s 2085.1MB/s
WRITE: 2091.5MB/s 2092.5MB/s
jobs10
READ: 19794MB/s 19784MB/s
READ: 18794MB/s 18745MB/s
WRITE: 6984.4MB/s 6676.3MB/s
WRITE: 6532.3MB/s 6342.7MB/s
READ: 2150.6MB/s 2155.4MB/s
WRITE: 2156.8MB/s 2161.5MB/s
READ: 2106.4MB/s 2095.6MB/s
WRITE: 2109.7MB/s 2098.4MB/s
BASE PATCHED
jobs1 perfstat
stalled-cycles-frontend 102,480,595,419 ( 41.53%) 114,508,864,804 ( 46.92%)
stalled-cycles-backend 51,941,417,832 ( 21.05%) 46,836,112,388 ( 19.19%)
instructions 283,612,054,215 ( 1.15) 283,918,134,959 ( 1.16)
branches 56,372,560,385 ( 724.923) 56,449,814,753 ( 733.766)
branch-misses 374,826,000 ( 0.66%) 326,935,859 ( 0.58%)
jobs2 perfstat
stalled-cycles-frontend 155,142,745,777 ( 40.99%) 164,170,979,198 ( 43.82%)
stalled-cycles-backend 70,813,866,387 ( 18.71%) 66,456,858,165 ( 17.74%)
instructions 463,436,648,173 ( 1.22) 464,221,890,191 ( 1.24)
branches 91,088,733,902 ( 760.088) 91,278,144,546 ( 769.133)
branch-misses 504,460,363 ( 0.55%) 394,033,842 ( 0.43%)
jobs3 perfstat
stalled-cycles-frontend 201,300,397,212 ( 39.84%) 223,969,902,257 ( 44.44%)
stalled-cycles-backend 87,712,593,974 ( 17.36%) 81,618,888,712 ( 16.19%)
instructions 642,869,545,023 ( 1.27) 644,677,354,132 ( 1.28)
branches 125,724,560,594 ( 690.682) 126,133,159,521 ( 694.542)
branch-misses 527,941,798 ( 0.42%) 444,782,220 ( 0.35%)
jobs4 perfstat
stalled-cycles-frontend 246,701,197,429 ( 38.12%) 280,076,030,886 ( 43.29%)
stalled-cycles-backend 119,050,341,112 ( 18.40%) 110,955,641,671 ( 17.15%)
instructions 822,716,962,127 ( 1.27) 825,536,969,320 ( 1.28)
branches 160,590,028,545 ( 688.614) 161,152,996,915 ( 691.068)
branch-misses 650,295,287 ( 0.40%) 550,229,113 ( 0.34%)
jobs5 perfstat
stalled-cycles-frontend 298,958,462,516 ( 38.30%) 344,852,200,358 ( 44.16%)
stalled-cycles-backend 137,558,742,122 ( 17.62%) 129,465,067,102 ( 16.58%)
instructions 1,005,714,688,752 ( 1.29) 1,007,657,999,432 ( 1.29)
branches 195,988,773,962 ( 697.730) 196,446,873,984 ( 700.319)
branch-misses 695,818,940 ( 0.36%) 624,823,263 ( 0.32%)
jobs6 perfstat
stalled-cycles-frontend 334,497,602,856 ( 36.71%) 387,590,419,779 ( 42.38%)
stalled-cycles-backend 163,539,365,335 ( 17.95%) 152,640,193,639 ( 16.69%)
instructions 1,184,738,177,851 ( 1.30) 1,187,396,281,677 ( 1.30)
branches 230,592,915,640 ( 702.902) 231,253,802,882 ( 702.356)
branch-misses 747,934,786 ( 0.32%) 643,902,424 ( 0.28%)
jobs7 perfstat
stalled-cycles-frontend 396,724,684,187 ( 37.71%) 460,705,858,952 ( 43.84%)
stalled-cycles-backend 188,096,616,496 ( 17.88%) 175,785,787,036 ( 16.73%)
instructions 1,364,041,136,608 ( 1.30) 1,366,689,075,112 ( 1.30)
branches 265,253,096,936 ( 700.078) 265,890,524,883 ( 702.839)
branch-misses 784,991,589 ( 0.30%) 729,196,689 ( 0.27%)
jobs8 perfstat
