Excessive page-outs, even after memory upgrade

[Michael Steele_2]

Hi

Just out of curiosity, were you using secure path in contention with native load balancing provided in 11.31.

vxfsd is online jfs, I don't suppose you have any contention with raw logical volumes and online jfs file systems?

Since this is a HW product, HP will have to take full responsibility. Stop sweating it and throw it back as incompaitible / bugged.

[Andrew Scott_3]

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If you are only using 24% of physical memory you do not have any pageouts.

You might have pageins which are ok but not pageouts. You may be misunderstanding the output of the vmstat memory report. You will not get pageouts unless you are low on memory and all of it is used.
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I absolutely seeing seeing pageouts. Thousands per second, on a system with a low memory load but a very high I/O load.


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You might want to increase the amount of filecache_max
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It's currently set at 10%, which is 3.2GB. Since the size of the transaction files that are being applied here seldom exceed 500MB, and the actual filecache size is hovering around 2.8-3GB depending on the time of day. Does it make sense to increase it when it isn't using everything it's already allowed to use?

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How is your oracle databases setup. JFS filesystem, RAC with CFS or Raw Lvs ?
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Oracle data files on VXFS running over LVM on an EVA.

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These are separate/opposite. You could be up to 30% IO wait.
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Yes, that's what I was describing. The CPU can't go past 70% because it's sitting around waiting on I/O.

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How do you know the page-outs are for these processes?
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I don't know, that's what I'm trying to find out: what are the page-outs, and are they significant?

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Just out of curiosity, were you using secure path in contention with native load balancing provided in 11.31.
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Interesting question, I wasn't aware SecurePath even ran on 11.31, we're using the native multipath I/O.

We aren't using any raw volumes, everything is on a filesystem. Is vxfsd known to become a bottleneck in heavily laden systems?

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Since this is a HW product, HP will have to take full responsibility. Stop sweating it and throw it back as incompaitible / bugged.
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This statement confuses me. Are you suggesting I box it up and send it all back? Where do I transfer my workload?

[Don Morris_1 · Accepted solution]

vmstat reports file cache flushing of dirty pages as pageouts (because they are from a memory management point of view -- the memory management is simply being applied to a subset of the system [only the cache] instead of the system as a whole, and the backing store is your file system, not a swap device).

So with 0 actual swap used and high page outs -- it sounds to me that you've got high file cache utilization, causing a large amount of dirty page pushout. (Clean pages wouldn't register as pageouts nor cause I/O -- they'd just get dropped). Increasing your file cache might help to some extent -- but at the rates you're talking about it sounds more like you have workloads chewing through and dirtying significantly more memory than your file cache. Still -- since you say you're only 25% utilized, it certainly would be worth a shot to raise filecache_max and let those dirty pages stay in the cache longer.

And just to settle that topic -- pseudo-swap never, ever gets any time of page-out. Remember that it is an accounting trick at the reservation layer, not some sort of device. The pageout mechanism simply proceeds through the pageable set -- and anything that is all reserved from pseudo-swap gets skipped in consideration, anything partial will be considered but if the actual swap allocation fails, the pager daemon moves along.

[Andrew Scott_3]

Awesome information. I'll increase the filecache_max and see what that does to the system.

Thank you!

[Andrew Scott_3]

I increased the filecache_max from 10% to 15%. Immediately the page-outs dropped to 0 and the filecache started growing. Once it hit the new 4.8GB limit, the page-outs came back.

I think my question has been answered, thanks!

[Rita C Workman]

I hope didn't miss this ... but I didn't see some requested info.

Did you mention how much swapdisk you set up?

Can you provide the output for the following:

vmstat -nS 1 10
sar -v 1 10
swapinfo -tam

I'm also curious about parm values. You mentioned you have 32Gb mem and filecache_max set to 10%. What are the values for:

filecache_min
ninode
vx_ninode
Semmaphore parm values
shmmax (you mention 4Gb, could you post the exact value)
maxdsiz

/rcw

[Michael Steele_2]

Can you attach the page out report?

[Duncan Edmonstone]

Andrew,

for standby databases which I presume are just doing redo apply (essentially a slow synchronous write as the redo arrives over the network followed by a faster synchronous read as the redo is applied, one wonders whether you are gaining much by using the filesystem cache at all for the redo log and archive redo log filesystems...

if you have online jfs you might want to try mounting those filesystems configured for direct io only (filesystem mount options mincache=direct,convosync=direct) and see if that changes anything... you could event try the filesystems with the datafiles as well (oracle doesn't usually benefit that much from filesystem cahce)

HTH

Duncan

[Andrew Scott_3]

Rita:
The DBA's just shut down the instances to fiddle with something, so I don't have anything valid to give you for vmstat, sar, or swapinfo.

The rest:
filecache_min 1632595968 Default Auto
ninode 8192 Default
vx_ninode 0 Default Immed
shmmax 8192000000 8192000000 Immed
maxdsiz 1073741824 Default Immed
maxdsiz_64bit 4294967296 Default Immed

shmmax was increased from 4GB on a recommendation from Oracle.

Michael, I'll get something when they restart the databases.

Duncan,
There are three standby instances on this machine. One is a true standby that receives transactions from the primary asynchronously and applies them directly to the database.

The other two receive transaction logs from other machines via FTP, and then apply them directly to their respective standby instances. There are no redo or archive logs on this particular system, and the transaction logs are dumped onto the same filesystem as the standby database.