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Chris; -v1: https://lore.kernel.org/linux-mm/20240620002648.75204-1-21cnbao@gmail.com/ I tested Ryan's RFC patchset[1] and Chris's v3[2] using this v2 tool: [1] https://lore.kernel.org/linux-mm/20240618232648.4090299-1-ryan.roberts@arm.com/ [2] https://lore.kernel.org/linux-mm/20240614-swap-allocator-v2-0-2a513b4a7f2f@kernel.org/ Obviously, we're rarely hitting 100% even in the worst case without "-a" and with "-s," which is good news! If swapin is aligned w/ "-a" and w/o "-s", both Chris's and Ryan's patches show a low fallback ratio though Chris's has the numbers above 0% but Ryan's are 0% (value A). The bad news is that unaligned swapin can significantly increase the fallback ratio, reaching up to 85% for Ryan's patch and 95% for Chris's patchset without "-s." Both approaches approach 100% without "-a" and with "-s" (value B). I believe real workloads should yield a value between A and B. Without "-a," and lacking large folios swap-in, this tool randomly swaps in small folios without considering spatial locality, which is a factor present in real workloads. This typically results in values higher than A and lower than B. Based on the below results, I believe that: 1. We truly require large folio swap-in to achieve comparable results with aligned swap-in(based on the result w/o and w/ "-a") 2. We need a method to prevent small folios from scattering indiscriminately (based on the result "-a -s") * * Test results on Ryan's patchset: * 1. w/ -a ./thp_swap_allocator_test -a Iteration 1: swpout inc: 224, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 2: swpout inc: 231, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 3: swpout inc: 227, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 4: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% ... Iteration 100: swpout inc: 228, swpout fallback inc: 0, Fallback percentage: 0.00% 2. w/o -a ./thp_swap_allocator_test Iteration 1: swpout inc: 208, swpout fallback inc: 25, Fallback percentage: 10.73% Iteration 2: swpout inc: 118, swpout fallback inc: 114, Fallback percentage: 49.14% Iteration 3: swpout inc: 63, swpout fallback inc: 163, Fallback percentage: 72.12% Iteration 4: swpout inc: 45, swpout fallback inc: 178, Fallback percentage: 79.82% Iteration 5: swpout inc: 42, swpout fallback inc: 184, Fallback percentage: 81.42% Iteration 6: swpout inc: 31, swpout fallback inc: 193, Fallback percentage: 86.16% Iteration 7: swpout inc: 27, swpout fallback inc: 201, Fallback percentage: 88.16% Iteration 8: swpout inc: 30, swpout fallback inc: 198, Fallback percentage: 86.84% Iteration 9: swpout inc: 32, swpout fallback inc: 194, Fallback percentage: 85.84% ... Iteration 91: swpout inc: 26, swpout fallback inc: 194, Fallback percentage: 88.18% Iteration 92: swpout inc: 35, swpout fallback inc: 196, Fallback percentage: 84.85% Iteration 93: swpout inc: 33, swpout fallback inc: 191, Fallback percentage: 85.27% Iteration 94: swpout inc: 26, swpout fallback inc: 193, Fallback percentage: 88.13% Iteration 95: swpout inc: 39, swpout fallback inc: 189, Fallback percentage: 82.89% Iteration 96: swpout inc: 28, swpout fallback inc: 196, Fallback percentage: 87.50% Iteration 97: swpout inc: 25, swpout fallback inc: 194, Fallback percentage: 88.58% Iteration 98: swpout inc: 31, swpout fallback inc: 196, Fallback