sizes: change minimal install size recommendations

Remove swap space size allocation suggestion.  It often won't be used on
smaller installs anyhow.
Drop /boot size to the min instead of max.
Add esp size min into the mix.
(which more than cancels out the /boot change to min)
Reduce padding to max(2G, 50% source min)

subiquity/common/filesystem/sizes.py

@@ -16,7 +16,6 @@
 import math
 
 import attr
-from curtin import swap
 
 from subiquity.common.types import GuidedResizeValues
 from subiquity.models.filesystem import GiB, MiB, align_down, align_up
@@ -119,24 +118,17 @@ def calculate_guided_resize(
 # 2) Room for boot - we employ a scaling system to help select the recommended
 #    size of a dedicated /boot and/or efi system partition (see above).  If
 #    /boot is not actually a separate partition, this space needs to be
-#    accounted for as part of the planned rootfs size.  The files that would
-#    otherwise be stored in a dedicated UEFI partition are presumed to be
-#    negligible on non-UEFI systems.  As /boot itself uses a scaling sizing
-#    system, use the bootfs_scale.maximum value for the purposes of finding
-#    minimum suggested size.  The maximum value is to be used instead of the
-#    minimum as the boot scaling system will also make adjustments, and we
-#    don’t want to short change the other calculations.
-# 3) Room to grow - while meaningful work can sometimes be possible on a full
+#    accounted for as part of the planned rootfs size.
+# 3) room for esp - similar to boot.  Included in all calculations, even if
+#    we're not UEFI boot.
+# 4) Room to grow - while meaningful work can sometimes be possible on a full
 #    disk, it’s not the sort of thing to suggest in a guided install.
-#    Suggest for room to grow max(2GiB, 80% of source minimum).
-# 4) Swap - Ubuntu policy recommends swap, either in the form of a partition or
-#    a swapfile.  Curtin has an existing swap size recommendation at
-#    curtin.swap.suggested_swapsize().
+#    Suggest for room to grow max(2GiB, 50% of source minimum).
 def calculate_suggested_install_min(source_min: int, part_align: int = MiB) -> int:
-    room_for_boot = bootfs_scale.maximum
-    room_to_grow = max(2 * GiB, math.ceil(0.8 * source_min))
-    room_for_swap = swap.suggested_swapsize()
-    total = source_min + room_for_boot + room_to_grow + room_for_swap
+    room_for_boot = bootfs_scale.minimum
+    room_for_esp = uefi_scale.minimum
+    room_to_grow = max(2 * GiB, math.ceil(0.5 * source_min))
+    total = source_min + room_for_boot + room_for_esp + room_to_grow
     return align_up(total, part_align)
 
 

subiquity/common/filesystem/tests/test_sizes.py

@@ -140,37 +140,29 @@ class TestCalculateGuidedResize(unittest.TestCase):
 
 
 class TestCalculateInstallMin(unittest.TestCase):
-    @mock.patch("subiquity.common.filesystem.sizes.swap.suggested_swapsize")
+    @mock.patch("subiquity.common.filesystem.sizes.uefi_scale")
     @mock.patch("subiquity.common.filesystem.sizes.bootfs_scale")
-    def test_small_setups(self, bootfs_scale, swapsize):
-        swapsize.return_value = 1 << 30
-        bootfs_scale.maximum = 1 << 30
+    def test_small_setups(self, bootfs_scale, uefi_scale):
+        uefi_scale.minimum = 1 << 30
+        bootfs_scale.minimum = 1 << 30
         source_min = 1 << 30
         # with a small source, we hit the default 2GiB padding
         self.assertEqual(5 << 30, calculate_suggested_install_min(source_min))
 
-    @mock.patch("subiquity.common.filesystem.sizes.swap.suggested_swapsize")
+    @mock.patch("subiquity.common.filesystem.sizes.uefi_scale")
     @mock.patch("subiquity.common.filesystem.sizes.bootfs_scale")
-    def test_small_setups_big_swap(self, bootfs_scale, swapsize):
-        swapsize.return_value = 10 << 30
-        bootfs_scale.maximum = 1 << 30
+    def test_small_setups_big_boot(self, bootfs_scale, uefi_scale):
+        uefi_scale.minimum = 1 << 30
+        bootfs_scale.minimum = 10 << 30
         source_min = 1 << 30
         self.assertEqual(14 << 30, calculate_suggested_install_min(source_min))
 
-    @mock.patch("subiquity.common.filesystem.sizes.swap.suggested_swapsize")
+    @mock.patch("subiquity.common.filesystem.sizes.uefi_scale")
     @mock.patch("subiquity.common.filesystem.sizes.bootfs_scale")
-    def test_small_setups_big_boot(self, bootfs_scale, swapsize):
-        swapsize.return_value = 1 << 30
-        bootfs_scale.maximum = 10 << 30
-        source_min = 1 << 30
-        self.assertEqual(14 << 30, calculate_suggested_install_min(source_min))
-
-    @mock.patch("subiquity.common.filesystem.sizes.swap.suggested_swapsize")
-    @mock.patch("subiquity.common.filesystem.sizes.bootfs_scale")
-    def test_big_source(self, bootfs_scale, swapsize):
-        swapsize.return_value = 1 << 30
-        bootfs_scale.maximum = 2 << 30
+    def test_big_source(self, bootfs_scale, uefi_scale):
+        uefi_scale.minimum = 1 << 30
+        bootfs_scale.minimum = 2 << 30
         source_min = 10 << 30
-        # a bigger source should hit 80% padding
-        expected = (10 + 8 + 1 + 2) << 30
+        # a bigger source should hit 50% padding
+        expected = (10 + 5 + 1 + 2) << 30
         self.assertEqual(expected, calculate_suggested_install_min(source_min))