stalled-cycles-frontend 440,248,299,870 ( 36.92%) 509,554,793,816 ( 42.46%)
stalled-cycles-backend 222,575,930,616 ( 18.67%) 213,401,248,432 ( 17.78%)
instructions 1,542,262,045,114 ( 1.29) 1,545,233,932,257 ( 1.29)
branches 299,775,178,439 ( 697.666) 300,528,458,505 ( 694.769)
branch-misses 847,496,084 ( 0.28%) 748,794,308 ( 0.25%)
jobs9 perfstat
stalled-cycles-frontend 506,269,882,480 ( 37.86%) 592,798,032,820 ( 44.43%)
stalled-cycles-backend 253,192,498,861 ( 18.93%) 233,727,666,185 ( 17.52%)
instructions 1,721,985,080,913 ( 1.29) 1,724,666,236,005 ( 1.29)
branches 334,517,360,255 ( 694.134) 335,199,758,164 ( 697.131)
branch-misses 873,496,730 ( 0.26%) 815,379,236 ( 0.24%)
jobs10 perfstat
stalled-cycles-frontend 549,063,363,749 ( 37.18%) 651,302,376,662 ( 43.61%)
stalled-cycles-backend 281,680,986,810 ( 19.07%) 277,005,235,582 ( 18.55%)
instructions 1,901,859,271,180 ( 1.29) 1,906,311,064,230 ( 1.28)
branches 369,398,536,153 ( 694.004) 370,527,696,358 ( 688.409)
branch-misses 967,929,335 ( 0.26%) 890,125,056 ( 0.24%)
BASE PATCHED
seconds elapsed 79.421641008 78.735285546
seconds elapsed 61.471246133 60.869085949
seconds elapsed 62.317058173 62.224188495
seconds elapsed 60.030739363 60.081102518
seconds elapsed 74.070398362 74.317582865
seconds elapsed 84.985953007 85.414364176
seconds elapsed 97.724553255 98.173311344
seconds elapsed 109.488066758 110.268399318
seconds elapsed 122.768189405 122.967164498
seconds elapsed 135.130035105 136.934770801
On my other system (8 x86_64 CPUs, short version of test results):
BASE PATCHED
seconds elapsed 19.518065994 19.806320662
seconds elapsed 15.172772749 15.594718291
seconds elapsed 13.820925970 13.821708564
seconds elapsed 13.293097816 14.585206405
seconds elapsed 16.207284118 16.064431606
seconds elapsed 17.958376158 17.771825767
seconds elapsed 19.478009164 19.602961508
seconds elapsed 21.347152811 21.352318709
seconds elapsed 24.478121126 24.171088735
seconds elapsed 26.865057442 26.767327618
So performance-wise the numbers are quite similar.
Also update zcomp interface to be more aligned with the crypto API.
[1] http://marc.info/?l=linux-kernel&m=144480832108927&w=2
[2] http://marc.info/?l=linux-kernel&m=145379613507518&w=2
[3] https://github.com/sergey-senozhatsky/zram-perf-test
Link: http://lkml.kernel.org/r/20160531122017.2878-3-sergey.senozhatsky@gmail.com
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Suggested-by: Minchan Kim <minchan@kernel.org>
Suggested-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Remove idle streams list and keep compression streams in per-cpu data.
This removes two contented spin_lock()/spin_unlock() calls from write
path and also prevent write OP from being preempted while holding the
compression stream, which can cause slow downs.
