Further optimize off-heap traversal during minor GC #5195
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PB_ACTIVE_WRITER was set without PB_IS_WRITABLE
Only traverse first part of off-heap list that reside on the new-heap, except for writable binaries that are now kept in a separate list. Earlier during minor GC, traversing the off-heap list was continued to the end over terms residing on the old-heap. This for two reasons: 1. The BIN_OLD_VHEAP value was calculated by adding the sizes of all ProcBin's on the old-heap. 2. All writable binaries are handled by shrinking (reallocating) binaries that have not been written to since last GC. Even binaries residing on the old-heap. To optimize and only traverse the first part the off-heap list that reside on the new-heap, we now 1. maintain a correct value of BIN_OLD_VHEAP so it does not have to be recalculated during GC. 2. keep all writable binaries in a separate list Process.wrt_bins that is traversed to the end during every GC. The aim of this commit has been to maintain the overall GC semantics and especially not alter the value of BIN_OLD_VHEAP or how binaries have been reallocated at the end of a GC.
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When creating a new proc bin because tracing has removed the writable flag from the proc bin, we must make sure to also create a new sub binary if the sub binary is on the mature or old heap. When this is not done, the subbinary can be promoted to the old heap without the proc bin also being there. Bug was introduced in erlang#5195, aka e16e545
garazdawi
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When creating a new proc bin because tracing has removed the writable flag from the proc bin, we must make sure to also create a new sub binary if the sub binary is on the mature or old heap. When this is not done, the subbinary can be promoted to the old heap without the proc bin also being there. Bug was introduced in erlang#5195, aka e16e545
garazdawi
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When creating a new proc bin because tracing has removed the writable flag from the proc bin, we must make sure to also create a new sub binary if the sub binary is on the mature or old heap. When this is not done, the subbinary can be promoted to the old heap without the proc bin also being there. Bug was introduced in erlang#5195, aka e16e545
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When writable binaries were introduced in erlang#5195, they weren't added to the output of `process_info(Pid, binary)`. It led to interesting effects of binaries suddenly disappearing after running implicit GC caused by BIF calls, including `process_info` itself. Effectively, running `process_info(self(), binary)` twice in a row resulted in different lists, because first call triggers GC clearing out original binary from the off-heap list: start() -> OffHeapBin = crypto:strong_rand_bytes(1024 * 1024), Bin = <<OffHeapBin/binary, "a">>, Before = erlang:process_info(self(), [binary]), After = erlang:process_info(self(), [binary]), Before =/= After andalso erlang:display({wtf, Before, After}), Bin. Fixes erlang#6573
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Only traverse first part of off-heap list that reside on the new-heap, except for writable binaries that are now kept in a separate list.
Fixes #4424.
Earlier during minor GC, traversing the off-heap list was continued to the end over terms residing on the old-heap. This for two reasons:
ProcBin's on the old-heap.To optimize and only traverse the first part the off-heap list that reside on the new-heap, we now
Process.wrt_binsthat is traversed to the end during every GC.The aim of this PR has been to maintain the overall GC semantics and especially not alter the value of BIN_OLD_VHEAP or how binaries have been reallocated at the end of a GC.