From 5e90a99dfdcc0a16f52213370cda29779571e36c Mon Sep 17 00:00:00 2001
From: eunhhu <necpition205@gmail.com>
Date: Sun, 27 Sep 2026 13:57:51 +0100
Subject: Measure whether sharding owners by key would add writes (084)

It would not, on this device. One file's syncs or four at once, the SD card
completes the same 510-690 commits per second, the latency growing with the
number of files. The scoreboard app with two owners, each with a store of
its own, took 23% fewer durable posts than one owner (median 16,230 against
20,974 a second) with 2-3x the p99: syncs queue, and each carries half the
events. One owner's group commit stays; cores serve reads, and writes grow
by making the sync itself cheaper.
---
 .../2026-09-27-ext4-linux-aarch64.json             | 192 +++++++++++++++++++++
 1 file changed, 192 insertions(+)
 create mode 100644 research/experiments/013-parallel-syncs/2026-09-27-ext4-linux-aarch64.json

(limited to 'research/experiments/013-parallel-syncs/2026-09-27-ext4-linux-aarch64.json')

diff --git a/research/experiments/013-parallel-syncs/2026-09-27-ext4-linux-aarch64.json b/research/experiments/013-parallel-syncs/2026-09-27-ext4-linux-aarch64.json
new file mode 100644
index 0000000..14d57e4
--- /dev/null
+++ b/research/experiments/013-parallel-syncs/2026-09-27-ext4-linux-aarch64.json
@@ -0,0 +1,192 @@
+{
+ "rounds": [
+  {
+   "probe": [
+    {
+     "threads": 1,
+     "bytes": 4096,
+     "commits": 1920,
+     "commits_per_second": 637.7,
+     "p50_ms": 1.22,
+     "p90_ms": 1.58,
+     "p99_ms": 11.27
+    },
+    {
+     "threads": 2,
+     "bytes": 4096,
+     "commits": 2026,
+     "commits_per_second": 663.6,
+     "p50_ms": 2.43,
+     "p90_ms": 3.24,
+     "p99_ms": 21.53
+    },
+    {
+     "threads": 4,
+     "bytes": 4096,
+     "commits": 1882,
+     "commits_per_second": 626.1,
+     "p50_ms": 5.09,
+     "p90_ms": 7.88,
+     "p99_ms": 59.99
+    }
+   ],
+   "app": [
+    {
+     "owners": 1,
+     "posts_per_second": 22275.0,
+     "p50_us": 2176,
+     "p99_us": 13824,
+     "errors": 0
+    },
+    {
+     "owners": 2,
+     "posts_per_second": 16833.333333333332,
+     "p50_us": 2432,
+     "p99_us": 55296,
+     "errors": 0
+    }
+   ]
+  },
+  {
+   "probe": [
+    {
+     "threads": 2,
+     "bytes": 4096,
+     "commits": 1695,
+     "commits_per_second": 564.7,
+     "p50_ms": 2.44,
+     "p90_ms": 4.6,
+     "p99_ms": 55.87
+    },
+    {
+     "threads": 4,
+     "bytes": 4096,
+     "commits": 1971,
+     "commits_per_second": 655.9,
+     "p50_ms": 5.06,
+     "p90_ms": 7.79,
+     "p99_ms": 58.39
+    },
+    {
+     "threads": 1,
+     "bytes": 4096,
+     "commits": 2006,
+     "commits_per_second": 668.6,
+     "p50_ms": 1.21,
+     "p90_ms": 1.57,
+     "p99_ms": 4.7
+    }
+   ],
+   "app": [
+    {
+     "owners": 2,
+     "posts_per_second": 17716.333333333332,
+     "p50_us": 2560,
+     "p99_us": 36864,
+     "errors": 0
+    },
+    {
+     "owners": 1,
+     "posts_per_second": 23384.333333333332,
+     "p50_us": 2176,
+     "p99_us": 14336,
+     "errors": 0
+    }
+   ]
+  },
+  {
+   "probe": [
+    {
+     "threads": 4,
+     "bytes": 4096,
+     "commits": 2056,
+     "commits_per_second": 684.3,
+     "p50_ms": 4.93,
+     "p90_ms": 7.68,
+     "p99_ms": 35.01
+    },
+    {
+     "threads": 1,
+     "bytes": 4096,
+     "commits": 1536,
+     "commits_per_second": 511.6,
+     "p50_ms": 1.23,
+     "p90_ms": 3.07,
+     "p99_ms": 12.52
+    },
+    {
+     "threads": 2,
+     "bytes": 4096,
+     "commits": 1692,
+     "commits_per_second": 556.2,
+     "p50_ms": 2.45,
+     "p90_ms": 4.57,
+     "p99_ms": 53.54
+    }
+   ],
+   "app": [
+    {
+     "owners": 1,
+     "posts_per_second": 18541.666666666668,
+     "p50_us": 2304,
+     "p99_us": 25600,
+     "errors": 0
+    },
+    {
+     "owners": 2,
+     "posts_per_second": 13991.333333333334,
+     "p50_us": 2560,
+     "p99_us": 57344,
+     "errors": 0
+    }
+   ]
+  },
+  {
+   "probe": [
+    {
+     "threads": 1,
+     "bytes": 4096,
+     "commits": 1981,
+     "commits_per_second": 660.2,
+     "p50_ms": 1.21,
+     "p90_ms": 1.57,
+     "p99_ms": 4.0
+    },
+    {
+     "threads": 2,
+     "bytes": 4096,
+     "commits": 1994,
+     "commits_per_second": 664.4,
+     "p50_ms": 2.42,
+     "p90_ms": 3.2,
+     "p99_ms": 20.6
+    },
+    {
+     "threads": 4,
+     "bytes": 4096,
+     "commits": 2011,
+     "commits_per_second": 669.8,
+     "p50_ms": 4.96,
+     "p90_ms": 7.96,
+     "p99_ms": 41.8
+    }
+   ],
+   "app": [
+    {
+     "owners": 2,
+     "posts_per_second": 15627.0,
+     "p50_us": 2432,
+     "p99_us": 47104,
+     "errors": 0
+    },
+    {
+     "owners": 1,
+     "posts_per_second": 19672.333333333332,
+     "p50_us": 2304,
+     "p99_us": 16384,
+     "errors": 0
+    }
+   ]
+  }
+ ]
+}
-- 
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