Re: [PATCH v3 04/10] block: introduce dma map backed bio type

[Pavel Begunkov <asml.silence@gmail.com>]

On 5/18/26 13:57, Christoph Hellwig wrote:
> On Mon, May 18, 2026 at 01:40:18PM +0100, Pavel Begunkov wrote:
>>> When that is really a performance critical path then you can use the likely() and unlikely() macros to give the compiler the hint which one to prefer.
>>
>> That might be more penalising than placing them in the right order,
>> and it might be fine as it's new and all that, but it's not a clear
>> cut as it's definitely not created to be a slow path.
> 
> Yes.  Whatever the caller is using at a given time is the fast path here,
> and dynamic branch prediction in modern cpus handles this really well.
> 
>> TBH, not sure
>> why we're bike shedding such things, is it somewhere in the code
>> style?
> 
> It makes reading the code annoying, so it better have a good reason.
> Now for a single conditional it's not much of an issue, but these
> things tend to pile up and then start to get really annoying.
> Always write your code the most straight forward way unless you
> have a good reason not to.

For me, having the most common case first is more natural and
readable, but I'm going to flip it just to avoid spending more
time here.

-- 
Pavel Begunkov