Nowadays,the IO schedulers in linux kernel have four types:
deadline,noop,Anticiptory and CFQ.CFQ is the default scheduler.But CFQ
is not a good scheduler for SSD,dealine may be a good choice.
When deadline runs,it has a mount of computation about merging and
sorting.Merge has three types: front_merge,no_merge and back_merge.
Why don't have another type: merge based same sector.For example,it
have two bios in a request list,theyboth have the same bi->sector,the
bi->size maybe not equal. Whether can we put the latter bio replace
the former?What do you find that significant?Or the other levels in OS
has finished this
function?