Re: [PATCH v6 00/12] qcow2: fix parallel rewrite and discard (lockless)

[Vladimir Sementsov-Ogievskiy]

22.04.2021 19:30, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
>
> It's an alternative lock-less solution to
>    [PATCH v4 0/3] qcow2: fix parallel rewrite and discard (rw-lock)
>
> In v6 a lot of things are rewritten.
>
> What is changed:
>
> 1. rename the feature to host_range_refcnt, move it to separate file
> 2. better naming for everything (I hope)
> 3. cover reads, not only writes
> 4. do "ref" in qcow2_get_host_offset(), qcow2_alloc_host_offset(),
>      qcow2_alloc_compressed_cluster_offset().
>     and callers do "unref" appropriately.


About performance. With these series we do extra allocations and hash-map 
operations.. Still testing by

./build/qemu-img bench -c 1000000 -s 4K --image-opts driver=null-co,size=5G

and

./build/qemu-img bench -c 1000000 -s 4K -w --image-opts driver=null-co,size=5G

I see difference less than 1%.


--
Best regards,
Vladimir