SHM: optimize metadata #1714
SHM: optimize metadata #1714
Conversation
… into sigle "Metadata" structure
yellowhatter
added
enhancement
- change three_node_combination_multicast ports
…ead and less structure sizes for SHM
|
Put ProtocolID and ChunkDescriptor into SHM metadata: less wire overhead and less internal structure sizes for SHM Gains 2% more performance for SHM, but this is not the only thing: it opens a way to implement publish-before-allocated-and-written concept, that should dramatically increase SHM performance and improve latency! |
| @@ -0,0 +1,58 @@ | |||
| // | |||
| // Copyright (c) 2023 ZettaScale Technology | |||
There was a problem hiding this comment.
Make sure it's 2025 for newly-created files.
| #[stabby::stabby] | ||
| pub struct Metadata<const S: usize> { | ||
| headers: [ChunkHeaderType; S], | ||
| watchdogs: [AtomicU64; S], // todo: replace with (S + 63) / 64 when Rust supports it |
There was a problem hiding this comment.
I'm curious to know more about the todo comment here. What's the intended behaviour and current limitations?
There was a problem hiding this comment.
Watchdogs are packed as bits of u64. This means that for S headers we need S/64-sized u64 array. However, stable Rust doesn't support const arithmetic for const generic parameter like this:
watchdogs: [AtomicU64; (S + 63) / 64]
| ) | ||
| } | ||
|
|
||
| pub fn count(&self) -> usize { |
There was a problem hiding this comment.
If count is const, couldn't be an associated const instead of a function?
There was a problem hiding this comment.
Changed in a bit different way: pub const fn
The reason is that associated constant cannot be called through object instance, only as Type::constant, so I need to carry full object type (and it is compilcated) everywhere
const fn is intended to work in the way we need
|
LGTM. I'll just wait to merge it because of the |
Sure, that's intended as I didn't put "release" label :) |
|
@yellowhatter It's well understood that SHM is still marked as unstable, meaning that breaking changes may be introduced. |
@Mallets The idea is clear. I think we can add smth similar to |
I think it makes sense. This would allow us to better control the introduction of additional changes in the future. |
closes #1703
Combined SHM metadata in single storage that is now identified with single descriptor.
By-the-way fixed undiscovered edge case bug with buffer validity check in the receiver code.
Improves SHM performance by 35% (1.7M -> 2.3M) that moves SHM efficiency threshold to somewhat less than 512 bytes.
Breaks backward compatibility for SHM communication. Non-SHM is not affected.