Hacker News Reader

Comment by josteink | Hacker News Reader

Sounds really good. Particularly looking forward to native encryption and TRIM.

I couldn’t see it on the list, but I believe I’ve heard it mentioned before... Right now ZoL maintains its own cache, ARC and other things, besides what the Linux-kernel already provides, causing excess RAM usage.

Any news on that situation improving?

View on HN

>Any news on that situation improving?

This situation "improving" would be a performance regression, an afaik, no one is really looking to do anything about it. Managing its own caches are a feature, not a bug.

That memory is freeable if an application needs it so there's no harm in it being used, either.

But is it double buffering pages?

No, ZoL bypasses the usual page cache.

Is it doing it for mmap though? 2 years ago, it didn't double-buffer apart from mmaped files. Here's a note about priorities: https://news.ycombinator.com/item?id=11697901

Also seems to be solved in this port: https://www.crossmeta.io/another-zfs-port-on-linux/

Given that said port predates feature flags and has no source posted, making any assertions about what it actually does versus claims to do seems premature.

My problem is exactly that; something is periodically dropping a 16G cache...

It's still not great. Linux native caching keeps fighting with the ZFS cache and it's not quite as freeable as native cache. If you try to launch some applications that allocates big chunks of memory quickly, it may fail due to ZFS not freeing its memory fast enough. I had this issue before limiting the max ZFS cache size. If ZFS could integrate the caching better with Linux it would be perfect to me.

How does FreeBSD handles it?

Reply on news.ycombinator.com