2022-10-11 22:25:54 +00:00
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[package]
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name = "rope"
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version = "0.1.0"
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edition = "2021"
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2023-01-18 20:28:02 +00:00
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publish = false
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2024-01-27 12:51:16 +00:00
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license = "GPL-3.0-or-later"
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2024-01-23 16:40:30 +00:00
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2024-03-05 17:01:17 +00:00
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[lints]
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workspace = true
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2022-10-11 22:25:54 +00:00
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[lib]
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path = "src/rope.rs"
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[dependencies]
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2024-01-31 02:41:29 +00:00
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arrayvec = "0.7.1"
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2024-03-21 20:10:18 +00:00
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bromberg_sl2 = { git = "https://github.com/zed-industries/bromberg_sl2", rev = "950bc5482c216c395049ae33ae4501e08975f17f" }
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2024-01-31 02:41:29 +00:00
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log.workspace = true
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2023-04-25 00:41:55 +00:00
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smallvec.workspace = true
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2024-02-06 19:41:36 +00:00
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sum_tree.workspace = true
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util.workspace = true
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2022-10-11 22:25:54 +00:00
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[dev-dependencies]
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2024-02-06 19:41:36 +00:00
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gpui = { workspace = true, features = ["test-support"] }
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2023-04-25 00:41:55 +00:00
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rand.workspace = true
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2024-02-06 19:41:36 +00:00
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util = { workspace = true, features = ["test-support"] }
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Reduce memory usage to represent buffers by up to 50% (#10321)
This should help with some of the memory problems reported in
https://github.com/zed-industries/zed/issues/8436, especially the ones
related to large files (see:
https://github.com/zed-industries/zed/issues/8436#issuecomment2037442695),
by **reducing the memory required to represent a buffer in Zed by
~50%.**
### How?
Zed's memory consumption is dominated by the in-memory representation of
buffer contents.
On the lowest level, the buffer is represented as a
[Rope](https://en.wikipedia.org/wiki/Rope_(data_structure)) and that's
where the most memory is used. The layers above — buffer, syntax map,
fold map, display map, ... — basically use "no memory" compared to the
Rope.
Zed's `Rope` data structure is itself implemented as [a `SumTree` of
`Chunks`](https://github.com/zed-industries/zed/blob/8205c52d2bc204b8234f9306562d9000b1691857/crates/rope/src/rope.rs#L35-L38).
An important constant at play here is `CHUNK_BASE`:
`CHUNK_BASE` is the maximum length of a single text `Chunk` in the
`SumTree` underlying the `Rope`. In other words: It determines into how
many pieces a given buffer is split up.
By changing `CHUNK_BASE` we can adjust the level of granularity
withwhich we index a given piece of text. Theoretical maximum is the
length of the text, theoretical minimum is 1. Sweet spot is somewhere
inbetween, where memory use and performance of write & read access are
optimal.
We started with `16` as the `CHUNK_BASE`, but that wasn't the result of
extensive benchmarks, more the first reasonable number that came to
mind.
### What
This changes `CHUNK_BASE` from `16` to `64`. That reduces the memory
usage, trading it in for slight reduction in performance in certain
benchmarks.
### Benchmarks
I added a benchmark suite for `Rope` to determine whether we'd regress
in performance as `CHUNK_BASE` goes up. I went from `16` to `32` and
then to `64`. While `32` increased performance and reduced memory usage,
`64` had one slight drop in performance, increases in other benchmarks
and substantial memory savings.
| `CHUNK_BASE` from `16` to `32` | `CHUNK_BASE` from `16` to `64` |
|-------------------|--------------------|
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### Real World Results
We tested this by loading a 138 MB `*.tex` file (parsed as plain text)
into Zed and measuring in `Instruments.app` the allocation.
#### standard allocator
Before, with `CHUNK_BASE: 16`, the memory usage was ~827MB after loading
the buffer.
| `CHUNK_BASE: 16` |
|---------------------|
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After, with `CHUNK_BASE: 64`, the memory usage was ~396MB after loading
the buffer.
| `CHUNK_BASE: 64` |
|---------------------|
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#### `mimalloc`
`MiMalloc` by default and that seems to be pretty aggressive when it
comes to growing memory. Whereas the std allocator would go up to
~800mb, MiMalloc would jump straight to 1024MB.
I also can't get `MiMalloc` to work properly with `Instruments.app` (it
always shows 15MB of memory usage) so I had to use these `Activity
Monitor` screenshots:
| `CHUNK_BASE: 16` |
|---------------------|
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| `CHUNK_BASE: 64` |
|---------------------|
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### Release Notes
Release Notes:
- Reduced memory usage for files by up to 50%.
---------
Co-authored-by: Antonio <antonio@zed.dev>
2024-04-09 16:07:53 +00:00
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criterion = { version = "0.4", features = ["html_reports"] }
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[[bench]]
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name = "rope_benchmark"
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harness = false
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