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diff --git a/chromium/docs/website/site/chromium-os/chromiumos-design-docs/library-optimization/index.md b/chromium/docs/website/site/chromium-os/chromiumos-design-docs/library-optimization/index.md deleted file mode 100644 index 7675ba95c5a..00000000000 --- a/chromium/docs/website/site/chromium-os/chromiumos-design-docs/library-optimization/index.md +++ /dev/null @@ -1,70 +0,0 @@ ---- -breadcrumbs: -- - /chromium-os - - Chromium OS -- - /chromium-os/chromiumos-design-docs - - Design Documents -page_name: library-optimization -title: Library Optimization ---- - -## Problem - -One of the optimizations proposed for Chrome OS was the shrinking of C libraries -by removing the unused symbols from them. -This document describes the work done in this direction. - -## Existing solution - -Prior work has been done in this field by Montavista, which released an open -source set of scripts called the [Library Optimizer -Tool](http://libraryopt.sourceforge.net/) (libopt). According to their site: - -The Library Optimizer examines the complete target file system, resolves all -shared library symbol references, and rebuilds the shared libraries with only -the object files required to satisfy the symbol references - -Sadly the script is not very well documented (both in the way someone could use -it without modifying it and the way it works internally). After examining the -contents of the script and the example build script for libc it seems that the -script does indeed return a list of .o files which should be included in the -library after analyzing symbol dependencies. It can also receive a strip -parameter which uses the strip command to strip the .notes and the .comments -sections from the library. -I have modified the script to print out a lot of debug information and I have -created my own simple library to test the script on. Sadly the script did not -work as expected, as it didn’t output the expected .o file names. - -## New solution - -Some of the members of the compiler team came up with a new solution, which -would still involve passing a list of symbols to the linker, but which is less -error-prone as the linker can automatically detect the dependencies which these -symbols introduce. -The binaries can apparently be stripped of unused symbols using the garbage -collector, however this is not done by default yet on all Chromium OS packages. -Stripping the libraries is the interesting part, but this cannot be done -automatically without a view of the whole system. The solution presented by the -compiler team involves manipulating the visibility of functions and using -function sections and garbage collection to eliminate the unused symbols from -the library. -The current problems with this approach are: - -1. Using -ffunction-sections is supposed to increase the library size - but is needed for the shrink, must investigate if how much space is - saved -2. dlopen()/dlsym() breaks this method so they will have to be allowed - somehow - -## Current work - -A script has been created which currently: - -1. Builds a list of all the undefined symbols used by executables. -2. See what symbols are not used anywhere and marks them as unused - -The next steps are: - -1. Relink the libraries so that the unused symbols get removed (start - off with a small number of libraries) -2. Make it work with dlopen/dlsym.
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