Wow! [LWN.net]

Wow!

Posted Apr 19, 2007 14:58 UTC (Thu) by AnswerGuy (guest, #1256)
Parent article: ELC: How much memory are applications really using?

Having written an internal guide to "Understanding Memory Utilization" for
my current employer, developed courseware and taught numerous courses in advanced Linux systems administation (including sections on vmstat, top, slaptop etc) and having found, during my career as a consultant, many occasions to explain to programmers: "No, these systems don't need more memory and they are NOT swapping no matter what that top and free seem to be saying" ... with all that under my belt I can say:

Wow!

I'm so looking forward to having this incorporate into the mainstream. I
can scarcely imagine how much easier it will be to administer systems and
monitor memory capacity issues with these.

(Of course we'll still strive for a simple rule of thumb ... if you don't
have about half of your RAM available for caching ... you could probably
use a bit more in the system). :)

(I'm also looking forward to seeing the merge of I/O stats and atop compatible kernel patches that allow us to find the I/O hogs on a per process and per channel basis; that's been a, by far, the worst gap in
the performance analysis arsenal for Linux).

JimD

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Seconded

Posted Apr 20, 2007 7:05 UTC (Fri) by dion (subscriber, #2764) [Link]

I've always been somewhat confused that the default kernel couldn't provide the data atop needs to display IO stats, as that's one of the most useful things I've ever seen for tuning a Linux system.

I'm sorry to be somewhat redundant here, but I'd like to say a big "me too" on atop and memstats.

Wow!

Posted Apr 24, 2007 12:30 UTC (Tue) by jospoortvliet (subscriber, #33164) [Link]

Also a +1 from me. This information is hard to come by, and it's really wonderful we might see it available in the kernel by default.

Wow!

Posted Oct 26, 2007 22:28 UTC (Fri) by MarkSeger (guest, #35422) [Link]

Clearly this will all be a good thing and even though the memory stats aren't perfect, you CAN
look at memory and any other stats you want with the tool I build called collectl, which you
can get at http://collectl.sourceforge.net/

Collectl allows to to gather just about any of the major system performance metrics and
display then side-by-side or in more deal on multiple lines.  There's even a format that
allows you to put it in a format understandable by gnuplot.  Here's a simple example of just
looking at memory and disk

#<-----------Memory----------><-----------Disks----------->
#free buff cach inac slab  map KBRead  Reads  KBWrit Writes
  55M 552M   2G 532M    0    0      0      0       0      0
  55M 552M   2G 532M    0    0      0      0     220      6
  55M 552M   2G 532M    0    0      0      0       0      0

but there are far too many combinations to even try.  Check it out and see what you think.

btw - I chose to leave off time in the output above to save screen real estate but you can
easily add it in with a simple switch and if you want even more details, can include msec!
Why is this important?  Because collectl can run at sub-second intervals and if you care about
network stats and don't monitor at an interval of 0.9765 you'll lose accuracy.  If you don't
think that's true, I have a page on the website that goes into the details.

-mark

Wow!

Posted Oct 27, 2007 0:10 UTC (Sat) by nix (subscriber, #2304) [Link]

What a scarily useful-looking tool. Thank *you*.