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start [2017-01-21 22:38] joshtriplett Add note about nm --size-sort. |
start [2020-07-06 21:25] joshtriplett Drop mention of CONFIG_EMBEDDED, and explain use of CONFIG_EXPERT. |
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| ====== Building a tiny kernel ====== | ====== Building a tiny kernel ====== | ||
| - | With Linux 3.17-rc1 and newer, ''make tinyconfig'' will produce a minimal kernel. You can then turn on the minimal set of options you need. | + | With current Linux (since 3.17-rc1 and newer, ''make tinyconfig'' will produce a minimal kernel. You can then turn on the minimal set of options you need. |
| - | + | ||
| - | On previous kernels, you'll need to take a few additional steps to make the kernel as small as possible: | + | |
| - | + | ||
| - | * Prior to 3.15-rc1, ''make allnoconfig'' did not turn off options behind CONFIG_EXPERT or CONFIG_EMBEDDED, so you'll have to do so manually. | + | |
| - | * Change the allocator from SLUB to SLOB | + | |
| - | * Change the kernel compression method from GZIP to XZ | + | |
| - | * Disable HIGHMEM4G, using NOHIGHMEM instead | + | |
| - | * Set ''CONFIG_OPTIMIZE_INLINING=y'' | + | |
| - | * Set ''CONFIG_CC_OPTIMIZE_FOR_SIZE=y'' | + | |
| You'll want to target the most code-size-efficient architecture supported by your target machine; for instance, on x86 systems, build a 32-bit kernel rather than a 64-bit kernel. On current kernels, ''make allnoconfig'' should do this automatically. | You'll want to target the most code-size-efficient architecture supported by your target machine; for instance, on x86 systems, build a 32-bit kernel rather than a 64-bit kernel. On current kernels, ''make allnoconfig'' should do this automatically. | ||
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| When submitting a change to make the kernel smaller, use ''scripts/bloat-o-meter'' to compare the size of the old and new vmlinux, overall and broken out by symbol. Include the bloat-o-meter output in your commit message. | When submitting a change to make the kernel smaller, use ''scripts/bloat-o-meter'' to compare the size of the old and new vmlinux, overall and broken out by symbol. Include the bloat-o-meter output in your commit message. | ||
| - | Most new configuration options added as part of this effort should depend on CONFIG_EMBEDDED or CONFIG_EXPERT. | + | When introducing a new configuration option for an existing kernel feature, the new option should likely depend on CONFIG_EXPERT. |
| If your changes affect the size of the decompression stub, you may additionally need to run bloat-o-meter on the stub. | If your changes affect the size of the decompression stub, you may additionally need to run bloat-o-meter on the stub. | ||
start.txt · Last modified: 2020-07-06 21:27 by joshtriplett
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