Please don't top-post it's hard to follow.
On Monday, May 09, 2011 03:07:57 PM Ali Ahsan wrote:
Thanks for reply,I dont know it has some thing to do with linux scheduler but some on suggested about linux scheduler cat /sys/block/sda/queue/scheduler there are quite few of them noop [anticipatory] deadline cfq.I have changed from cfq default to anticipatory,Now problem is less for me kswapd0 take 10-50% of cpu in very short bust less then milliseconds.Also i have changed /proc/sys/vm/pagecache from 100 to 10.
This means that you're limiting the amount of RAM that can be used as pagecache (basically caching I/O) to 10%. This may not be an issue for you but may also severely limit your performance (all depending on work load).
An alternative may be to simple set swappiness to 0.
Any more suggestion will help me make server better,As for i have read the best scheduler for databases are deadline like for mysql it worked great.
You'll really have to try them to know what works for you. The two main variables that'll affect the choice is your I/O load and the device under (type of raid for example). For example some raid controllers really prefer noop.
Lastly, you didn't tell us if you're on i386-pae or x86_64 which may make a big difference.
/Peter
On 05/09/2011 06:01 PM, Peter Kjellström wrote:
On Saturday, May 07, 2011 09:35:48 PM Ali Ahsan wrote:
Hi All
I have xeon server with 16 Gb Ram and no Swap memory.I am running cassandra server on two node in cluster.When there is high load on server kswapd0 kicks inn and take 100% cpu and make machine very slow and we need to restart out cassandra server.I have latest kernel 2.6.18-238.9.1.el5.Please let me know how can i fix this issue .Its hurting us badly this our production server any quick help will be appreciated.
There is more than one bug that causes this behaviour. A few related memory managent situations (possibly responsible) may actually be avoided if you add some swap (even if it's not used). My suggestion would be to add some swap, set swappiness to 0 and see what happens.
/Peter