// This is a weird looking number! We really want our first request size to be 1MiB,
// which is a common IO size. But Linux's readahead will try to read an extra 128k on on
// top of a 1MiB read, which we'd have to wait for a second request to service. Because
// FUSE doesn't know the difference between regular reads and readahead reads, it will
// send us a READ request for that 128k, so we'll have to block waiting for it even if
// the application doesn't want it. This is all in the noise for sequential IO, but
// waiting for the readahead hurts random IO. So we add 128k to the first request size
// to avoid the latency hit of the second request.
//
// Note the CRT does not respect this value right now, they always return chunks of part size
// but this is the first window size we prefer.
const INITIAL_READ_WINDOW_SIZE: usize = 1024 * 1024 + 128 * 1024;github.com/awslabs/mountpoint-s3/mountpoint-s3-fs/src/s3/config.rs:243-254