Re: [Qemu-devel] [Qemu-block] [PATCH v6] migration/block: use blk_pwrite_zeroes for each zero cluster

[Fam Zheng]

On Fri, 04/14 14:48, 858585 jemmy wrote:
> >> Effectively, if no cluster is zero, this patch still splits a big write 
> >> into
> >> small ones, which is the opposition of usual performance optimizations 
> >> (i.e.
> >> trying to coalesce requests).
> >
> > Good point!
> >
> > Another patch can modify the loop to perform the largest writes
> > possible.  In other words, do not perform the write immediately and
> > keep a cluster counter instead.  When the zero/non-zero state changes,
> > perform the write for the accumulated cluster count.
> 
> if the zero/non-zero state changes very frequently, it will not work.

It will work, but just not improving anything. I think this is a worthwhile
optimzation to do.

Fam