Disk I/O as a bottleneck?

[Omer Zak]

On Sun, 2011-05-08 at 09:47 +0300, Nadav Har'El wrote:
> On Sat, May 07, 2011, Omer Zak wrote about "Re: Disk I/O as a bottleneck?":
> > I suspect that speeding up /usr won't help improve performance that
> > much.  The applications, which seem to be sluggish, deal with a lot of
> > user data in /home.  Furthermore, this user data varies a lot with time,
> > hence it is not that good idea to store it in SSD.
> 
> As usual, "it depends on your workload" applies.
> 
> In my own personal experience (and naturally, it might differ considerably
> from your use case), when I see "sluggish behavior" on a desktop machine,
> what is actually happening is that "foreground" activity, such as playing or
> working with video files, or such as compilation of a large project, causes
> a lot of other pages to be swapped out; And then, when you switch to a
> different application, it needs to swap pages in - either program text (code)
> directly from the executables, or data pages from the swap partition.

I explicitly checked whether my PC is swapping or not (vmstat 1) and it
was not.  The sluggish behavior was not due to any RAM shortage.

The contents of /proc/sys/vm/swappiness are:
60

I did find (using iostat -x -k 1) that both /usr and /home are heavily
used (and %util hits 100% for both of them).  In my PC they are in
separate partitions but on the same hard disk (which is managed by LVM
with encryption, except for a smallish boot partition).

[OFFTOPIC] It was great experience to see all this thread resulting from
my single posting.  I can understand how it comes that some people enjoy
trolling mailing lists.  </wicked_grin>

--- Omer


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