Re: [suse-oracle] File system cache limits, vm.dirty_ratio

I didn't have as much luck with swappiness, but would suggest trying it. From what I saw in the kernel source code, it should help. As an alternative to hugepages, you can also try the init.ora parameter LOCK_SGA. It is OS dependent and I think it is supported on SUSE 9 and 10, though I've never used it there. Hugepages is better with large memory but does take more time to calculate and implement.

 

http://www.dba-oracle.com/p_lock_sga.htm

 

 

 

 

 

From: Bobby Keegan [mailto:[email protected]] 
Sent: Wednesday, February 18, 2009 9:05 AM
To: [email protected]; Vladimir Barac
Cc: [email protected]; [email protected]
Subject: Re: [suse-oracle] File system cache limits, vm.dirty_ratio

 

We had something similar a year ago, we're on SuSE 9.  We adjusted the /proc/sys/vm/swapiness to 10 and it made a significant difference.

 

I couldn't find the original reference that we used but here are two. The one thing I remember is don't set it to zero.

 

http://aplawrence.com/Linux/memory_tuning.html

http://www.linuxjournal.com/article/8308

 

Bobby 

Oracle DBA

________________________________

From: [email protected] [mailto:[email protected]] On Behalf Of [email protected]
Sent: Wednesday, February 18, 2009 8:22 AM
To: Vladimir Barac
Cc: [email protected]; '[email protected]'
Subject: Re: [suse-oracle] File system cache limits, vm.dirty_ratio

 


The last year we had the same issue with Tivoli Data Protector, in our case we set the parameter vm.nr_hugepages to avoid Oracle SGA swapping during online backups and tune some parameters for Tivoli. 
After that we reduce swapping but it doesn't disappear. 

Regards! 

________________________________
Herman Maseberg
Líder de Tecnología
Loma Negra C.I.A.S.A.
Tel: (54-11)4319-3075
[email protected]


[email protected] escribió el 18/02/2009 09:15:18:

> We want to limit amount of memory that SLES uses to buffer file 
> systems. We have situation like this on our database server: 
>   
> - SGA at around half of physical memory (SGA 16GB, total RAM 32GB) 
> - Remaining memory is for user sessions 
> - No swapping, everything is fine. Performance is great, no issues. 
>   
> However, when we initiate backup (NetBackup client, simple file 
> backups) memory usage peaks at 100% and swapping starts. When we 
> terminate backup, everything slowly goes back to normal. 
>   
> Our assumption is that file system caching kicks in when we start 
> backup. We want to limit O/S cache for filesystems. Oracle doesn't 
> use file system cache anyway, so it will not affect Oracle (OCFS2 
> with O_DIRECT). 
>   
> vm.dirty_ratio is set to 10, as advised by Suse support. However, 
> nothing has changed. This is free output: 
>   
> free -m 
>              total       used       free     shared    buffers     cached 
> Mem:         32173      32107         65          0         66      25896 
> -/+ buffers/cache:       6145      26028 
> Swap:        32773        578      32194 
>   
> Also, paging rate increases tremendously. Here is the part of sar output: 
>   
> sar -B 5 20 
> Linux 2.6.16.46-0.12-smp (ai-sapgrt-pr1)        02/18/09 
>   
> 12:23:42     pgpgin/s pgpgout/s   fault/s  majflt/s 
> 12:23:47     64715.80    916.60  13664.40      0.00 
> 12:23:52     59247.31    710.98  12509.38      0.00 
> 12:23:57     32867.47   1010.58  11054.29      0.00 
> 12:24:02     49332.20    221.20  23691.20      0.00 
> 12:24:07     43291.97   1972.89  12452.41      0.20 
> 12:24:12     52531.94   1495.21  11647.31      0.00 
>   
> 12:24:12     pgpgin/s pgpgout/s   fault/s  majflt/s 
> 12:24:17     30538.00   1095.80  13729.20      0.80 
> 12:24:22     35545.00   2260.80  15230.00      0.20 
> 12:24:27     59802.40   1898.80  15587.80      0.00 
> 12:24:32     46216.57   2165.07  13352.69      1.00 
> 12:24:37     44167.60   4573.20  13011.20      2.20 
> 12:24:42     44947.40   2124.00  12552.80      0.20 
>   
> Is there a way to really limit Linux buffers? 
>   
> Regards, 
> Vladimir Barac
> Database administrator | Alghanim Industries
> P.O. Box 223, Safat 13003, Kuwait
> Tel: +965 1881 111  / ext. 2960 
> [imagen eliminada] 
>   
> 
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