** Description changed:
+ --- initramfs-tools
+
+ [Impact]
+
+ * Initramfs-tools already supports compressed kernel modules. However,
+ in focal it does so inefficiently. It is always better to have a
+ compressed initramfs of uncommpressed kernel modules, than a compressed
+ initrd of compressed kernel modules. Thus when kernel module compression
+ is turned on, it is prudent for initramfs-tools to pre-uncompress kernel
+ modules when building initramfs.
+
+ [Test Plan]
+
+ * Compress all kernel modules with xz for a current kernel, check that
+ all of them have .ko.xz extension and no .ko ones available
+
+ * Rerun depmod
+
+ * Update initramfs with update-initramfs -u
+
+ * lsinitramfs contents and check that all kernel modules are present,
+ and are uncompressed (.ko extension)
+
+ [Where problems could occur]
+
+ * This optimization for compressed kernel modules will make initramfs
+ build time longer (due to decompression) whilst improving bootspeed
+ (overall smaller size of the initrd).
+
+ [Other Info]
+
+ * Original bug report re kernel feature
+
+
Symbol: MODULE_COMPRESS_ZSTD [=n]
Type : bool
= Impacts to measure and observe =
== Disk space ==
* Inspect linux-modules-* and linux-modules-extra* deb package
Installed-Size and Download-Size changes, i.e.
$ apt show linux-modules-5.8.0-53-generic linux-modules-
extra-5.8.0-53-generic | grep -e Package: -e Size:
Package: linux-modules-5.8.0-53-generic
Installed-Size: 81.5 MB
Download-Size: 15.5 MB
Package: linux-modules-extra-5.8.0-53-generic
Installed-Size: 215 MB
Download-Size: 41.5 MB
In theory, there should not be a significant change in the Download-
size. It is desired that there is a significant reduction in Installed-
Size. Modules take up about 300MB and normally one has upto three kernel
version installed, resulting in about of 1GB of disk space that one
constantly pays for.
== Boot Speed ==
In theory, boot speed may either improve or regress. It depends if disk
IO is slower than decompression speed, meaning loading compressed
modules is faster.
Also one has to observe the changes in the initrd size. zstd(zstd)
compression may result in slight growth, which shouldn't impact boot
speed too much.
= Outcomes =
If installed size savings can be achieved without regressing bootspeed
we should enable CONFIG_MODULE_COMPRESS_ZSTD=y by default.
** Description changed:
--- initramfs-tools
[Impact]
- * Initramfs-tools already supports compressed kernel modules. However,
+ * Initramfs-tools already supports compressed kernel modules. However,
in focal it does so inefficiently. It is always better to have a
compressed initramfs of uncommpressed kernel modules, than a compressed
initrd of compressed kernel modules. Thus when kernel module compression
is turned on, it is prudent for initramfs-tools to pre-uncompress kernel
modules when building initramfs.
[Test Plan]
- * Compress all kernel modules with xz for a current kernel, check that
+ * Compress all kernel modules with xz for a current kernel, check that
all of them have .ko.xz extension and no .ko ones available
- * Rerun depmod
+ * Rerun depmod
- * Update initramfs with update-initramfs -u
+ * Update initramfs with update-initramfs -u
- * lsinitramfs contents and check that all kernel modules are present,
+ * lsinitramfs contents and check that all kernel modules are present,
and are uncompressed (.ko extension)
[Where problems could occur]
- * This optimization for compressed kernel modules will make initramfs
+ * This optimization for compressed kernel modules will make initramfs
build time longer (due to decompression) whilst improving bootspeed
(overall smaller size of the initrd).
[Other Info]
-
- * Original bug report re kernel feature
+ * Original bug report re kernel feature
+
+ --- linux
Symbol: MODULE_COMPRESS_ZSTD [=n]
Type : bool
= Impacts to measure and observe =
== Disk space ==
* Inspect linux-modules-* and linux-modules-extra* deb package
Installed-Size and Download-Size changes, i.e.
