Re: balance interrupts

[Stephen Satchell]

OK, color me stupid.  I just grepped the entire Documentation directory
for 2.6.0-test11, and couldn't find anywhere where the number of disk
requests for swap, or the swap transfer volume, is provided.  In 2.4 I
had a single place where all swap activity (whether it was to a separate
partition or to a file on a mounted file system) is recorded.

I also grepped /fs/proc for "swap" and "Swap" and didn't find anything
that had to do with swap request accounting, only with swap memory
allocation (which I do use, but which for me is only half the story).

My purpose for wanting this performance metric is to try to detect when
a server has entered a thrashing mode (lots of swaps for an extended
period of time, possibly coupled with an ever-increasing amount of swap
used as the server falls further and further behind) so that I can take
some form of corrective action before the OOM killer starts committing
processicide, perhaps incorrectly.

Now, I could try to identify swap partitions using /proc/swaps,
totalling up the RIO+WIO and RBLK+WBLK from /proc/diskinfo for those
partitions that are swap partitions to get some measure, but that
doesn't help when an after-the-build swap file is added because the
original swap partition is too small.

Someone please point out the obvious oversight to this feeble old fool
of a programmer.

Stephen Satchell


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