On Tue, Apr 05, 2016 at 03:31:09PM +0200, Andreas Herrmann wrote: -8<- > test procedure: > - Create compound cache device > - Test A: fio test using data set 1 (using empty cache > device, it includes creation of data set 1) > - Test B: fio test using data set 1 for the second > successive time > - Test C: fio test using data set 2 (it includes creation > of data set 2) > - Test D: fio test using data set 2 for the second > successive time > - Test E: fio test using data set 2 for the third > successive time > - Test F: fio test using data set 3 (it includes creation > of data set 3) > - Clear cache (remove and recreate caching device, re-attach it to > compound cache device) > - Test G: fio test using data set 1 (using empty cache) > - Copy data set 1 into temporary directory on test disk to clobber > cache > - Test H: fio test using data set 1 (after cache was > clobbered with data from data set 1) > - Test I: fio test using data set 2 (after cache was > clobbered and test H) -8<- > First table shows results for test A, B, C for both dm-cache and > bcache. Remaining tests E-I are shown in second table for dm-cache > and in third table for bcache. > > i = iteration, n = numjobs, shown is bandwidth in KB/s > > | native results| dm-cache | bcache > i | n |1.5TB HD| SSD | test A| test B| test C| test A| test B| test C > ----------------------------------------------------------------------- > 1 | 1 | 353.06 | 20568| 1154.7| 1819.6| 394.79| 351.6| 6111 | 377.2 > 2 | 1 | 348.25 | 20571| 1265.2| 1896.6| 395.46| 701.9| 6393 | 748.8 > 3 | 1 | 352.36 | 20573| 1298.2| 1917.1| 395.05| 1047.3| 6681 | 1120.4 > 4 | 1 | 349.60 | 20542| 1494.5| 1919.2| 394.54| 1389.3| 6962 | 1483.4 > 5 | 1 | 353.02 | 20554| 1703.6| 1921.1| 394.52| 1724.7| 7247 | 1841.7 > 6 | 1 | 352.04 | 20564| 1745.1| 1938.2| 381.38| 2060.1| 7517 | 2200.2 > 7 | 1 | 349.19 | 20585| 1929.5| 1957.6| 399.18| 2383.6| 7805 | 2556.5 > 8 | 1 | 350.14 | 20584| 2047.6| 1935.6| 406.40| 2712.5| 8082 | 2908.5 > 9 | 1 | 348.25 | 20573| 2231.3| 1951.2| 407.63| 3034.3| 8350 | 3260.5 > 10 | 1 | 349.99 | 20579| 2336.2| 2001.7| 403.35| 3355.5| 8622 | 3612.2 > 11 | 2 | 324.67 | 38590| 2904.6| 2643.1| 369.60| 3694.8| 10769 | 3991.5 > 12 | 2 | 327.30 | 38466| 2865.3| 2601.1| 373.93| 4033.4| 11085 | 4369.1 > 13 | 2 | 329.87 | 38550| 2882.2| 2594.9| 382.51| 4371.9| 11395 | 4743.9 > 14 | 2 | 328.70 | 38459| 2893.3| 2614.1| 386.55| 4708.9| 11717 | 5118.6 > 15 | 2 | 324.66 | 38468| 2918.2| 2641.8| 393.40| 5038.3| 12033 | 5491.8 > 16 | 2 | 324.78 | 38514| 2907.8| 2605.4| 400.04| 5379.1| 12336 | 5861.2 > 17 | 2 | 322.55 | 38519| 2923.5| 2684.6| 405.56| 5704.7| 12646 | 6227.9 > 18 | 2 | 325.76 | 38519| 2927.1| 2689.4| 408.50| 6034.9| 12955 | 6585.4 > 19 | 2 | 323.51 | 38482| 3005.5| 2662.3| 411.20| 6360.4| 13263 | 6942.3 > 20 | 2 | 327.49 | 38509| 3016.3| 2714.3| 420.88| 6684.7| 13564 | 7306.2 > 21 | 3 | 337.04 | 56139| 2549.8| 2512.5| 430.07| 5205.9| 12577 | 5659.6 > 22 | 3 | 338.73 | 56210| 2462.2| 2459.1| 428.68| 5542.3| 12899 | 6040.3 > 23 | 3 | 339.08 | 56020| 2442.8| 2519.6| 430.82| 5893.2| 13182 | 6417.4 > 24 | 3 | 340.26 | 56142| 2360.3| 2526.4| 432.77| 6230.7| 13546 | 6796.2 > 25 | 3 | 333.83 | 56081| 2303.1| 2508.4| 434.03| 6571.1| 13865 | 7170.2 > 26 | 3 | 338.32 | 56195| 2344.8| 2508.5| 431.66| 6909.8| 14182 | 7540.5 > 27 | 3 | 339.73 | 56165| 2351.4| 2540.4| 