Re: [PATCH 0/5] btrfs: scrub: improve the scrub performance

[Martin Steigerwald <martin@lichtvoll.de>]

David Sterba - 28.07.23, 18:50:37 CEST:
> On Fri, Jul 28, 2023 at 02:38:35PM +0200, Martin Steigerwald wrote:
> > Qu Wenruo - 28.07.23, 13:14:03 CEST:
> > > The first 3 patches would greately improve the scrub read
> > > performance, but unfortunately it's still not as fast as the
> > > pre-6.4 kernels. (2.2GiB/s vs 3.0GiB/s), but still much better
> > > than 6.4 kernels (2.2GiB vs 1.0GiB/s).
> > 
> > Thanks for the patch set.
> > 
> > What is the reason for not going back to the performance of the
> > pre-6.4 kernel? Isn't it possible with the new scrubbing method? In
> > that case what improvements does the new scrubbing code have that
> > warrant to have a lower performance?
> 
> Lower performance was not expected and needs to be brought back. A
> minor decrease would be tolerable but that's something around 5%, not
> 60%.

Okay. Best of success with improving performance again.

> > Just like to understand the background of this a bit more. I do not
> > mind a bit lower performance too much, especially in case it is
> > outweighed by other benefits.
> 
> The code in scrub was from 3.0 times and since then new features have
> been implemented, extending the code became hard over time so a bigger
> update was done restructuring how the IO is done.

Okay, thanks for explaining.

-- 
Martin