mjhjmtu

sudo echo ::memstat | sudo mdb -k
Usage Type/Subtype Pages Bytes %Tot %Tot/%Subt
---------------------------- ---------------- -------- ----- -----------
Kernel 291425 1.1g 17.5%
ZFS 844447 3.2g 50.7%

zfs is over 3G,but I have set ARC to consume max 2G

cat /etc/system
set zfs:zfs_arc_max = 2147483648
set zfs:zfs_arc_min = 1073741824

I have reboot of course.

Version is 11.4 beta

zfs_arc_max has apparently been deprecated. See https://docs.oracle.com/cd/E53394_01/html/E54818/chapterzfs-3.html#scrolltoc:

ZFS Memory Management Parameters

This section describes parameters related to ZFS memory management.

user_reserve_hint_pct

Description

Informs the system about how much memory is reserved for application
use, and therefore limits how much memory can be used by the ZFS ARC
cache as the cache increases over time.

By means of this parameter, administrators can maintain a large
reserve of available free memory for future application demands. The
user_reserve_hint_pct parameter is intended to be used in place of the
zfs_arc_max parameter to restrict the growth of the ZFS ARC cache.

Note - Review Document 1663862.1, Memory Management Between ZFS and
Applications in Oracle Solaris 11.2, in My Oracle Support (MOS) for
guidance in tuning this parameter. Data Type

Unsigned Integer (64-bit)

Default

0

If a dedicated system is used to run a set of applications with a
known memory footprint, set the parameter to the value of that
footprint, such as the sum of the SGA of Oracle database.

To assign a value to the parameter, run the script that is provided in
Document 1663862.1 in My Oracle Support (MOS). To make the tuning
persistent across reboots, refer to script output for instructions
about using –p option.

Range

0-99

Units

Percent

Dynamic

Yes

You can adjust the setting of this parameter dynamically on a running
system.

When to Change

For upward adjustments, increase the value if the initial value is
determined to be insufficient over time for application requirements,
or if application demand increases on the system. Perform this
adjustment only within a scheduled system maintenance window. After
you have changed the value, reboot the system.

For downward adjustments, decrease the value if allowed by application
requirements. Make sure to use decrease the value only by small
amounts, no greater than 5% at a time.

Commitment Level

Unstable

...

zfs_arc_max

Description

Determines the maximum size of the ZFS Adaptive Replacement Cache
(ARC). However, see user_reserve_hint_pct.

In my opinion, this is a huge step backwards. A hard limit is replaced with a mere "hint". There can be very, very, very good reasons for a hard limit.

(I'm wondering if there really is an undocumented ARC hard limit. Sun/Oracle has a history of doing things like that with ZFS. "ZFS is always consistent on disk! You don't need fsck or any debugging tools. No, you don't. WE SAID YOU DON'T. WHY OH WHY WON'T YOU BELIEVE US?!?! Oh, ummm, ahhh, yeah, here's zdb. We've been using it internally for years so it's pretty mature...")