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I am not aware of anything that depends on StartupCache being a zip file, and since I want to use lz4 compression because inflate is showing up quite a lot in profiles, it's simplest to just use a custom format. This loosely mimicks the ScriptPreloader code, with a few diversions: - Obviously the contents of the cache are compressed. I used lz4 for this as I hit the same file size as deflate at a compression level of 1, which is what the StartupCache was using previously, while decompressing an order of magnitude faster. Seemed like the most conservative change to make. I think it's worth investigating what the impact of slower algs with higher ratios would be, but for right now I settled on this. We'd probably want to look at zstd next. - I use streaming compression for this via lz4frame. This is not strictly necessary, but has the benefit of not requiring as much memory for large buffers, as well as giving us a built-in checksum, rather than relying on the much slower CRC that we were doing with the zip-based approach. - I coded the serialization of the headers inline, since I had to jump back to add the offset and compressed size, which would make the nice Code(...) method for the ScriptPreloader stuff rather more complex. Open to cleaner solutions, but moving it out just felt like extra hoops for the reader to jump through to understand without the benefit of being more concise. Differential Revision: https://phabricator.services.mozilla.com/D34652 --HG-- extra : moz-landing-system : lando |
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| test | ||
| moz.build | ||
| StartupCache.cpp | ||
| StartupCache.h | ||
| StartupCacheUtils.cpp | ||
| StartupCacheUtils.h | ||