On 24/02/2020 18:53, Jens Axboe wrote: > On 2/24/20 8:50 AM, Pavel Begunkov wrote: >> On 24/02/2020 18:46, Jens Axboe wrote: >>> On 2/24/20 8:44 AM, Pavel Begunkov wrote: >>>>> Fine like this, though easier if you inline the patches so it's easier >>>>> to comment on them. >>>>> >>>>> Agree that the first patch looks fine, though I don't quite see why >>>>> you want to pass in opcode as a separate argument as it's always >>>>> req->opcode. Seeing it separate makes me a bit nervous, thinking that >>>>> someone is reading it again from the sqe, or maybe not passing in >>>>> the right opcode for the given request. So that seems fragile and it >>>>> should go away. >>>> >>>> I suppose it's to hint a compiler, that opcode haven't been changed >>>> inside the first switch. And any compiler I used breaks analysis there >>>> pretty easy. Optimising C is such a pain... >>> >>> But if the choice is between confusion/fragility/performance vs obvious >>> and safe, then I'll go with the latter every time. We should definitely >>> not pass in req and opcode separately. >> >> Yep, and even better to go with the latter, and somehow hint, that it won't >> change. Though, never found a way to do that. Have any tricks in a sleeve? > > We could make it const and just make the assignment a bit hackier... Apart > from that, don't have any tricks up my sleeve. Usually doesn't work because of such possible "hackier assignments". Ok, I have to go and experiment a bit. Anyway, it probably generates a lot of useless stuff, e.g. for req->ctx -- Pavel Begunkov
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