Re: kern/56329: nvme(4) takes long time to umount

[Christos Zoulas <christos%zoulas.com@localhost>]

But should't be something applying backpressure so that the number of vnodes to be recycled is kept reasonably sized?

christos

> On Apr 25, 2022, at 10:05 AM, J. Hannken-Illjes <hannken%mailbox.org@localhost> wrote:
> 
> The following reply was made to PR kern/56329; it has been noted by GNATS.
> 
> From: "J. Hannken-Illjes" <hannken%mailbox.org@localhost>
> To: NetBSD GNATS <gnats-bugs%netbsd.org@localhost>
> Cc: 
> Subject: Re: kern/56329: nvme(4) takes long time to umount
> Date: Mon, 25 Apr 2022 16:02:40 +0200
> 
> With help from Paul Goyette I'm able to reproduce the behaviour here.
> 
> - It is not related to nvme, it depends on the number of cached
>   vnodes, 3456591 in the last run taking ~7 seconds.
> 
> - With 64GByte memory my test machine takes ~6 seconds to unmount
>   a file system with 3332133 cached vnodes with "ld at virtio".
> 
> - This time to unmount didn't change in the last 7 years, testing
>   kernels from October 2014, 2015 ... until now it always took 5 +- 1
>   seconds to unmount.
> 
> - Latest run took 5.864 seconds, 1.311 were spent in cache_purgevfs(),
>   0.290 in VFS_SYNC() and 4.263 in vflush().
> 
> To me this doesn't look like a regression and recycling ~570000 vnodes
> per second looks ok.
> 
> --
> J. Hannken-Illjes - hannken%mailbox.org@localhost
>