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int_ua
Asked: 2017-12-14 13:08:03 +0800 CST

Why is chromium-browser 63 so much bigger than 62?

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I've noticed that apt estimates the upgrade to take 48.1MB more space on upgrading from 62.0.3202.94-0ubuntu0.16.04.1317 to 63.0.3239.84-0ubuntu0.16.04.1. I've skimmed through apt changelog chromium-browser and don't see anything that's described as taking much more space. Is there a quick way to see what files changed with apt or anyone who knows or will find the reason?

$ apt list --upgradable
chromium-browser/xenial-updates,xenial-security 63.0.3239.84-0ubuntu0.16.04.1 amd64 [upgradable from: 62.0.3202.94-0ubuntu0.16.04.1317]
chromium-codecs-ffmpeg-extra/xenial-updates,xenial-security 63.0.3239.84-0ubuntu0.16.04.1 amd64 [upgradable from: 62.0.3202.94-0ubuntu0.16.04.1317]
$ sudo apt dist-upgrade
The following packages will be upgraded:
chromium-browser chromium-codecs-ffmpeg-extra
2 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 74.4 MB of archives.
After this operation, 48.1 MB of additional disk space will be used.
package-management

1 Answers

  1. Best Answer

    The size difference seems to be from a new v8_context_snapshot_generator binary file. I extracted the contents of the debs and compared them:

    $ ls -sSh 6*/usr/lib/chromium-browser
61/usr/lib/chromium-browser:
total 222M
132M chromium-browser      5.0M libGLESv2.so                1.5M libVkLayer_unique_objects.so        1.1M chrome_200_percent.pak    220K natives_blob.bin       4.0K WidevineCdm            4.0K v8_build_config.json
 14M resources.pak     3.0M gn                  1.5M libVkLayer_swapchain.so         784K libVkLayer_threading.so   152K mus_app_resources_200.pak  4.0K angledata             0 libs
 13M ui.service        2.9M test_ime_driver.service         1.4M keyboard_resources.pak          772K chrome_100_percent.pak    128K views_mus_resources.pak    4.0K locales
9.8M icudtl.dat        2.6M libVkLayer_core_validation.so       1.2M brotli                  576K libwidevinecdmadapter.so   92K mus_app_resources_100.pak  4.0K plugins
9.0M headless_lib.pak      1.9M libVkLayer_parameter_validation.so  1.2M flatc                   508K libEGL.so          40K xdg-mime           4.0K swiftshader
6.7M font_service.service  1.6M libVkLayer_object_tracker.so        1.2M proto_zero_plugin           508K libwidevinecdm.so      36K xdg-settings           4.0K mus_app_resources_strings.pak
6.6M toolchain.ninja       1.5M snapshot_blob.bin           1.1M transport_security_state_generator  472K character_data_generator   16K chrome-sandbox         4.0K args.gn

63/usr/lib/chromium-browser:
total 270M
134M chromium-browser           3.0M test_ime_driver.service         1.2M snapshot_blob.bin           504K libEGL.so               44K chrome_100_percent.pak.info         4.0K WidevineCdm
 44M v8_context_snapshot_generator  2.7M libVkLayer_core_validation.so       1.2M brotli                  492K libwidevinecdm.so           44K chrome_200_percent.pak.info         4.0K angledata
 14M resources.pak          2.6M gn                  1.2M proto_zero_plugin           472K character_data_generator    40K xdg-mime                4.0K locales
 13M ui.service             1.9M libVkLayer_parameter_validation.so  1.2M flatc                   212K natives_blob.bin        36K views_mus_resources.pak.info        4.0K plugins
9.8M icudtl.dat             1.6M v8_context_snapshot.bin         1.1M transport_security_state_generator  188K headless_lib.pak.info       36K xdg-settings                4.0K swiftshader
9.1M headless_lib.pak           1.6M libVkLayer_object_tracker.so        1.1M chrome_200_percent.pak          156K resources.pak.info          16K chrome-sandbox              4.0K mus_app_resources_strings.pak
7.3M toolchain.ninja            1.5M libVkLayer_unique_objects.so        792K chrome_100_percent.pak          128K mus_app_resources_200.pak   12K mus_app_resources_strings.pak.info  4.0K args.gn
6.5M font_service.service       1.5M libVkLayer_swapchain.so         776K libVkLayer_threading.so         112K views_mus_resources.pak     12K mus_app_resources_100.pak.info      4.0K v8_build_config.json
5.3M libGLESv2.so           1.4M keyboard_resources.pak          576K libwidevinecdmadapter.so         72K mus_app_resources_100.pak   12K mus_app_resources_200.pak.info         0 libs

$ file 63/usr/lib/chromium-browser/v8_*
63/usr/lib/chromium-browser/v8_build_config.json:          ASCII text, with no line terminators
63/usr/lib/chromium-browser/v8_context_snapshot.bin:       data
63/usr/lib/chromium-browser/v8_context_snapshot_generator: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=99a63c90180ec5a32ea8861d44f405942ccbbdab, stripped

    This seems to be a new tool meant to speed creation of V8 contexts. V8 is the JavaScript engine used by Chromium, and creating new V8 contexts is a significant part of the time taken for loading a webpage. The design document suggests that creating contexts from V8 context snapshots should lead to a speedup of up to 3x, and this is meant to be a helper program for creating snapshots in the first place.

    However, reading the design doc suggests including the tool in the package might be an accident, and hence a packaging bug:

    How to create a snapshot?

    A snapshot is created in build time. It means a snapshot is user independent.
    We make an executable file which is run on host side platform to make a snapshot. It simulates the behavior of LocalWindowProxy::Initialize() to create a v8::Context, and outputs a blob file as a result.

    And:

    Concerns

    • This feature increases 1.6MB APK size on Android. It may be large enough to cancel the win.
      • Android has no extensions
      • This feature can increase disk I/O and memory usages.

    The implication is that v8_context_snapshot_generator is to be run during package build time, and not on individual user systems. And the relative small size predicted increase for Android suggests that it doesn't include a 44 MB tool.

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