Messages in this thread | | | Date | Tue, 30 Jan 2001 02:18:47 +0000 (GMT) | From | James Sutherland <> | Subject | Re: Linux Disk Performance/File IO per process |
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On Mon, 29 Jan 2001, List User wrote:
> Just wanted to 'chime' in here. Yes this would be noisy and will have > an affect on system performance however these statistics are what are > used in conjunction with several others to size systems as well as to > plan on growth. If Linux is to be put into an enterprise environment > these types of statistics will be needed. > > When you start hooking up 100's of 'physical volumes' (be it real > disks or raided logical drives) this data helps you pin-point > problems. I think the idea of having the ability to turn such > accounting on/off via /proc entry a very nice method of doing things.
Question: how will the extra overhead of checking this configuration compare with just doing it anyway?
If the code ends up as:
if (stats_enabled) counter++;
then you'd be better off keeping stats enabled all the time...
Obviously it'll be a bit more complex, but will the stats code be able to remove itself completely when disabled, even at runtime??
Might be possible with IBM's dprobes, perhaps...?
> That way you can leave it off for normal run-time but when users > complain or DBA's et al you can turn it on get some stats for a couple > hours/days whatever, then turn it back off and plan an upgrade or > re-create a logical volume or stripping set.
NT allows boot-time (en|dis)abling of stats; they quote a percentage for the performance hit caused - 4%, or something like that?? Of course, they don't say whether that's a 486 on a RAID array or a quad Xeon on IDE, so the accuracy of that figure is a bit questionable...
James.
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