Re: [gold][patch] Reduce heap usage for string merge sections

[Cary Coutant <ccoutant at google dot com>]

This time with the patch attached.

On Tue, Jul 20, 2010 at 4:09 PM, Cary Coutant <ccoutant@google.com> wrote:
> I used tcmalloc to profile the heap usage of gold while building a
> large binary compiled with -O2 and -g, and found that the
> Merged_strings structures were responsible for just over 50% of the
> total heap used by gold. That structure has 6 fields: a pointer to the
> object, the input section index, the input offset, a pointer to the
> string itself, the length of the string, and the stringpool key. The
> string field was never used, so I removed it. The pointer to the
> object and the input section index were common across fairly large
> lists of strings, so I separated the one list per output section into
> separate lists for each (object, shndx), and removed those two fields
> from the Merged_string struct. The length field was easily recomputed
> by subtracting adjacent input offsets, so I removed it, too. The
> result is a 67% reduction in the size of the Merged_string structure,
> and the net effect was to reduce the total heap used for my benchmark
> from 3.45 GiB to 2.56 GiB (25% less heap).
>
> The Object_merge_map structure is now responsible for more heap than
> anything else; I'll be taking a look at reducing its memory footprint
> next.
>
> Tested on x86_64 Linux. OK?
>
> -cary
>
> ? ? ? ?* merge.h (Output_merge_string::Merged_string): Remove object, shndx,
> ? ? ? ?string, and length fields.
> ? ? ? ?(Output_merge_string::Merged_strings_list): New type.
> ? ? ? ?(Output_merge_string::Merged_strings_lists): New typedef.
> ? ? ? ?(Output_merge_string): Replace merged_strings_ with
> ? ? ? ?merged_strings_lists_.
> ? ? ? ?* merge.cc (Output_merge_string::do_add_input_section): Allocate new
> ? ? ? ?Merged_strings_list per input object and section. ?Don't store pointer
> ? ? ? ?to the string. ?Don't store length with each merged string entry.
> ? ? ? ?(Output_merge_string::finalize_merged_data): Loop over list of merged
> ? ? ? ?strings lists. ?Recompute length of each merged string.
>

Attachment: gold-compress-debug-patch.txt
Description: Text document