For instance, let's assume that we have N cpus and N-2
max_comp_streams.TASK1 owns the last idle stream, TASK2-TASK3 come in
with the write requests:
TASK1 TASK2 TASK3
zram_bvec_write()
spin_lock
find stream
spin_unlock
compress
<<preempted>> zram_bvec_write()
spin_lock
find stream
spin_unlock
no_stream
schedule
zram_bvec_write()
spin_lock
find_stream
spin_unlock
no_stream
schedule
spin_lock
release stream
spin_unlock
wake up TASK2
not only TASK2 and TASK3 will not get the stream, TASK1 will be
preempted in the middle of its operation; while we would prefer it to
finish compression and release the stream.
Test environment: x86_64, 4 CPU box, 3G zram, lzo
The following fio tests were executed:
read, randread, write, randwrite, rw, randrw
with the increasing number of jobs from 1 to 10.
4 streams 8 streams per-cpu
===========================================================
jobs1
READ: 2520.1MB/s 2566.5MB/s 2491.5MB/s
READ: 2102.7MB/s 2104.2MB/s 2091.3MB/s
WRITE: 1355.1MB/s 1320.2MB/s 1378.9MB/s
WRITE: 1103.5MB/s 1097.2MB/s 1122.5MB/s
READ: 434013KB/s 435153KB/s 439961KB/s
WRITE: 433969KB/s 435109KB/s 439917KB/s
READ: 403166KB/s 405139KB/s 403373KB/s
WRITE: 403223KB/s 405197KB/s 403430KB/s
jobs2
READ: 7958.6MB/s 8105.6MB/s 8073.7MB/s
READ: 6864.9MB/s 6989.8MB/s 7021.8MB/s
WRITE: 2438.1MB/s 2346.9MB/s 3400.2MB/s
WRITE: 1994.2MB/s 1990.3MB/s 2941.2MB/s
READ: 981504KB/s 973906KB/s 1018.8MB/s
WRITE: 981659KB/s 974060KB/s 1018.1MB/s
READ: 937021KB/s 938976KB/s 987250KB/s
WRITE: 934878KB/s 936830KB/s 984993KB/s
jobs3
READ: 13280MB/s 13553MB/s 13553MB/s
READ: 11534MB/s 11785MB/s 11755MB/s
WRITE: 3456.9MB/s 3469.9MB/s 4810.3MB/s
WRITE: 3029.6MB/s 3031.6MB/s 4264.8MB/s
READ: 1363.8MB/s 1362.6MB/s 1448.9MB/s
WRITE: 1361.9MB/s 1360.7MB/s 1446.9MB/s
READ: 1309.4MB/s 1310.6MB/s 1397.5MB/s
WRITE: 1307.4MB/s 1308.5MB/s 1395.3MB/s
jobs4
READ: 20244MB/s 20177MB/s 20344MB/s
READ: 17886MB/s 17913MB/s 17835MB/s
WRITE: 4071.6MB/s 4046.1MB/s 6370.2MB/s
WRITE: 3608.9MB/s 3576.3MB/s 5785.4MB/s
READ: 1824.3MB/s 1821.6MB/s 1997.5MB/s
WRITE: 1819.8MB/s 1817.4MB/s 1992.5MB/s
READ: 1765.7MB/s 1768.3MB/s 1937.3MB/s
WRITE: 1767.5MB/s 1769.1MB/s 1939.2MB/s
jobs5
READ: 18663MB/s 18986MB/s 18823MB/s
READ: 16659MB/s 16605MB/s 16954MB/s
WRITE: 3912.4MB/s 3888.7MB/s 6126.9MB/s
WRITE: 3506.4MB/s 3442.5MB/s 5519.3MB/s
READ: 1798.2MB/s 1746.5MB/s 1935.8MB/s
WRITE: 1792.7MB/s 1740.7MB/s 1929.1MB/s
READ: 1727.6MB/s 1658.2MB/s 1917.3MB/s
WRITE: 1726.5MB/s 1657.2MB/s 1916.6MB/s
jobs6
