Another attempt to remove this intermediate allocator. ;-)
I didn't think I would like this approach before I started to look at
doing this patch, but now I think I rather like it!
The first patch uses an inline function (alloc_node()) to implement the
allocators, redefining the macro to declare the allocators to, basically:
static struct alloc_state something_state;
return alloc_node(&something_state, sizeof(struct something));
Then alloc_commit_node() can also use the alloc_node() function in its
I checked that the alloc_node() function was actually inlined by gcc,
which it was for -O1 -> -O3 (but not for -O0, obviously). The generated
assembler looked very similar (but not identical) to the code generated
without this patch. Also, I did a quick (and admittedly unsophisticated)
performance test. I could not detect any difference, within the noise
level of the timings, between the two. (Also, operf barely registered
any samples against the alloc functions, for './git log -p >/dev/null').
I also checked the assembler generated by clang, and the story was _almost_
the same. For -O2 -> -O3, clang produced very similar results to gcc.
For -O1, clang didn't inline alloc_node(), but used it as a 'leaf'
function; the blob allocator function 'fell into' alloc_node() and the
other DEFINE-ed allocators 'jmp'-ed to alloc_node() rather than call-ing
it. The alloc_commit_node() allocator did actually call alloc_node().
(probably because it was more complicated than a single return ...).
Note this was tested (on 32-bit Linux Mint 17) with gcc 4.8.2 and
clang 3.4. (Other compilers probably will behave differently ...)
The second patch is just a minor clean-up and could be squashed into
the first patch. (NOTE: I assume that you want c->index to start at
zero; if not ...)
Ramsay Allan Jones (2):
alloc.c: remove the alloc_raw_commit_node() function
alloc.c: remove the redundant commit_count variable
alloc.c | 50 ++++++++++++++++++++++++++++++--------------------
1 file changed, 30 insertions(+), 20 deletions(-)
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