percentage: 86.34% Iteration 99: swpout inc: 32, swpout fallback inc: 202, Fallback percentage: 86.32% Iteration 100: swpout inc: 33, swpout fallback inc: 195, Fallback percentage: 85.53% 3. w/ -a and -s ./thp_swap_allocator_test -a -s Iteration 1: swpout inc: 224, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 2: swpout inc: 218, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 3: swpout inc: 222, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 4: swpout inc: 220, swpout fallback inc: 6, Fallback percentage: 2.65% Iteration 5: swpout inc: 206, swpout fallback inc: 16, Fallback percentage: 7.21% Iteration 6: swpout inc: 233, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 7: swpout inc: 224, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 8: swpout inc: 228, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 9: swpout inc: 217, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 10: swpout inc: 224, swpout fallback inc: 3, Fallback percentage: 1.32% Iteration 11: swpout inc: 211, swpout fallback inc: 12, Fallback percentage: 5.38% Iteration 12: swpout inc: 200, swpout fallback inc: 32, Fallback percentage: 13.79% Iteration 13: swpout inc: 189, swpout fallback inc: 29, Fallback percentage: 13.30% Iteration 14: swpout inc: 195, swpout fallback inc: 31, Fallback percentage: 13.72% Iteration 15: swpout inc: 198, swpout fallback inc: 27, Fallback percentage: 12.00% Iteration 16: swpout inc: 201, swpout fallback inc: 17, Fallback percentage: 7.80% Iteration 17: swpout inc: 206, swpout fallback inc: 6, Fallback percentage: 2.83% Iteration 18: swpout inc: 220, swpout fallback inc: 14, Fallback percentage: 5.98% Iteration 19: swpout inc: 181, swpout fallback inc: 45, Fallback percentage: 19.91% Iteration 20: swpout inc: 223, swpout fallback inc: 8, Fallback percentage: 3.46% Iteration 21: swpout inc: 214, swpout fallback inc: 14, Fallback percentage: 6.14% Iteration 22: swpout inc: 195, swpout fallback inc: 31, Fallback percentage: 13.72% Iteration 23: swpout inc: 223, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 24: swpout inc: 233, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 25: swpout inc: 214, swpout fallback inc: 1, Fallback percentage: 0.47% Iteration 26: swpout inc: 229, swpout fallback inc: 1, Fallback percentage: 0.43% Iteration 27: swpout inc: 214, swpout fallback inc: 5, Fallback percentage: 2.28% Iteration 28: swpout inc: 211, swpout fallback inc: 15, Fallback percentage: 6.64% Iteration 29: swpout inc: 188, swpout fallback inc: 40, Fallback percentage: 17.54% Iteration 30: swpout inc: 207, swpout fallback inc: 18, Fallback percentage: 8.00% Iteration 31: swpout inc: 215, swpout fallback inc: 10, Fallback percentage: 4.44% Iteration 32: swpout inc: 202, swpout fallback inc: 22, Fallback percentage: 9.82% Iteration 33: swpout inc: 223, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 34: swpout inc: 218, swpout fallback inc: 10, Fallback percentage: 4.39% Iteration 35: swpout inc: 203, swpout fallback inc: 30, Fallback percentage: 12.88% Iteration 36: swpout inc: 214, swpout fallback inc: 14, Fallback percentage: 6.14% Iteration 37: swpout inc: 211, swpout fallback inc: 14, Fallback percentage: 6.22% Iteration 38: swpout inc: 193, swpout fallback inc: 28, Fallback percentage: 12.67% Iteration 39: swpout inc: 210, swpout fallback inc: 20, Fallback