434.86| 7227.1| 14494 | 7915.4 > 28 | 3 | 331.52 | 56216| 2354.5| 2489.7| 430.30| 7570.4| 14812 | 8279.1 > 29 | 3 | 334.47 | 56083| 2339.9| 2490.4| 441.79| 7908.7| 15129 | 8640.6 > 30 | 3 | 347.99 | 56089| 2418.5| 2490.3| 446.06| 8241.4| 15443 | 9008.8 > > | native results| dm-cache > i | n |1.5TB HD| SSD | test D| test E| test F| test G| test H | test I > ------------------------------------------------------------------------ > 1 | 1 | 353.06 | 20568| 461.6 | 521.6 | 390.2 | 328.8| 1098.7 | 222.5 > 2 | 1 | 348.25 | 20571| 466.6 | 524.2 | 389.2 | 184.6| 1093.5 | 229.1 > 3 | 1 | 352.36 | 20573| 485.7 | 521.9 | 389.0 | 480.0| 1095.8 | 225.7 > 4 | 1 | 349.60 | 20542| 497.3 | 525.1 | 389.4 | 579.3| 1096.7 | 230.1 > 5 | 1 | 353.02 | 20554| 501.5 | 527.4 | 388.9 | 649.5| 1100.6 | 226.9 > 6 | 1 | 352.04 | 20564| 504.0 | 528.8 | 369.9 | 714.7| 1095.2 | 224.9 > 7 | 1 | 349.19 | 20585| 507.2 | 530.8 | 398.1 | 766.9| 1095.2 | 225.9 > 8 | 1 | 350.14 | 20584| 497.9 | 530.4 | 402.3 | 817.1| 1096.6 | 226.5 > 9 | 1 | 348.25 | 20573| 516.6 | 535.7 | 399.5 | 847.7| 1098.2 | 226.8 > 10 | 1 | 349.99 | 20579| 518.1 | 534.2 | 397.1 | 877.8| 1098.7 | 232.6 > 11 | 2 | 324.67 | 38590| 449.8 | 472.9 | 373.4 | 888.7| 1201.1 | 261.1 > 12 | 2 | 327.30 | 38466| 447.3 | 473.0 | 377.1 | 898.9| 1205.7 | 265.9 > 13 | 2 | 329.87 | 38550| 451.9 | 473.9 | 386.3 | 932.4| 1204.1 | 264.9 > 14 | 2 | 328.70 | 38459| 451.0 | 475.0 | 394.9 | 961.1| 1205.3 | 265.7 > 15 | 2 | 324.66 | 38468| 456.5 | 476.6 | 401.2 | 993.7| 1210.7 | 268.6 > 16 | 2 | 324.78 | 38514| 459.4 | 487.0 | 409.0 | 1034.9| 1206.2 | 269.7 > 17 | 2 | 322.55 | 38519| 456.1 | 498.9 | 411.7 | 1062.3| 1204.9 | 273.3 > 18 | 2 | 325.76 | 38519| 458.3 | 500.2 | 422.0 | 1081.6| 1204.6 | 280.5 > 19 | 2 | 323.51 | 38482| 457.1 | 498.3 | 430.5 | 1100.3| 1207.5 | 279.0 > 20 | 2 | 327.49 | 38509| 455.8 | 500.4 | 428.7 | 1106.8| 1203.6 | 285.7 > 21 | 3 | 337.04 | 56139| 462.6 | 481.5 | 439.0 | 1060.9| 1250.2 | 312.7 > 22 | 3 | 338.73 | 56210| 462.9 | 483.3 | 437.2 | 1095.7| 1253.9 | 306.8 > 23 | 3 | 339.08 | 56020| 469.5 | 489.1 | 437.8 | 1163.7| 1248.9 | 304.7 > 24 | 3 | 340.26 | 56142| 462.1 | 487.1 | 440.1 | 1189.9| 1252.1 | 303.0 > 25 | 3 | 333.83 | 56081| 465.1 | 490.8 | 436.9 | 1217.7| 1248.6 | 302.6 > 26 | 3 | 338.32 | 56195| 465.1 | 489.8 | 433.4 | 1234.8| 1248.7 | 308.3 > 27 | 3 | 339.73 | 56165| 464.6 | 490.7 | 437.0 | 1256.1| 1253.3 | 305.4 > 28 | 3 | 331.52 | 56216| 463.2 | 496.7 | 435.6 | 1281.8| 1250.5 | 307.1 > 29 | 3 | 334.47 | 56083| 469.4 | 493.3 | 434.6 | 1302.6| 1249.4 | 308.9 > 30 | 3 | 347.99 | 56089| 464.0 | 501.4 | 442.5 | 1321.5| 1250.9 | 305.4 Potential issue 1: It's hard to get data replaced (slow promotion/demotion) in the cache. Illustrated by comparing results for tests A+B with what happened for tests C+D. Same action, creating a bunch of test files, then doing random read accesses and run a subsequent test with same set of data files. But once it was done with an empty cache (tests A+B) and one time with an already fully utilized cache (tests C+D). And even doing a third round with the second data set (test E) doesn't substantially improve performance. Potential issue 2: The very last test on the list -- test I -- showed performance that was significantly below performance of the backing device. Regards, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
