Optimise memory deallocation for stable log entries #96
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… underlying-array utilisation Signed-off-by: Aditya-Sood <[email protected]>
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hi @pavelkalinnikov, could you please review the PR? |
Signed-off-by: Aditya-Sood <[email protected]>
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hi @pavelkalinnikov, does the PR need any changes? |
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hi @pavelkalinnikov, could you please review the PR? |
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@Aditya-Sood Sorry, been super busy recently. Will review this PR this week. |
| const lenMultiple = 2 | ||
| if len(u.entries) == 0 { | ||
| func (u *unstable) shrinkEntriesSlice(nextUnstableEntryIndex int) { | ||
| if nextUnstableEntryIndex == len(u.entries) { //all log entries have been successfully stored |
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nit: Please add a whitespace between // and the comment. Same bellow.
| countStableEntries := nextUnstableEntryIndex | ||
| if countStableEntries > cap(u.entries)/lenMultiple { | ||
| return true | ||
| } |
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This heuristic is different from the proposed idea in #71. It still honours only "visible" entries in deciding when to compact; and so it is susceptible to the same problem. The idea that was proposed is that we should instead track the full allocated size of the underlying slice.
This heuristic also seems different from the original: it checks the ratio of stable entries vs. cap; previously it checked the ratio of all entries vs. cap. Any particular reason why you went with this heuristic?
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hi @pavelkalinnikov, thanks for the review
I forgot that cap() considers the backing array only for the last index, not the beginning one
I had another thought - at the time of shrinking the entries slice, if we remove references to the shrunk pb.Entry elements, then two things will happen:
- with no more references, the 'shrunk'
pb.Entryvalues will immediately become available for GC (if not in use) - the
append()method will consider creating an entirely new backing array at the time of adding new elements when capacity is low, and then the preceding unreachable values (which currently hold emptypb.Entryvalues after the above change) will also become available for GC
this seemed like a much cleaner solution to me
if this approach seems feasible, then we can optimise the design further by replacing pb.Entry values with pointers instead, to further minimise the memory cost of holding shrunk values in the array until append() replaces the backing array
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hi @pavelkalinnikov, could you please share your review of the above approach?
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hi @pavelkalinnikov, could you please share your thoughts on this approach - #96 (comment) |
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hi @ahrtr, would you be able to weigh-in on #96 (comment)? |
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hi @mitake, @serathius, @ptabor, @spzala |
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hi @pav-kv |
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QQ for any optimisation, do we have a benchmark that confirms the improvement? |
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hi @serathius, no I haven't implemented the proposed change yet |
Increment: Modify unstable.shrinkEntriesArray() to better account for underlying-array utilisation
Fixes #71