• Anton Bikineev's avatar
    cppgc: Avoid fragmentation in NormalPageMemoryRegion · 1d3a1c6f
    Anton Bikineev authored
    NormalPageMemoryRegion is a span of 10 pages, all of which must belong
    to the same space. This requirement imposes a fragmentation issue for virtual space, which is not ideal for the current 2GB cage
    configuration.
    
    The CL fixes this by mixing pages of different spaces inside the same
    NormalPageMemoryRegion. With cage it's actually not necessary anymore
    to have NormalPageMemoryRegion, but we keep it to allow the code to be
    uniform for cage/non-cage configurations.
    
    There is no type confusion across spaces, since pages (even empty) are
    never shared between spaces. In addition, the shared cage puts an
    additional memory constraint on the GC. So, there is no security benefit
    in having NormalPageMemoryRegion assigned to a single space.
    
    Savings in reserved address space:
    cnn:2021: 14%
    facebook_infinite_scroll:2018: 23%
    
    Bug: chromium:1325007, chromium:1352649
    Change-Id: I7b49032d581dd56feb8633734a1f37803e9526c6
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3840749Reviewed-by: 's avatarMichael Lippautz <mlippautz@chromium.org>
    Commit-Queue: Anton Bikineev <bikineev@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#82584}
    1d3a1c6f
page-memory.h 8.95 KB