svn commit: r270759 - in head/sys: cddl/compat/opensolaris/kern cddl/compat/opensolaris/sys cddl/contrib/opensolaris/uts/common/fs/zfs vm

[Andriy Gapon]

on 04/09/2014 04:18 Steven Hartland said the following:
> Indeed that would be interesting, but we might find that its quite memory size
> dependent given the scaling so confirming HW details would be nice too.
> 
> I'd also be interested to know who wins the free race between the VM and ARC
> when using that value.

BTW, I've written a small silly program that tests for a problem that affected
me in the distant past: http://people.freebsd.org/~avg/arc-vs-swap.c

It gobbles almost all of the memory and then just sits on it never accessing it
again.  At the same time it repeatedly reads blocks of data from a large file.
The idea is that eventually the unused memory should be pushed out to the swap
and the ARC is allowed to grow to accommodate for the data being read.

I run this program on a freshly booted system without any other applications.
Prior to r270759 the system behaves as expected.  Although the pace of shifting
balance between the ARC and the swap-backed pages is quite slow.
After r270759 and with the default tuning the ARC always sits at its minimum
size.  To me this is a regression.

To summarize: I really appreciate the improvements that you are making here
https://reviews.freebsd.org/D702
Thanks!

P.S.
I wish there was an easy way to make the page cache and the ARC aware of each other.
-- 
Andriy Gapon