Re: [PATCH 06/11] xfs: deferred inode inactivation

Dave Chinner
2021-03-22T23:38:41Z

On Tue, Mar 16, 2021 at 08:47:29AM -0700, Darrick J. Wong wrote:
> On Tue, Mar 16, 2021 at 07:27:10AM +0000, Christoph Hellwig wrote:
> > Still digesting this. What trips me off a bit is the huge amount of
> > duplication vs the inode reclaim mechanism. Did you look into sharing
> > more code there and if yes what speaks against that?
>
> TBH I didn't look /too/ hard because once upon a time[1] Dave was aiming
> to replace the inode reclaim tagging and iteration with an lru list walk
> so I decided not to entangle the two.
>
> [1] https://lore.kernel.org/linux-xfs/20191009032124.10541-23-david@fromorbit.com/

I prototyped that and discarded it - it made inode reclaim much,
much slower because it introduced delays (lock contention) adding
new inodes to the reclaim list while a reclaim isolation walk was in
progress.

The radix tree based mechanism we have right now is very efficient
as only the inodes being marked for reclaim take the radix tree
lock and hence there is minimal contention for it...

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com