READ: 21017MB/s 20922MB/s 21162MB/s
READ: 19022MB/s 19140MB/s 18770MB/s
WRITE: 3968.2MB/s 4037.7MB/s 6620.8MB/s
WRITE: 3643.5MB/s 3590.2MB/s 6027.5MB/s
READ: 1871.8MB/s 1880.5MB/s 2049.9MB/s
WRITE: 1867.8MB/s 1877.2MB/s 2046.2MB/s
READ: 1755.8MB/s 1710.3MB/s 1964.7MB/s
WRITE: 1750.5MB/s 1705.9MB/s 1958.8MB/s
jobs7
READ: 21103MB/s 20677MB/s 21482MB/s
READ: 18522MB/s 18379MB/s 19443MB/s
WRITE: 4022.5MB/s 4067.4MB/s 6755.9MB/s
WRITE: 3691.7MB/s 3695.5MB/s 5925.6MB/s
READ: 1841.5MB/s 1933.9MB/s 2090.5MB/s
WRITE: 1842.7MB/s 1935.3MB/s 2091.9MB/s
READ: 1832.4MB/s 1856.4MB/s 1971.5MB/s
WRITE: 1822.3MB/s 1846.2MB/s 1960.6MB/s
jobs8
READ: 20463MB/s 20194MB/s 20862MB/s
READ: 18178MB/s 17978MB/s 18299MB/s
WRITE: 4085.9MB/s 4060.2MB/s 7023.8MB/s
WRITE: 3776.3MB/s 3737.9MB/s 6278.2MB/s
READ: 1957.6MB/s 1944.4MB/s 2109.5MB/s
WRITE: 1959.2MB/s 1946.2MB/s 2111.4MB/s
READ: 1900.6MB/s 1885.7MB/s 2082.1MB/s
WRITE: 1896.2MB/s 1881.4MB/s 2078.3MB/s
jobs9
READ: 19692MB/s 19734MB/s 19334MB/s
READ: 17678MB/s 18249MB/s 17666MB/s
WRITE: 4004.7MB/s 4064.8MB/s 6990.7MB/s
WRITE: 3724.7MB/s 3772.1MB/s 6193.6MB/s
READ: 1953.7MB/s 1967.3MB/s 2105.6MB/s
WRITE: 1953.4MB/s 1966.7MB/s 2104.1MB/s
READ: 1860.4MB/s 1897.4MB/s 2068.5MB/s
WRITE: 1858.9MB/s 1895.9MB/s 2066.8MB/s
jobs10
READ: 19730MB/s 19579MB/s 19492MB/s
READ: 18028MB/s 18018MB/s 18221MB/s
WRITE: 4027.3MB/s 4090.6MB/s 7020.1MB/s
WRITE: 3810.5MB/s 3846.8MB/s 6426.8MB/s
READ: 1956.1MB/s 1994.6MB/s 2145.2MB/s
WRITE: 1955.9MB/s 1993.5MB/s 2144.8MB/s
READ: 1852.8MB/s 1911.6MB/s 2075.8MB/s
WRITE: 1855.7MB/s 1914.6MB/s 2078.1MB/s
perf stat
4 streams 8 streams per-cpu
====================================================================================================================
jobs1
stalled-cycles-frontend 23,174,811,209 ( 38.21%) 23,220,254,188 ( 38.25%) 23,061,406,918 ( 38.34%)
stalled-cycles-backend 11,514,174,638 ( 18.98%) 11,696,722,657 ( 19.27%) 11,370,852,810 ( 18.90%)
instructions 73,925,005,782 ( 1.22) 73,903,177,632 ( 1.22) 73,507,201,037 ( 1.22)
branches 14,455,124,835 ( 756.063) 14,455,184,779 ( 755.281) 14,378,599,509 ( 758.546)
branch-misses 69,801,336 ( 0.48%) 80,225,529 ( 0.55%) 72,044,726 ( 0.50%)
jobs2
stalled-cycles-frontend 49,912,741,782 ( 46.11%) 50,101,189,290 ( 45.95%) 32,874,195,633 ( 35.11%)
stalled-cycles-backend 27,080,366,230 ( 25.02%) 27,949,970,232 ( 25.63%) 16,461,222,706 ( 17.58%)
instructions 122,831,629,690 ( 1.13) 122,919,846,419 ( 1.13) 121,924,786,775 ( 1.30)
