Ben,

Would you be able make a build that I could test this on OmniOS r151014?
I'd love to test this out.

This seems to be exactly the tuning knob I need in my environment.   All my
pools are 0.4 - 1 PB in size with billions of files. Metadata performance
is always an issue for us even with secondarycache=metadata.  It never
seems to get enough metadata into L2ARC.

-Chip

On Tue, Nov 29, 2016 at 6:52 PM, Matthew Ahrens <[email protected]>
wrote:

> *@ahrens* requested changes on this pull request.
>
> Overall, I am not comfortable making this semantic change without more
> extensive real-world testing. I would suggest that you get someone who uses
> L2ARC in production on general-purpose workloads (or a wide variety of
> workloads) to at least review this code, and better yet to test it.
> Unfortunately I (and Delphix) do not use L2ARC so we aren't in a good
> position to test this.
> ------------------------------
>
> In usr/src/uts/common/fs/zfs/arc.c
> <https://github.com/openzfs/openzfs/pull/189#pullrequestreview-10672665>:
>
> > @@ -2931,9 +2943,34 @@ arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t 
> > *hash_lock)
>       return (bytes_evicted);
>  }
>
> +/*
> + * Based on l2arc_spa_list, returns true if the
> + * given spa has an alive (!dead) L2 device,
> + * false otherwise.
> + */
> +static boolean_t
> +l2arc_alive(uint64_t spa)
>
> Could you do this by walking the existing l2arc_dev_list? This mechanism
> seems quite complicated.
>
> That said, I'd be concerned about the performance of this either way, it's
> in a pretty hot path.
>
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