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

[email protected]
Newsgroups gmane.linux.suse.oracle.general
Message-ID <OFF472FD9C.B8C188EC-ON83257561.00491876-83257561.004969F7@lomanegra.com.ar>
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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