branches 23,725,889,239 ( 692.663) 23,733,547,140 ( 688.062) 23,553,950,311 ( 794.794)
branch-misses 90,733,041 ( 0.38%) 96,320,895 ( 0.41%) 84,561,092 ( 0.36%)
jobs3
stalled-cycles-frontend 66,437,834,608 ( 45.58%) 63,534,923,344 ( 43.69%) 42,101,478,505 ( 33.19%)
stalled-cycles-backend 34,940,799,661 ( 23.97%) 34,774,043,148 ( 23.91%) 21,163,324,388 ( 16.68%)
instructions 171,692,121,862 ( 1.18) 171,775,373,044 ( 1.18) 170,353,542,261 ( 1.34)
branches 32,968,962,622 ( 628.723) 32,987,739,894 ( 630.512) 32,729,463,918 ( 717.027)
branch-misses 111,522,732 ( 0.34%) 110,472,894 ( 0.33%) 99,791,291 ( 0.30%)
jobs4
stalled-cycles-frontend 98,741,701,675 ( 49.72%) 94,797,349,965 ( 47.59%) 54,535,655,381 ( 33.53%)
stalled-cycles-backend 54,642,609,615 ( 27.51%) 55,233,554,408 ( 27.73%) 27,882,323,541 ( 17.14%)
instructions 220,884,807,851 ( 1.11) 220,930,887,273 ( 1.11) 218,926,845,851 ( 1.35)
branches 42,354,518,180 ( 592.105) 42,362,770,587 ( 590.452) 41,955,552,870 ( 716.154)
branch-misses 138,093,449 ( 0.33%) 131,295,286 ( 0.31%) 121,794,771 ( 0.29%)
jobs5
stalled-cycles-frontend 116,219,747,212 ( 48.14%) 110,310,397,012 ( 46.29%) 66,373,082,723 ( 33.70%)
stalled-cycles-backend 66,325,434,776 ( 27.48%) 64,157,087,914 ( 26.92%) 32,999,097,299 ( 16.76%)
instructions 270,615,008,466 ( 1.12) 270,546,409,525 ( 1.14) 268,439,910,948 ( 1.36)
branches 51,834,046,557 ( 599.108) 51,811,867,722 ( 608.883) 51,412,576,077 ( 729.213)
branch-misses 158,197,086 ( 0.31%) 142,639,805 ( 0.28%) 133,425,455 ( 0.26%)
jobs6
stalled-cycles-frontend 138,009,414,492 ( 48.23%) 139,063,571,254 ( 48.80%) 75,278,568,278 ( 32.80%)
stalled-cycles-backend 79,211,949,650 ( 27.68%) 79,077,241,028 ( 27.75%) 37,735,797,899 ( 16.44%)
instructions 319,763,993,731 ( 1.12) 319,937,782,834 ( 1.12) 316,663,600,784 ( 1.38)
branches 61,219,433,294 ( 595.056) 61,250,355,540 ( 598.215) 60,523,446,617 ( 733.706)
branch-misses 169,257,123 ( 0.28%) 154,898,028 ( 0.25%) 141,180,587 ( 0.23%)
jobs7
stalled-cycles-frontend 162,974,812,119 ( 49.20%) 159,290,061,987 ( 48.43%) 88,046,641,169 ( 33.21%)
stalled-cycles-backend 92,223,151,661 ( 27.84%) 91,667,904,406 ( 27.87%) 44,068,454,971 ( 16.62%)
instructions 369,516,432,430 ( 1.12) 369,361,799,063 ( 1.12) 365,290,380,661 ( 1.38)
branches 70,795,673,950 ( 594.220) 70,743,136,124 ( 597.876) 69,803,996,038 ( 732.822)
branch-misses 181,708,327 ( 0.26%) 165,767,821 ( 0.23%) 150,109,797 ( 0.22%)
jobs8
stalled-cycles-frontend 185,000,017,027 ( 49.30%) 182,334,345,473 ( 48.37%) 99,980,147,041 ( 33.26%)
