# Investigating large latency on a constrained Windows environment

**URL:** <https://discourse.julialang.org/t/investigating-large-latency-on-a-constrained-windows-environment/114482>\
**Category:** General Usage\
**Tags:** startup, ttfp, ttfx, latency\
**Created:** [May 18, 2024, 11:07am UTC](https://discourse.julialang.org/t/investigating-large-latency-on-a-constrained-windows-environment/114482 "2024-05-18T11:07:44Z")\
**Posts on this page:** 1\
**Showing post:** 70

<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [May 21, 2024, 2:18pm UTC](https://discourse.julialang.org/t/investigating-large-latency-on-a-constrained-windows-environment/114482/70 "2024-05-21T14:18:44Z")

</div>

Yes, that matches my expectation. We can isolate the effect to DLL loading.

We can build a simple DLL using zig as follows.

```julia-repl
julia> using zig_jll

julia> write("add.zig",
       """
       export fn add(a: i32, b: i32) i32 {
           return a + b;
       }
       """)
56

julia> zig = zig_jll.zig();

julia> run(`$zig build-lib -dynamic -lc add.zig`);

julia> using Libdl

julia> @time dlopen("./libadd.so") # probably add.dll for you
Ptr{Nothing} @0x0000000000c39e10

julia> libadd = :libadd
:libadd

julia> @ccall libadd.add(5::Int32, 5::Int32)::Int32
10

```

Later I will expand this to build an executable that loads the DLL with timings. Then we’ll know if this is Julia specific or not.

```julia
julia> write("testdll.zig",
       """
       const std = @import("std");
       pub fn main() !void {
           const start = std.time.microTimestamp();
           var lib = try std.DynLib.open("libadd.dll");
           const stop = std.time.microTimestamp();
           const elapsed = stop - start;
           const add = lib.lookup(*fn (i32,i32) i32, "add").?;
           std.debug.print("add {} in {}\\n", .{add(5,6), elapsed});
       }
       """)
332

julia> run(`$zig build-exe testdll.zig`);

julia> run(`.\testdll.exe`)

```

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