Re: [PATCHSET 3/3] xfsprogs: scale shards on ssds

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Jun 06, 2024 at 10:06:42PM -0700, Christoph Hellwig wrote:
> On Tue, Jun 04, 2024 at 05:56:36PM -0700, Darrick J. Wong wrote:
> > Not much other than the AG[IF] and log grant heads becoming less hot.
> > That pushes the bottlenecks to the storage device, which indeed is about
> > 8 per device.  More if you can raid0 them.
> > 
> > *Fortunately* for metadata workloads the logging code is decent about
> > deduplicating repeated updates, so unless you're doing something truly
> > nasty like synchronous direct writes to a directory tree with parent
> > pointers that is being modified heavily, it takes some effort to
> > overload the ssd.
> > 
> > (Or a crappy ssd, I guess.  Maybe I'll pull out the 860 QVO and see how
> > it does.)
> 
> Ok.  I'm also a little worried about creating lots of AGs for tiny
> file systems.  Then again I've not actually been able to find the code
> yet which I should probably look at first.

It shouldn't create fewer AGs than what the default algorithm would have
calculated, and it won't create AGs smaller than 4GB.

--D