On Tue, Sep 21, 2021 at 10:03:49AM +0100, Christoph Hellwig wrote:

On Tue, Sep 21, 2021 at 09:06:35AM +1000, Dave Chinner wrote:

quoted

On Fri, Sep 17, 2021 at 06:30:10PM -0700, Darrick J. Wong wrote:

quoted

From: Darrick J. Wong <djwong@kernel.org>

Replace the statically-sized btree cursor zone with dynamically sized
allocations so that we can reduce the memory overhead for per-AG bt
cursors while handling very tall btrees for rt metadata.

Hmmmmm. We do a *lot* of btree cursor allocation and freeing under
load. Keeping that in a single slab rather than using heap memory is
a good idea for stuff like this for many reasons...

Or rather a few slabs for the different kind of cursors.  But otherwise
agreed.

I think I prefer to let Chandan decide if there are going to be enough
heavily fragmented files to warrant a second slab for maxlevels>9 files.
We should probably be selective about which cursor maxheight we want to
use depending on whether or not the file really needs it.

--D