• Dominik Inführ's avatar
    Reland^2: [heap] Store size with invalidated object · 2b79eefe
    Dominik Inführ authored
    This is a reland of commit 23b2d571
    
    When updating pointers during a full GC, a page might not be swept
    already. In such cases there might be invalid objects and slots
    recorded in free memory. Updating tagged slots in free memory is fine
    even though not strictly necessary.
    
    However, the GC also needs to calculate the size of potentially dead
    invalid objects in order to be able to check whether a slot is within
    that object. But since that object is dead, its map might be dead as
    well which makes size calculation impossible on such objects. The CL
    changes this to cache the size of invalid objects. A follow-up CL will
    also check the marking bit of invalid objects.
    
    Reason for reverts:
    
    Revert #2: In-object slack tracking on JSObjects doesn't update the
    cached size of invalidated objects. The fix here was to stop
    invalidating recorded slots on JSObjects at all and avoid that problem
    completely (see https://crrev.com/c/3620274).
    
    Revert #1: Not all size changes go through NotifyObjectLayoutChange, so
    https://crrev.com/c/3607992 introduced NotifyObjectSizeChange as a
    bottleneck for object size changes/right-trimming. This method is
    now used to update the size of invalidated objects.
    
    Bug: v8:12578, chromium:1316289
    Change-Id: I0478d04601c0270ddb39419ca6cf98719951eb4d
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3623542Reviewed-by: 's avatarJakob Linke <jgruber@chromium.org>
    Reviewed-by: 's avatarPatrick Thier <pthier@chromium.org>
    Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
    Reviewed-by: 's avatarMichael Lippautz <mlippautz@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#80344}
    2b79eefe
string.cc 72.7 KB