# Tracking occupied memory

**URL:** https://discourse.julialang.org/t/tracking-occupied-memory/102442
**Category:** New to Julia
**Created:** [August 3, 2023, 11:30am UTC](https://discourse.julialang.org/t/tracking-occupied-memory/102442 "2023-08-03T11:30:07Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Jad\_Zeitouni](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jad_zeitouni/32/50678_2.png) [@Jad\_Zeitouni](https://discourse.julialang.org/u/Jad_Zeitouni)
#### Post date: [August 3, 2023, 11:30am UTC](https://discourse.julialang.org/t/tracking-occupied-memory/102442/1 "2023-08-03T11:30:07Z")

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Is there any way to track occupied memory in Julia? Unfortunately I can’t provide a MWE but the code does something like this:

```julia
struct State
    params::@NamedTuple begin
       ... # Bunch of vectors and matrices of Float64
    end
    aux::@NamedTuple begin
        ... # Different set of vectors and matrices
    end
end

mutable struct Chain{T<:NamedTuple, S<:State}
    state::S
    past_states::Vector{T}
end

function f!(chain::Chain)
    state = update(chain.state)
    push!(chain.past_states, state.parameters)
    chain.state = state
end

state = ... # some randomly initialized state
chain = Chain(state, [state.parameters])

for _ in 1:10000
    f!(chain)
end

```

So now when i run `varinfo()`, I correctly see that `chain` has about 8GB in memory. But then I run

```julia
chain = nothing
GC.gc()

```

and the memory remains occupied. I tried coming up with a simpler example but the memory cleared. My guess is that something is happening in `update` that causes some of the internals of `chain` to remain referenced even after I reassign `chain` to `nothing`.

Is there anyway to check what’s holding that memory? Note that `update` does use threading, but this happens even if the number of threads is one.