On 2020/04/28 3:45, Alexey Dobriyan wrote:
>> - if (td->o.zone_mode == ZONE_MODE_ZBD) {
>> - ret = zbd_adjust_block(td, io_u);
>> - if (ret == io_u_eof)
>> - return 1;
>> - }
>> + ret = zbd_adjust_block(td, io_u);
>> + if (ret == io_u_eof)
>> + return 1;
>
> This is cleaner code but probably won't result in performance changes
> because it is trading a branch and a regular function call to a branch
> and indirect function call.
>
Yes. I wondered how to best avoid overhead for the regular case. Tried different
things but this one was the cleanest and probably has the least impact on zbd
mode itself. I am starting to think that it may be better to have a
zbd_fill_io_u() function called in place of the regular fill_io_u(). That would
reduce the 3 conditionals we have for zbd to one only, and also allow more
liberty with io_u adjustments for zbd without impacting the regular device case.
Thoughts ?
--
Damien Le Moal
Western Digital Research