percentage: 8.70% Iteration 40: swpout inc: 223, swpout fallback inc: 5, Fallback percentage: 2.19% Iteration 41: swpout inc: 224, swpout fallback inc: 7, Fallback percentage: 3.03% Iteration 42: swpout inc: 200, swpout fallback inc: 23, Fallback percentage: 10.31% Iteration 43: swpout inc: 217, swpout fallback inc: 5, Fallback percentage: 2.25% Iteration 44: swpout inc: 206, swpout fallback inc: 18, Fallback percentage: 8.04% Iteration 45: swpout inc: 210, swpout fallback inc: 11, Fallback percentage: 4.98% Iteration 46: swpout inc: 204, swpout fallback inc: 19, Fallback percentage: 8.52% Iteration 47: swpout inc: 228, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 48: swpout inc: 219, swpout fallback inc: 2, Fallback percentage: 0.90% Iteration 49: swpout inc: 212, swpout fallback inc: 6, Fallback percentage: 2.75% Iteration 50: swpout inc: 207, swpout fallback inc: 15, Fallback percentage: 6.76% Iteration 51: swpout inc: 190, swpout fallback inc: 36, Fallback percentage: 15.93% Iteration 52: swpout inc: 212, swpout fallback inc: 17, Fallback percentage: 7.42% Iteration 53: swpout inc: 179, swpout fallback inc: 43, Fallback percentage: 19.37% Iteration 54: swpout inc: 225, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 55: swpout inc: 224, swpout fallback inc: 2, Fallback percentage: 0.88% Iteration 56: swpout inc: 220, swpout fallback inc: 8, Fallback percentage: 3.51% Iteration 57: swpout inc: 203, swpout fallback inc: 25, Fallback percentage: 10.96% Iteration 58: swpout inc: 213, swpout fallback inc: 6, Fallback percentage: 2.74% Iteration 59: swpout inc: 207, swpout fallback inc: 18, Fallback percentage: 8.00% Iteration 60: swpout inc: 216, swpout fallback inc: 14, Fallback percentage: 6.09% Iteration 61: swpout inc: 183, swpout fallback inc: 34, Fallback percentage: 15.67% Iteration 62: swpout inc: 184, swpout fallback inc: 39, Fallback percentage: 17.49% Iteration 63: swpout inc: 184, swpout fallback inc: 39, Fallback percentage: 17.49% Iteration 64: swpout inc: 210, swpout fallback inc: 15, Fallback percentage: 6.67% Iteration 65: swpout inc: 178, swpout fallback inc: 48, Fallback percentage: 21.24% Iteration 66: swpout inc: 188, swpout fallback inc: 30, Fallback percentage: 13.76% Iteration 67: swpout inc: 193, swpout fallback inc: 29, Fallback percentage: 13.06% Iteration 68: swpout inc: 202, swpout fallback inc: 22, Fallback percentage: 9.82% Iteration 69: swpout inc: 213, swpout fallback inc: 5, Fallback percentage: 2.29% Iteration 70: swpout inc: 204, swpout fallback inc: 15, Fallback percentage: 6.85% Iteration 71: swpout inc: 180, swpout fallback inc: 45, Fallback percentage: 20.00% Iteration 72: swpout inc: 210, swpout fallback inc: 21, Fallback percentage: 9.09% Iteration 73: swpout inc: 216, swpout fallback inc: 7, Fallback percentage: 3.14% Iteration 74: swpout inc: 209, swpout fallback inc: 19, Fallback percentage: 8.33% Iteration 75: swpout inc: 222, swpout fallback inc: 7, Fallback percentage: 3.06% Iteration 76: swpout inc: 212, swpout fallback inc: 14, Fallback percentage: 6.19% Iteration 77: swpout inc: 188, swpout fallback inc: 41, Fallback percentage: 17.90% Iteration 78: swpout inc: 198, swpout fallback inc: 17, Fallback percentage: 7.91% Iteration 79: swpout inc: 209, swpout fallback inc: 16, Fallback percentage: 7.11% Iteration 80: swpout inc: 