Bug #12858
closed
Please adjust swap usage to meet reality
100%
Description
I used to think memory hunger is one of the attribute of Illumos and think it's usual, but it turned out to be wrong. After tried OmniOS and DilOS, I would say OI's way of using swap is too abusive. On a clean system just started up without doing anything, both top and System Monitor report about swap space being used. It's not much but increased over time to about a hundred of mb of swap. Especially when heavy task being done, e.g: install large amount of packages with pkg. Fortunately, OI does release most of the swap space after the operation was completed. But I have never seen OI without using swap. On contrary, both OmniOS and DilOS rarely used any swap at all, even after heavy operation like install a large amount of packages.
On all of these Illumos systems, I have limited the zfs max arc to 512 mb. The VirtualBox VM configuration I used for all of them is the same: 4G ram, 64G Disk and 4 cpu cores.
I have some questions to ask:
1. Is there anything equivalent to Linux's swapiness to adjust the OS's way of using swap?
2. On top's result, does used ram already included zfs arc cache or not?
3. On System Monitor's result, does used ram already included zfs arc cache or not?
Updated by giahung 1997tn over 3 years ago
giahung 1997tn wrote:
I used to think memory hunger is one of the attribute of Illumos and think it's usual, but it turned out to be wrong. After tried OmniOS and DilOS, I would say OI's way of using swap is too abusive. On a clean system just started up without doing anything, both top and System Monitor report about swap space being used. It's not much but increased over time to about a hundred of mb of swap. Especially when heavy task being done, e.g: install large amount of packages with pkg. Fortunately, OI does release most of the swap space after the operation was completed. But I have never seen OI without using swap. On contrary, both OmniOS and DilOS rarely used any swap at all, even after heavy operation like install a large amount of packages.
On all of these Illumos systems, I have limited the zfs max arc to 512 mb. The VirtualBox VM configuration I used for all of them is the same: 4G ram, 64G Disk and 4 cpu cores.
I have some questions to ask:
1. Is there anything equivalent to Linux's swapiness to adjust the OS's way of using swap?
2. On top's result, does used ram already included zfs arc cache or not?
3. On System Monitor's result, does used ram already included zfs arc cache or not?
I forgot to update: If you said used memory is not wasted memory, I have to disagree. OI used swap when top and System Monitor both report the system still have plenty of ram. Even when just started up and no addition applications were started, OI already used swap.
Updated by Olaf Bohlen about 3 years ago
- Status changed from New to Rejected
- Assignee set to Olaf Bohlen
- Priority changed from Normal to Low
Hi,
I'm rejecting this as a bug, as it is not. Please also consider writing to oi-discuss Mailinglist for asking further questions: https://openindiana.org/mailman/listinfo
So first of all, the Linux kernel and the illumos kernel use different memory management. Especially when creating new processes we need the address-space of the swap device, we do not really write to it. That is the reason why we create a swap volume.
I'm not aware of any equivalents to Linux swapiness, as mentioned before: the kernel behave very different, for example we also have no OOM, as we could never run into such a scenario, as we always ensure we have the addresses a process requests.
If you want to analyze memory usage, I'd recommend running echo ::memstat | mdb -k as root, it will print out the memory distribution in your system:
(593) x230:/root# echo ::memstat | mdb -k Page Summary Pages MB %Tot ------------ ---------------- ---------------- ---- Kernel 748883 2925 18% Boot pages 137 0 0% ZFS File Data 2133407 8333 52% Anon 1000724 3909 24% Exec and libs 6821 26 0% Page cache 49282 192 1% Free (cachelist) 16819 65 0% Free (freelist) 152926 597 4% Total 4108999 16050 Physical 4108998 16050
So in this system the ARC consumes about 8G RAM, user processes (anon) about 3.9G and the Kernel itself 2.9G
We have around 600MB really free RAM that can be assigned immediatly.
Regards,
Olaf