Re: [PATCH RFC 0/2] btrfs: remove the metadata readahead mechanism

David Sterba
2021-12-07T14:53:48Z

On Tue, Dec 07, 2021 at 08:01:04PM +0800, Qu Wenruo wrote:
> On 2021/12/7 19:56, Filipe Manana wrote:
> > On Tue, Dec 07, 2021 at 07:43:49PM +0800, Qu Wenruo wrote:
> >> On 2021/12/7 19:02, Filipe Manana wrote:
> >>> On Tue, Dec 07, 2021 at 03:43:58PM +0800, Qu Wenruo wrote:
> >>>> This is originally just my preparation for scrub refactors, but when the
> >>>> readahead is involved, it won't just be a small cleanup.
> >>>>
> >>>> The metadata readahead code is introduced in 2011 (surprisingly, the
> >>>> commit message even contains changelog), but now only one user for it,
> >>>> and even for the only one user, the readahead mechanism can't provide
> >>>> much help in fact.
> >>>>
> >>>> Scrub needs readahead for commit root, but the existing one can only do
> >>>> current root readahead.
> >>>
> >>> If support for the commit root is added, is there a noticeable speedup?
> >>> Have you tested that?
> >>
> >> Will craft a benchmark for that.
> >>
> >> Although I don't have any HDD available for benchmark, thus would only
> >> have result from SATA SSD.

I'm doing some tests, in a VM on a dedicated HDD.