HTTP: Increase max read buffer size to 128KB

[hofst]

Increase the max read buffer size in read_size from 64KB to 128KB. This change aligns with another optimizations in Asio/SSL to reduce io_context contention and CPU utilization by allowing larger reads per operation: chriskohlhoff/asio#1712

[hofst]

@vinniefalco Opened the PR as discussed in the issue here: #3062

[ashtum]

@hofst, it looks like Chris has responded to your issue with this commit: chriskohlhoff/asio@873cb09.

For the Beast part, you can overload beast::read_size_helper for beast's buffer types, or introduce a custom buffer type and http::read_some and http::read will pick up that overload, for example:

struct tuned_buffer : beast::flat_buffer
{
    using beast::flat_buffer::flat_buffer;
};

std::size_t
read_size_helper(tuned_buffer& b, std::size_t)
{
    std::size_t const remaining = b.max_size() - b.size();
    return (std::min)(std::size_t{131072}, remaining);
}

Here is a complete example: https://godbolt.org/z/xTM7sY5MK.

[hofst]

@ashtum That's great, thank you! Now the main part that is missing is the multi-TLS decode per task. The encode-side (upload path) has the same problem by the way and needs a multi-encode implementation to utilize large machines efficiently and fully.