$ apt show linux-modules-5.8.0-53-generic linux-modules-
extra-5.8.0-53-generic | grep -e Package: -e Size:
Package: linux-modules-5.8.0-53-generic
Installed-Size: 81.5 MB
Download-Size: 15.5 MB
Package: linux-modules-extra-5.8.0-53-generic
Installed-Size: 215 MB
Download-Size: 41.5 MB
In theory, there should not be a significant change in the Download-
size. It is desired that there is a significant reduction in Installed-
Size. Modules take up about 300MB and normally one has upto three kernel
version installed, resulting in about of 1GB of disk space that one
constantly pays for.
== Boot Speed ==
In theory, boot speed may either improve or regress. It depends if disk
IO is slower than decompression speed, meaning loading compressed
modules is faster.
Also one has to observe the changes in the initrd size. zstd(zstd)
compression may result in slight growth, which shouldn't impact boot
speed too much.
= Outcomes =
If installed size savings can be achieved without regressing bootspeed
we should enable CONFIG_MODULE_COMPRESS_ZSTD=y by default.
** Also affects: initramfs-tools (Ubuntu Impish)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Impish)
Importance: Undecided
Status: New
** Also affects: initramfs-tools (Ubuntu Jammy)
Importance: Undecided
Status: Fix Released
** Also affects: linux (Ubuntu Jammy)
Importance: Medium
Assignee: Dimitri John Ledkov (xnox)
Status: In Progress
** Also affects: initramfs-tools (Ubuntu Focal)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Focal)
Importance: Undecided
Status: New
** No longer affects: linux (Ubuntu Impish)
** No longer affects: linux (Ubuntu Focal)
** Summary changed:
- Benchmark if we can compress kernel modules
+ Support compressed kernel modules in initramfs-tools and kernel
** Description changed:
--- initramfs-tools
[Impact]
* Initramfs-tools already supports compressed kernel modules. However,
- in focal it does so inefficiently. It is always better to have a
- compressed initramfs of uncommpressed kernel modules, than a compressed
- initrd of compressed kernel modules. Thus when kernel module compression
- is turned on, it is prudent for initramfs-tools to pre-uncompress kernel
- modules when building initramfs.
+ in focal and impish it does so inefficiently. It is always better to
+ have a compressed initramfs of uncommpressed kernel modules, than a
+ compressed initrd of compressed kernel modules. Thus when kernel module
+ compression is turned on, it is prudent for initramfs-tools to pre-
+ uncompress kernel modules when building initramfs.
[Test Plan]
* Compress all kernel modules with xz for a current kernel, check that
all of them have .ko.xz extension and no .ko ones available
* Rerun depmod
* Update initramfs with update-initramfs -u
* lsinitramfs contents and check that all kernel modules are present,
and are uncompressed (.ko extension)
[Where problems could occur]
* This optimization for compressed kernel modules will make initramfs
build time longer (due to decompression) whilst improving bootspeed
(overall smaller size of the initrd).
[Other Info]
* Original bug report re kernel feature
--- linux
Symbol: MODULE_COMPRESS_ZSTD [=n]
Type : bool
= Impacts to measure and observe =
== Disk space ==
* Inspect linux-modules-* and linux-modules-extra* deb package
Installed-Size and Download-Size changes, i.e.
$ apt show linux-modules-5.8.0-53-generic linux-modules-
extra-5.8.0-53-generic | grep -e Package: -e Size:
Package: linux-modules-5.8.0-53-generic
Installed-Size: 81.5 MB
Download-Size: 15.5 MB
Package: linux-modules-extra-5.8.0-53-generic
Installed-Size: 215 MB
Download-Size: 41.5 MB
In theory, there should not be a significant change in the Download-
size. It is desired that there is a significant reduction in Installed-
Size. Modules take up about 300MB and normally one has upto three kernel
version installed, resulting in about of 1GB of disk space that one
constantly pays for.
== Boot Speed ==
In theory, boot speed may either improve or regress. It depends if disk
IO is slower than decompression speed, meaning loading compressed
modules is faster.
Also one has to observe the changes in the initrd size. zstd(zstd)
compression may result in slight growth, which shouldn't impact boot
speed too much.
= Outcomes =
If installed size savings can be achieved without regressing bootspeed
we should enable CONFIG_MODULE_COMPRESS_ZSTD=y by default.
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/1932329
Title:
Support compressed kernel modules in initramfs-tools and kernel
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/initramfs-tools/+bug/1932329/+subscriptions
--
ubuntu-bugs mailing list
ubuntu-bugs@lists.ubuntu.com
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
