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
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