While vectors don’t support std::io::Read, slices do. There is some confusion here caused by Rust being able to coerce a Vec into a slice in some situations but not others. In this case, an explicit coercion to a slice is needed because at the stage coercions are applied, the compiler doesn’t know that Vec<u8> doesn’t … Read more
O_DIRECT alone only promises that the kernel will avoid copying data from user space to kernel space, and will instead write it directly via DMA (Direct memory access; if possible). Data does not go into caches. There is no strict guarantee that the function will return only after all data has been transferred. O_SYNC guarantees … Read more
It would help to understand the role of 3 important aspects of I/O in computer architecture: Interrupts, DMA, and Hardware Controllers. When the CPU issues an I/O request to the hard disk, the hard disk has its own specialized chip called a device (or hardware) controller designed solely for processing commands from the CPU, such … Read more
If your function accepts an io.Writer, you can pass a *bytes.Buffer to capture the output. // import “bytes” buf := new(bytes.Buffer) f(buf) buf.String() // returns a string of what was written to it If it requires an http.ResponseWriter, you can use a *httptest.ResponseRecorder. A response recorder holds all information that can be sent to a … Read more
I know it’s the time spent by the CPU waiting for a IO operations to complete, but what kind of IO operations precisely? What I am also not sure, is why it so important? Can’t the CPU just do something else while the IO operation completes, and then get back to processing data? Yes, the … Read more