Freebsd 11.0 - system freeze on intensive I/O

[Gautam]

Hi,

On Wed, Aug 9, 2017 at 7:43 PM, Mark Millard <markmi at dsl-only.net> wrote:

>
> Swap files on ZFS are also known to have the problem.
>
> Quoting bugzilla 206048's comment #7 (which is quoting an older
> list message):
>
> On 2017-Feb-13, at 7:20 PM, Konstantin Belousov <kostikbel at gmail.com>
> wrote
> on the freebsd-arm list:
>
> . . .
>
> swapfile write requires the write request to come through the filesystem
> write path, which might require the filesystem to allocate more memory
> and read some data. E.g. it is known that any ZFS write request
> allocates memory, and that write request on large UFS file might require
> allocating and reading an indirect block buffer to find the block number
> of the written block, if the indirect block was not yet read.
>
> As result, swapfile swapping is more prone to the trivial and unavoidable
> deadlocks where the pagedaemon thread, which produces free memory, needs
> more free memory to make a progress.  Swap write on the raw partition over
> simple partitioning scheme directly over HBA are usually safe, while e.g.
> zfs over geli over umass is the worst construction.
>
> ​Firstly, thanks all for the responses.

I just want to comment, that when I tested it there
was absolutely no need for any swap usage. I tried the test on a laptop
with 8GB RAM and
did it from the console mode. But it does seem that there might be some
request (read/write) to swap which
​causes a lock up to the system.​

​Thanks,
Gautam
​