* Re: [PATCH 4/7] objtool: reduce memory usage of struct reloc
[not found] ` <20221216-objtool-memory-v1-4-6f2dd3ed7312@weissschuh.net>
@ 2022-12-19 10:52 ` Peter Zijlstra
0 siblings, 0 replies; only message in thread
From: Peter Zijlstra @ 2022-12-19 10:52 UTC (permalink / raw)
To: Thomas Weißschuh; +Cc: Josh Poimboeuf, linux-kernel
On Sun, Dec 18, 2022 at 09:30:07PM +0000, Thomas Weißschuh wrote:
> Use a smaller type for the relocation type and move it to a location in
> the structure where it avoids wasted padding bytes.
>
> Technically ELF could use up to four bytes for the type.
> But until now only types up to number 43 have been defined.
>
> Reduce the size of struct reloc on x86_64 from 120 to 112 bytes.
> This structure is allocated a lot and never freed.
Please put in a assertion for this -- I can see this going sideways fast
if we ever get this wrong.
static inline void reloc_set_type(struct reloc *reloc, int type)
{
if (type > (1U << (8*sizeof(reloc->type))))
WARN_ELF("reloc->type out of range");
reloc->type = type;
}
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2022-12-19 10:52 ` [PATCH 4/7] objtool: reduce memory usage of struct reloc Peter Zijlstra
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