I think there are 2 potential issues here.
The ZFS cache or ARC manages memory for all pools on a
system but the data is not really organized per pool. So on
a pool export we don't free up buffers associated with that
pool. The memory is actually returned to the system either
when pressure arises or on a modunload of the ZFS module; yep
that's a bit extreme.
So how about an rfe say:
6424665: "ZFS/ARC should cleanup more after itself"
That would have helped your scenario.
But I see another point here is that the "swap -d "
failed to exert the require memory pressure on ZFS.
Sounds like another bug we'd need to track;
-r
Daniel Rock writes:
> Roch Bourbonnais - Performance Engineering schrieb:
> > A already noted, this needs not be different from other FS
> > but is still an interesting question. I'll touch 3 aspects
> > here
> >
> > - reported freemem
> > - syscall writes to mmap pages
> > - application write throttling
> >
> >
> > Reported freemem will be lower when running with ZFS than
> > say UFS. The UFS page cache is considered as freemem. ZFS
> > will return it's 'cache' only when memory is needed. So you
> > will operate with lower freemem but won't actually suffer
> > from this.
>
>
> The RAM usage should be made more transparent to the administrator. Just
> today, after installing snv_37 on another machine, I couldn't disable swap
> because zfs has grabbed all free memory it could get and didn't release it
> (even after a "zfs export"):
>
> # swap -l
> swapfile dev swaplo blocks free
> /dev/md/dsk/d2 85,4 8 4193272 4193272
>
> # swap -s
> total: 275372k bytes allocated + 93876k reserved = 369248k used, 1899492k
> available
>
> # swap -d /dev/md/dsk/d2
> /dev/md/dsk/d2: Not enough space
>
> # kstat | grep pp_kernel
> pp_kernel 872514
>
> # prtconf | head -2
> System Configuration: Sun Microsystems i86pc
> Memory size: 4095 Megabytes
>
> # zpool export pool
> # zpool list
> no pools available
> # swap -d /dev/md/dsk/d2
>
> This was shortly after installation with not much running on the machine. To
> speed up 'mirroring' of swap I usually do the following (but couldn't in
> this case):
>
> swap -d /dev/md/dsk/d2
> metaclear d2
> metainit d2 -m d21 d22 0
> swap -a /dev/md/dsk/d2
>
>
>
>
> Daniel
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