feat : Implement slot-based MGET batching for cluster clients #908

SoulPancake · 2025-10-04T08:12:38Z

Implement slot-based MGET batching for cluster clients Co-authored-by: SoulPancake <[email protected]>

jit-ci · 2025-10-04T08:12:53Z

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rueian

Functionally, it works, but can we optimize allocations?

SoulPancake · 2025-10-10T05:04:47Z

I optimised the slice mem allocation, is there any other potential improvement I can work on? @rueian

helper.go

rueian · 2025-10-10T18:05:04Z

I optimised the slice mem allocation, is there any other potential improvement I can work on? @rueian

I wonder if it is possible to avoid using MGets since it allocates a make(map[uint16]Completed, 8) though I am not sure if it is allocated on the heap or the stack after compiler optimization. Would you mind checking that? If it is allocated on the stack, then it should be fine.

SoulPancake · 2025-10-20T07:29:36Z

I wonder if it is possible to avoid using MGets since it allocates a make(map[uint16]Completed, 8) though I am not sure if it is allocated on the heap or the stack after compiler optimization. Would you mind checking that? If it is allocated on the stack, then it should be fine.

@rueian
make(map[uint16]Completed, 8) in MGets/JsonMGets does escape to heap.
What do you suggest we do here

rueian · 2025-10-20T16:20:18Z

What do you suggest we do here

Try inline MGets/JsonMGets manually.
Then replacing make(map[uint16]Completed, 8) with make(map[uint16]int, 8) where the values are the indexes of cmds.s, eliminating the use of slotCmds.

SoulPancake · 2025-10-21T17:50:57Z

I have some trouble will my personal laptop, I will address these in a week approx, hope that is okay

Co-authored-by: Rueian <[email protected]>

SoulPancake · 2025-10-29T10:18:36Z

@rueian
I inlined the grouping logic:

Added CRC16 hashing and slot calculation functions (copied from internal/cmds/slot.go) to helper.go for key-to-slot mapping. Let me know if I should move this to a common util?
Replaced the intl.MGets/intl.JsonMGets calls with manual key grouping into a map[uint16][]string.
Built the command slice (cmds.s) directly using the client builder (client.B().Mget().Key(group...).Build().Pin() for MGet, and similarly for JsonMGet with path).
Maintained a parallel cmdKeys slice to track keys per command for response parsing.
Eliminated the intermediate slotCmds map of Completed structs, reducing heap pressure while preserving functionality.

helper.go

SoulPancake · 2025-11-05T13:48:10Z

Hi @rueian Any chance to review this?

helper.go

jit-ci

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rueian · 2025-11-27T02:32:44Z

helper.go

+	slotCount := make(map[uint16]int, len(keys)/2)
+	for _, key := range keys {
+		slotCount[slot(key)]++
+	}
+	cmds := mgetcmdsp.Get(0, len(slotCount))
+	defer mgetcmdsp.Put(cmds)
+	for s := range slotCount {
+		var builder any = client.B().Mget()
+		var first = true
+		for _, key := range keys {
+			if slot(key) == s {
+				if first {
+					builder = builder.(intl.Mget).Key(key)
+					first = false
+				} else {
+					builder = builder.(intl.MgetKey).Key(key)
+				}
+			}
+		}
+		cmds.s = append(cmds.s, builder.(intl.MgetKey).Build().Pin())


Hi @SoulPancake,

Right now, you count the number of keys for each slot, but then discard them, and then iterate over the whole keys slice for each slot, which I think is super inefficient.

How about storing the resulting indexes of cmd.s to the map[uint16]int map first? As I said previously. So that you can use slot(key) to locate the index of cmds.s and only iterate the keys slice twice in total.

rueian · 2025-11-29T21:11:10Z

helper.go

+	}
+
+	slotIdx := make(map[uint16]int, len(keys)/2)
+	var builders []any


Suggested change

var builders []any

cmds := mgetcmdsp.Get(0, len(keys))

defer mgetcmdsp.Put(cmds)

Again, we should avoid additional allocations. This builders []any can be replaced by the cmds.s

Initial plan

e226605

Implement slot-based MGET batching for cluster clients Co-authored-by: SoulPancake <[email protected]>

rueian reviewed Oct 5, 2025

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feat: optimise slices

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SoulPancake and others added 3 commits October 29, 2025 15:04

Apply suggestion from @rueian

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Co-authored-by: Rueian <[email protected]>

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Co-authored-by: Rueian <[email protected]>

feat: address comments

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SoulPancake force-pushed the ab/improve-MGET-helper-cluster branch from 32627b2 to 39a9e9f Compare October 29, 2025 10:17

Merge branch 'redis:main' into ab/improve-MGET-helper-cluster

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feat: remove Slot public func

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SoulPancake requested a review from rueian October 30, 2025 16:59

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SoulPancake added 2 commits November 15, 2025 13:02

Merge branch 'redis:main' into ab/improve-MGET-helper-cluster

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feat: eliminate temp slice alloc

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fix: reduce allocations

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feat: address comments

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SoulPancake requested a review from rueian November 29, 2025 11:19

rueian reviewed Nov 29, 2025

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Merge branch 'redis:main' into ab/improve-MGET-helper-cluster

58b3a03

	var builders []any
	cmds := mgetcmdsp.Get(0, len(keys))
	defer mgetcmdsp.Put(cmds)

feat : Implement slot-based MGET batching for cluster clients #908

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