182, swpout fallback inc: 41, Fallback percentage: 18.39% Iteration 81: swpout inc: 217, swpout fallback inc: 1, Fallback percentage: 0.46% Iteration 82: swpout inc: 225, swpout fallback inc: 3, Fallback percentage: 1.32% Iteration 83: swpout inc: 222, swpout fallback inc: 8, Fallback percentage: 3.48% Iteration 84: swpout inc: 201, swpout fallback inc: 21, Fallback percentage: 9.46% Iteration 85: swpout inc: 211, swpout fallback inc: 3, Fallback percentage: 1.40% Iteration 86: swpout inc: 209, swpout fallback inc: 14, Fallback percentage: 6.28% Iteration 87: swpout inc: 181, swpout fallback inc: 42, Fallback percentage: 18.83% Iteration 88: swpout inc: 223, swpout fallback inc: 4, Fallback percentage: 1.76% Iteration 89: swpout inc: 214, swpout fallback inc: 14, Fallback percentage: 6.14% Iteration 90: swpout inc: 192, swpout fallback inc: 33, Fallback percentage: 14.67% Iteration 91: swpout inc: 184, swpout fallback inc: 31, Fallback percentage: 14.42% Iteration 92: swpout inc: 201, swpout fallback inc: 32, Fallback percentage: 13.73% Iteration 93: swpout inc: 181, swpout fallback inc: 40, Fallback percentage: 18.10% Iteration 94: swpout inc: 211, swpout fallback inc: 14, Fallback percentage: 6.22% Iteration 95: swpout inc: 198, swpout fallback inc: 25, Fallback percentage: 11.21% Iteration 96: swpout inc: 205, swpout fallback inc: 22, Fallback percentage: 9.69% Iteration 97: swpout inc: 218, swpout fallback inc: 12, Fallback percentage: 5.22% Iteration 98: swpout inc: 203, swpout fallback inc: 25, Fallback percentage: 10.96% Iteration 99: swpout inc: 218, swpout fallback inc: 12, Fallback percentage: 5.22% Iteration 100: swpout inc: 195, swpout fallback inc: 34, Fallback percentage: 14.85% 4. w/o -a and w/ -s thp_swap_allocator_test -s Iteration 1: swpout inc: 173, swpout fallback inc: 60, Fallback percentage: 25.75% Iteration 2: swpout inc: 85, swpout fallback inc: 147, Fallback percentage: 63.36% Iteration 3: swpout inc: 39, swpout fallback inc: 195, Fallback percentage: 83.33% Iteration 4: swpout inc: 13, swpout fallback inc: 220, Fallback percentage: 94.42% Iteration 5: swpout inc: 10, swpout fallback inc: 215, Fallback percentage: 95.56% Iteration 6: swpout inc: 9, swpout fallback inc: 219, Fallback percentage: 96.05% Iteration 7: swpout inc: 6, swpout fallback inc: 217, Fallback percentage: 97.31% Iteration 8: swpout inc: 6, swpout fallback inc: 215, Fallback percentage: 97.29% Iteration 9: swpout inc: 0, swpout fallback inc: 225, Fallback percentage: 100.00% Iteration 10: swpout inc: 1, swpout fallback inc: 229, Fallback percentage: 99.57% Iteration 11: swpout inc: 2, swpout fallback inc: 216, Fallback percentage: 99.08% Iteration 12: swpout inc: 2, swpout fallback inc: 229, Fallback percentage: 99.13% Iteration 13: swpout inc: 4, swpout fallback inc: 211, Fallback percentage: 98.14% Iteration 14: swpout inc: 1, swpout fallback inc: 221, Fallback percentage: 99.55% Iteration 15: swpout inc: 2, swpout fallback inc: 223, Fallback percentage: 99.11% Iteration 16: swpout inc: 3, swpout fallback inc: 224, Fallback percentage: 98.68% Iteration 17: swpout inc: 2, swpout fallback inc: 231, Fallback percentage: 99.14% ... * * Test results on Chris's v3 patchset: * 1. w/ -a ./thp_swap_allocator_test -a Iteration 1: swpout inc: 224, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 2: swpout inc: 231, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 3: swpout inc: 227, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 4: swpout inc: 217, swpout fallback inc: 5, Fallback percentage: 2.25% Iteration 5: swpout inc: 215, swpout fallback inc: 12, Fallback percentage: 5.29% Iteration 6: swpout inc: 213, swpout fallback inc: 14, Fallback percentage: 6.17% Iteration 7: swpout inc: 207, swpout fallback inc: 15, Fallback percentage: 6.76% Iteration 8: swpout inc: 193, swpout fallback inc: 33, Fallback percentage: 14.60% Iteration 9: swpout inc: 214, swpout fallback inc: 13, Fallback percentage: 5.73% Iteration 10: swpout inc: 199, swpout fallback inc: 25, Fallback percentage: 11.16% Iteration 11: swpout inc: 208, swpout fallback inc: 14, Fallback percentage: 6.31% Iteration 12: swpout inc: 203, swpout fallback inc: 31, Fallback percentage: 13.25% Iteration 13: swpout inc: 192, swpout fallback inc: 25, Fallback percentage: 11.52% Iteration 14: swpout inc: 193, swpout fallback inc: 36, Fallback percentage: 15.72% Iteration 15: swpout inc: 188, swpout fallback inc: 33, Fallback percentage: 14.93% ... It seems Chris's approach can be negatively affected even by aligned swapin, having a low fallback ratio but not 0% while Ryan's patchset hasn't this issue. 2. w/o -a ./thp_swap_allocator_test Iteration 1: swpout inc: 209, swpout fallback inc: 24, Fallback percentage: 10.30% Iteration 2: swpout inc: 100, swpout fallback inc: 132, Fallback percentage: 56.90% Iteration 3: swpout inc: 43, swpout fallback inc: 183, Fallback percentage: 80.97% Iteration 4: swpout inc: 30, swpout fallback inc: 193, Fallback percentage: 86.55% Iteration 5: swpout inc: 21, swpout fallback inc: 205, Fallback percentage: 90.71% Iteration 6: swpout inc: 10, swpout fallback inc: 214, Fallback percentage: 95.54% Iteration 7: swpout inc: 16, swpout fallback inc: 212, Fallback percentage: 92.98% Iteration 8: swpout inc: 9, swpout fallback inc: 219, Fallback percentage: 96.05% Iteration 9: swpout inc: 6, swpout fallback inc: 220, Fallback percentage: 97.35% Iteration 10: swpout inc: 7, swpout fallback inc: 221, Fallback percentage: 96.93% Iteration 11: swpout inc: 7, swpout fallback inc: 222, Fallback percentage: 96.94% Iteration 12: swpout inc: 8, swpout fallback inc: 212, Fallback percentage: 96.36% .. Ryan's fallback ratio(around 85%) seems to be a little better while both are much worse than "-a". 3. w/ -a and -s ./thp_swap_allocator_test -a -s Iteration 1: swpout inc: 224, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 2: swpout inc: 213, swpout fallback inc: 5, Fallback percentage: 2.29% Iteration 3: swpout inc: 215, swpout fallback inc: 7, Fallback percentage: 3.15% Iteration 4: swpout inc: 210, swpout fallback inc: 16, Fallback percentage: 7.08% Iteration 5: swpout inc: 212, swpout fallback inc: 10, Fallback percentage: 4.50% Iteration 6: swpout inc: 215, swpout fallback inc: 18, Fallback percentage: 7.73% Iteration 7: swpout inc: 181, swpout fallback inc: 43, Fallback percentage: 19.20% Iteration 8: swpout inc: 173, swpout fallback inc: 55, Fallback percentage: 24.12% Iteration 9: swpout inc: 163, swpout fallback inc: 54, Fallback percentage: 24.88% Iteration 10: swpout inc: 168, swpout fallback inc: 59, Fallback percentage: 25.99% Iteration 11: swpout inc: 154, swpout fallback inc: 69, Fallback percentage: 30.94% Iteration 