On Sun, Nov 22, 2009 at 10:44 PM, Mike Christie <micha...@cs.wisc.edu> wrote: > Erez Zilber wrote: >> On Thu, Nov 19, 2009 at 10:02 PM, Mike Christie <micha...@cs.wisc.edu> wrote: >>> Ulrich Windl wrote: >>>> On 19 Nov 2009 at 11:07, Erez Zilber wrote: >>>> >>>>> On Thu, Nov 19, 2009 at 9:38 AM, Ulrich Windl >>>>> <ulrich.wi...@rz.uni-regensburg.de> wrote: >>>>>> Hi! >>>>>> >>>>>> Wouldn't it be more obvious to calculate the average delay to a ping >>>>>> request? >>>>>> (Possibly exponential average as for the system loads) (min and Max >>>>>> would be good >>>>>> as well, but standard deviation probably requires use of the FPU, so >>>>>> that's not >>>>>> possible in kernel modules (AFAIK)). >>>>> It's in userspace, so (almost) everything is possible. It's nice to >>>>> have counters, average delay etc, but I want to be able to know >>>>> exactly when bad things almost happened (i.e. timeout almost expired). >>>>> Counters/average delay will not help me. >>>> I thought you want to tune the timeouts. So if properly tuned, the kernel >>>> will log >>>> when when your measurements are unusual (i.e. timeout exceeded). >>>> >>> I think that is what I wanted. I think Erez wants something a little >>> different, right Erez? >> >> I think that it would be nice if we had both: >> 1. The average delay of a ping request. >> 2. A list of ping requests that almost timed out with some helpful >> info (when was the ping sent and how much time until we got a >> response). With this information, you can understand and debug the >> whole system: you can check your target and see what caused it to be >> so slow on that specific time, you can see if your network was very >> busy during that time etc. >> > > I think this sounds good to me. >
Regrading the average delay of a ping request task - we need to have the average delay, but we're interested only in the average delay of pings that were sent lately (i.e. not pings that were sent a year ago). Am I right? I thought about having a cyclic array of delays in the kernel. It can hold the delays of the last X pings (e.g. X = 1000). Whenever the user runs 'iscsiadm -m session -s', this array will be sent to userspace and we can calc the average delay/standard deviation/whatever you want in userland. Comments? Erez -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to open-is...@googlegroups.com. To unsubscribe from this group, send email to open-iscsi+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/open-iscsi?hl=en.
