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https://issues.apache.org/jira/browse/DISPATCH-1372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16873676#comment-16873676
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ASF GitHub Bot commented on DISPATCH-1372:
------------------------------------------
codecov-io commented on issue #525: DISPATCH-1372 alloc_pool intrusive linked
list can be replaced by a linked stack
URL: https://github.com/apache/qpid-dispatch/pull/525#issuecomment-504422052
#
[Codecov](https://codecov.io/gh/apache/qpid-dispatch/pull/525?src=pr&el=h1)
Report
> Merging
[#525](https://codecov.io/gh/apache/qpid-dispatch/pull/525?src=pr&el=desc) into
[master](https://codecov.io/gh/apache/qpid-dispatch/commit/5885b4fa29f81cf394521ca6729538fe6273263f?src=pr&el=desc)
will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.
[](https://codecov.io/gh/apache/qpid-dispatch/pull/525?src=pr&el=tree)
```diff
@@ Coverage Diff @@
## master #525 +/- ##
==========================================
+ Coverage 86.86% 86.87% +<.01%
==========================================
Files 87 87
Lines 19519 19554 +35
==========================================
+ Hits 16956 16988 +32
- Misses 2563 2566 +3
```
| [Impacted
Files](https://codecov.io/gh/apache/qpid-dispatch/pull/525?src=pr&el=tree) |
Coverage Δ | |
|---|---|---|
|
[src/alloc\_pool.c](https://codecov.io/gh/apache/qpid-dispatch/pull/525/diff?src=pr&el=tree#diff-c3JjL2FsbG9jX3Bvb2wuYw==)
| `98.55% <100%> (+0.3%)` | :arrow_up: |
|
[src/router\_core/transfer.c](https://codecov.io/gh/apache/qpid-dispatch/pull/525/diff?src=pr&el=tree#diff-c3JjL3JvdXRlcl9jb3JlL3RyYW5zZmVyLmM=)
| `94.6% <0%> (-0.78%)` | :arrow_down: |
|
[src/router\_core/agent\_link.c](https://codecov.io/gh/apache/qpid-dispatch/pull/525/diff?src=pr&el=tree#diff-c3JjL3JvdXRlcl9jb3JlL2FnZW50X2xpbmsuYw==)
| `67.52% <0%> (-0.52%)` | :arrow_down: |
|
[src/parse.c](https://codecov.io/gh/apache/qpid-dispatch/pull/525/diff?src=pr&el=tree#diff-c3JjL3BhcnNlLmM=)
| `84.76% <0%> (-0.24%)` | :arrow_down: |
|
[src/router\_core/router\_core.c](https://codecov.io/gh/apache/qpid-dispatch/pull/525/diff?src=pr&el=tree#diff-c3JjL3JvdXRlcl9jb3JlL3JvdXRlcl9jb3JlLmM=)
| `86.53% <0%> (-0.2%)` | :arrow_down: |
|
[src/iterator.c](https://codecov.io/gh/apache/qpid-dispatch/pull/525/diff?src=pr&el=tree#diff-c3JjL2l0ZXJhdG9yLmM=)
| `89.23% <0%> (+0.19%)` | :arrow_up: |
|
[src/router\_node.c](https://codecov.io/gh/apache/qpid-dispatch/pull/525/diff?src=pr&el=tree#diff-c3JjL3JvdXRlcl9ub2RlLmM=)
| `93.81% <0%> (+0.24%)` | :arrow_up: |
------
[Continue to review full report at
Codecov](https://codecov.io/gh/apache/qpid-dispatch/pull/525?src=pr&el=continue).
> **Legend** - [Click here to learn
more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by
[Codecov](https://codecov.io/gh/apache/qpid-dispatch/pull/525?src=pr&el=footer).
Last update
[5885b4f...a946341](https://codecov.io/gh/apache/qpid-dispatch/pull/525?src=pr&el=lastupdated).
Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
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> alloc_pool intrusive linked list can be replaced by a linked stack
> ------------------------------------------------------------------
>
> Key: DISPATCH-1372
> URL: https://issues.apache.org/jira/browse/DISPATCH-1372
> Project: Qpid Dispatch
> Issue Type: Improvement
> Components: Routing Engine
> Affects Versions: 1.8.0
> Reporter: Francesco Nigro
> Priority: Major
> Attachments: DOOM-3-BFG-Technical-Note.pdf,
> image-2019-06-21-11-08-17-015.png, image-2019-06-21-11-09-02-228.png,
> linked_list_misses.svg, stack_list_misses.svg
>
>
> alloc_pool is currently using a intrusive linked list approach to reduce the
> need of external data structures to hold data, saving expensive pointer
> chasing, but on modern architectures the data dependency between a current
> node and next/prev prevent the CPU prefetcher to stream nodes speculatively.
> There are different approaches that could benefit of prefetcing, but need to
> decouple the data stored from its container eg a linked stack.
> A linked stack is composed by doubly-linked chunks (allocated lazily) that
> make possible for the CPU to prefetch next/prev pointers given that those are
> already contained in the current chunk (if any).
> Although it seems counter-intuitive (given that introduce 1 more hop to reach
> the data), such data-structure is much more cache-friendly on modern
> architectures: I will attach some cache misses analysis to show it.
>
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