12: swpout inc: 166, swpout fallback inc: 66, Fallback percentage: 28.45% Iteration 13: swpout inc: 165, swpout fallback inc: 53, Fallback percentage: 24.31% Iteration 14: swpout inc: 158, swpout fallback inc: 68, Fallback percentage: 30.09% Iteration 15: swpout inc: 168, swpout fallback inc: 57, Fallback percentage: 25.33% Iteration 16: swpout inc: 165, swpout fallback inc: 53, Fallback percentage: 24.31% Iteration 17: swpout inc: 163, swpout fallback inc: 49, Fallback percentage: 23.11% Iteration 18: swpout inc: 172, swpout fallback inc: 62, Fallback percentage: 26.50% Iteration 19: swpout inc: 183, swpout fallback inc: 43, Fallback percentage: 19.03% Iteration 20: swpout inc: 158, swpout fallback inc: 73, Fallback percentage: 31.60% Iteration 21: swpout inc: 147, swpout fallback inc: 81, Fallback percentage: 35.53% Iteration 22: swpout inc: 140, swpout fallback inc: 86, Fallback percentage: 38.05% Iteration 23: swpout inc: 144, swpout fallback inc: 79, Fallback percentage: 35.43% Iteration 24: swpout inc: 132, swpout fallback inc: 101, Fallback percentage: 43.35% Iteration 25: swpout inc: 133, swpout fallback inc: 82, Fallback percentage: 38.14% Iteration 26: swpout inc: 152, swpout fallback inc: 78, Fallback percentage: 33.91% Iteration 27: swpout inc: 138, swpout fallback inc: 81, Fallback percentage: 36.99% Iteration 28: swpout inc: 152, swpout fallback inc: 74, Fallback percentage: 32.74% Iteration 29: swpout inc: 153, swpout fallback inc: 75, Fallback percentage: 32.89% Iteration 30: swpout inc: 151, swpout fallback inc: 74, Fallback percentage: 32.89% ... Chris's approach appears to be more susceptible to negative effects from small folios. 4. w/o -a and w/ -s ./thp_swap_allocator_test -s Iteration 1: swpout inc: 183, swpout fallback inc: 50, Fallback percentage: 21.46% Iteration 2: swpout inc: 75, swpout fallback inc: 157, Fallback percentage: 67.67% Iteration 3: swpout inc: 33, swpout fallback inc: 201, Fallback percentage: 85.90% Iteration 4: swpout inc: 11, swpout fallback inc: 222, Fallback percentage: 95.28% Iteration 5: swpout inc: 10, swpout fallback inc: 215, Fallback percentage: 95.56% Iteration 6: swpout inc: 7, swpout fallback inc: 221, Fallback percentage: 96.93% Iteration 7: swpout inc: 2, swpout fallback inc: 221, Fallback percentage: 99.10% Iteration 8: swpout inc: 4, swpout fallback inc: 217, Fallback percentage: 98.19% Iteration 9: swpout inc: 0, swpout fallback inc: 225, Fallback percentage: 100.00% Iteration 10: swpout inc: 3, swpout fallback inc: 227, Fallback percentage: 98.70% Iteration 11: swpout inc: 1, swpout fallback inc: 217, Fallback percentage: 99.54% Iteration 12: swpout inc: 2, swpout fallback inc: 229, Fallback percentage: 99.13% Iteration 13: swpout inc: 1, swpout fallback inc: 214, Fallback percentage: 99.53% Iteration 14: swpout inc: 2, swpout fallback inc: 220, Fallback percentage: 99.10% Iteration 15: swpout inc: 1, swpout fallback inc: 224, Fallback percentage: 99.56% Iteration 16: swpout inc: 3, swpout fallback inc: 224, Fallback percentage: 98.68% ... Barry Song (1): tools/mm: Introduce a tool to assess swap entry allocation for thp_swapout tools/mm/Makefile | 2 +- tools/mm/thp_swap_allocator_test.c | 233 +++++++++++++++++++++++++++++ 2 files changed, 234 insertions(+), 1 deletion(-) create mode 100644 tools/mm/thp_swap_allocator_test.c -- 2.34.1