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Some more details about tables

I have a cold, it’s four days I’m laying in bed because of it, and I’m bored. Anyway I sent a few more patches to ffmpeg-devel today, although the fever did increase my mistake ratio.

Anyway, continuing to talk about tables, I’ve also mailed to ffmpeg-devel a simple command to check the amount of .bss tables that are present in libavcodec:

{objdump -t libavcodec/*.o | fgrep .bss | 
awk '{ print $5 }' | sed -e 's:^:0x:' 
-e 's:$: + :'; echo 0; } | irb

The result was surprisingly: 961KiB (plus the tables that I hardcoded locally and sent upstream). This means that every process using libavcodec will use up to that amount of memory of COW’d tables. A fully initialised libavcodec will use that amount of memory in COW’d tables.

Replacing all the tables with hardcoded tables will increase the size of libavcodec library by that size, but in turn, there will be no COW. This means faster startup for the library, as no COW is triggered for initialisation, and less memory used.

Tomorrow, if I feel better, I’ll be adding code for generating the tables to FFmpeg so that it would be less annoying to maintain the tables. I sincerely hope it can be integrated, so that Amarok will use less memory 😉

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