stalled-cycles-backend 105,753,516,186 ( 28.18%) 107,937,830,322 ( 28.63%) 51,404,177,181 ( 17.10%)
instructions 418,153,161,055 ( 1.11) 418,308,565,828 ( 1.11) 413,653,475,581 ( 1.38)
branches 80,035,882,398 ( 592.296) 80,063,204,510 ( 589.843) 79,024,105,589 ( 730.530)
branch-misses 199,764,528 ( 0.25%) 177,936,926 ( 0.22%) 160,525,449 ( 0.20%)
jobs9
stalled-cycles-frontend 210,941,799,094 ( 49.63%) 204,714,679,254 ( 48.55%) 114,251,113,756 ( 33.96%)
stalled-cycles-backend 122,640,849,067 ( 28.85%) 122,188,553,256 ( 28.98%) 58,360,041,127 ( 17.35%)
instructions 468,151,025,415 ( 1.10) 467,354,869,323 ( 1.11) 462,665,165,216 ( 1.38)
branches 89,657,067,510 ( 585.628) 89,411,550,407 ( 588.990) 88,360,523,943 ( 730.151)
branch-misses 218,292,301 ( 0.24%) 191,701,247 ( 0.21%) 178,535,678 ( 0.20%)
jobs10
stalled-cycles-frontend 233,595,958,008 ( 49.81%) 227,540,615,689 ( 49.11%) 160,341,979,938 ( 43.07%)
stalled-cycles-backend 136,153,676,021 ( 29.03%) 133,635,240,742 ( 28.84%) 65,909,135,465 ( 17.70%)
instructions 517,001,168,497 ( 1.10) 516,210,976,158 ( 1.11) 511,374,038,613 ( 1.37)
branches 98,911,641,329 ( 585.796) 98,700,069,712 ( 591.583) 97,646,761,028 ( 728.712)
branch-misses 232,341,823 ( 0.23%) 199,256,308 ( 0.20%) 183,135,268 ( 0.19%)
per-cpu streams tend to cause significantly less stalled cycles; execute
less branches and hit less branch-misses.
perf stat reported execution time
4 streams 8 streams per-cpu
====================================================================
jobs1
seconds elapsed 20.909073870 20.875670495 20.817838540
jobs2
seconds elapsed 18.529488399 18.720566469 16.356103108
jobs3
seconds elapsed 18.991159531 18.991340812 16.766216066
jobs4
seconds elapsed 19.560643828 19.551323547 16.246621715
jobs5
seconds elapsed 24.746498464 25.221646740 20.696112444
jobs6
seconds elapsed 28.258181828 28.289765505 22.885688857
jobs7
seconds elapsed 32.632490241 31.909125381 26.272753738
jobs8
seconds elapsed 35.651403851 36.027596308 29.108024711
jobs9
seconds elapsed 40.569362365 40.024227989 32.898204012
jobs10
seconds elapsed 44.673112304 43.874898137 35.632952191
Please see
Link: http://marc.info/?l=linux-kernel&m=146166970727530
Link: http://marc.info/?l=linux-kernel&m=146174716719650
for more test results (under low memory conditions).
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Suggested-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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