Re: [PATCH] enforce function inlining for hot functions

From: Andrew Morton
Date: Fri Apr 24 2015 - 15:49:13 EST

On Thu, 23 Apr 2015 23:40:01 +0200 Hagen Paul Pfeifer <hagen@xxxxxxxx> wrote:

> GCC inlining heuristics are sometimes quizzical. Especially with inline
> assembler constructs GCC seems to have issues. A allyesconfig show a rather
> long list of functions where GCC inlining decisions are questionable (not
> inlined).

I can't reproduce this with either gcc-4.8.2 or gcc-4.4.4. The patch
makes zero difference to `size vmlinux' and a bit of poking around with
nm doesn't show any out-of-lined versions of the functions you

So. More details, please. How to demonstrate this, gcc versions, etc.

> Furthermore, because the functions are declared with static
> linkage each function is copied n times - and n can be rather high:
> atomic_inc: 544 duplicates
> rcu_read_unlock: 453 duplicates
> rcu_read_lock: 383 duplicates
> get_dma_ops: 271 duplicates
> arch_local_irq_restore: 258 duplicates
> atomic_dec: 215 duplicates
> kzalloc: 185 duplicates
> cpumask_check: 157 duplicates
> test_and_set_bit: 156 duplicates
> cpumask_next: 146 duplicates
> list_del: 131 duplicates
> kref_get: 126 duplicates

That's pretty pathetic.
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