add chunksize cheat-sheet

docs/chunksizes.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+
+# there's far better ways to do this but its 4am and i dont wanna think
+
+# just pypy it my dude
+
+import math
+
+def humansize(sz, terse=False):
+    for unit in ["B", "KiB", "MiB", "GiB", "TiB"]:
+        if sz < 1024:
+            break
+
+        sz /= 1024.0
+
+    ret = " ".join([str(sz)[:4].rstrip("."), unit])
+
+    if not terse:
+        return ret
+
+    return ret.replace("iB", "").replace(" ", "")
+
+
+def up2k_chunksize(filesize):
+    chunksize = 1024 * 1024
+    stepsize = 512 * 1024
+    while True:
+        for mul in [1, 2]:
+            nchunks = math.ceil(filesize * 1.0 / chunksize)
+            if nchunks <= 256 or (chunksize >= 32 * 1024 * 1024 and nchunks <= 4096):
+                return chunksize
+
+            chunksize += stepsize
+            stepsize *= mul
+
+
+def main():
+    prev = 1048576
+    n = n0 = 524288
+    while True:
+        csz = up2k_chunksize(n)
+        if csz > prev:
+            print(f"| {n-n0:>18_} | {humansize(n-n0):>8} | {prev:>13_} | {humansize(prev):>8} |".replace("_", " "))
+            prev = csz
+        n += n0
+
+
+main()