Messages in this thread | | | From | Rasmus Villemoes <> | Subject | [PATCH 0/5] kernel/cpu.c: eliminate some indirection | Date | Fri, 25 Sep 2015 20:22:22 +0200 |
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Maybe third time's the charm...
The four cpumasks cpu_{possible,online,present,active}_bits are exposed readonly via the corresponding const variables cpu_xyz_mask. But they are also accessible for arbitrary writing via the exposed functions set_cpu_xyz. There's quite a bit of code throughout the kernel which iterates over or otherwise accesses these bitmaps, and having the access go via the cpu_xyz_mask variables is simply a useless indirection.
It may be that any problem in CS can be solved by an extra level of indirection, but that doesn't mean every extra indirection solves a problem. In this case, it even necessitates some minor ugliness (see 3/5).
The first four patches eliminate the cpu_xyz_mask variables by simply exposing the actual bitmaps, after renaming them to discourage direct access - that still happens through cpu_xyz_mask, which are now simply macros with the same type and value as they used to have.
After that, there's no longer any reason to have the setter functions be out-of-line: The boolean parameter is almost always a literal true or false, so by making them static inlines they will usually compile to one or two instructions.
For a defconfig build, bloat-o-meter says we save ~3000 bytes.
Rasmus Villemoes (5): kernel/cpu.c: change type of cpu_possible_bits and friends kernel/cpu.c: export __cpu_*_mask drivers/base/cpu.c: use __cpu_*_mask directly kernel/cpu.c: eliminate cpu_*_mask kernel/cpu.c: make set_cpu_* static inlines
drivers/base/cpu.c | 10 ++++---- include/linux/cpumask.h | 55 +++++++++++++++++++++++++++++++++++------- kernel/cpu.c | 64 ++++++++++--------------------------------------- 3 files changed, 65 insertions(+), 64 deletions(-)
-- 2.1.3
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