I posted last month about i/o elevators. Turns out that wasn't our problem at all. SuSE has found that it is the vm.swappiness = 0 causing kernels > 3.0.31 to go loopy here on some of our apps (particularly WMB and the DM for WAS) (loopy = i/o rates of 4000-6000 sec and unresponsive).
The kernel change was this http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=fe35004fbf9eaf67482b074a2e032abb9c89b1dd We have been using 0 because preemptive swapping really makes no sense when your swap space is in z/VM vdisk. Why page something in that's probably already on z/VM's page area, move it to a Linux page then let Linux move it to a vdisk page, which is in z/VM memory and which will end right back out on z/VM page space. We had a sles 9 problem a few years ago where some critical servers would slowly march through all of their swap space until they ran out. Setting swapiness to zero solved that problem. It seems also to have kept down the amount of z/VM page space we require in our overcommitted dev / test environment. Is anyone else using 0? If so, keep this in mind if you upgrade kernels! What do the rest of you think of this change? I will be doing some testing at numbers like 5 to see how that works out. Marcy Cortes This message may contain confidential and/or privileged information. If you are not the addressee or authorized to receive this for the addressee, you must not use, copy, disclose, or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation. ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
