use io.CopyBuffer with explicitly allocated buffers #69
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ghost
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io.Copy uses a 32KB buffer, which pprof indicates result in significant memory usage.
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The 4096B buffer LGTM as in practice the max MTU for Ethernet networks is 1500B. I think we disable Nagle (I could be mistaken), so we can do with smaller buffers. But my assumptions could be wrong.
However, I think we would benefit from using a sync.Pool here to further curtail memory thrashing and GC pressure. WDYT?
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Yeah, we could use a sync.Pool, steb made the same comment. Does it ever return memory? I am worried about hoarding memory when we scale up. |
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reading the docs, it explicitly mentioned that pooled objects may be gc'ed which is nice. |
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Yeah, it holds weak references, so unused elements are elegible for collection by the GC :-) |
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Added a pool. |
relay.go
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| @@ -85,6 +87,11 @@ func NewRelay(ctx context.Context, h host.Host, upgrader *tptu.Upgrader, opts .. | |||
| incoming: make(chan *Conn), | |||
| relays: make(map[peer.ID]struct{}), | |||
| liveHops: make(map[peer.ID]map[peer.ID]int), | |||
| bufPool: sync.Pool{ | |||
| New: func() interface{} { | |||
| return make([]byte, 4096) | |||
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So, welcome to go. Converting a []byte to an interface{} allocates. Let's just use https://github.com/libp2p/go-buffer-pool (https://godoc.org/github.com/libp2p/go-buffer-pool#Get)
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Oh wow, that's nuts.
Yeah, I'll use go-buffer-pool.
io.Copyuses a 32KB buffer, which as pprof indicates results in significant memory usage.This changes to using
io.CopyBufferdirectly with 4KB buffers.