[CentOS] Kernel update = slower ?

Thu Jun 1 23:40:11 UTC 2006
William L. Maltby <BillsCentOS at triad.rr.com>

On Thu, 2006-06-01 at 19:18 -0400, Sam Drinkard wrote:
> Johnny,
> 
>     After reading about the VM issue, I concur.  The previous kernel did 
> exhibit the behavior noted in the URL you sent.  Looking right now, I 
> see a considerable difference in use / swap.  The software running on 
> the machine generally uses anwhere from 1.2 > 1.4Gb of memory, and I had 
> noticed swap would, over time, increase, while there was still *some* 
> memory available, but it never would use totally all of it.  The 
> application running right now is a little different from the one that 
> runs late-night and after 16z, so I'll take a peek at it either tonight 
> if I'm up or in the a.m. after the thing starts.  I'll also note swap 
> and its size as time progresses to see if it increases as before with 
> free mem.

I forget the start of this thread... was 64 bit only? Anyway, I had my
32bit lock a couple times with symptoms like Sam mentions. Lots of swap
used and no reason for it. Was using lots of open browsers, a couple
different GUI MUAs, etc.

Turned off things I didn't need for this workstation behind firewall on
cable, like sendmail, spamc/d (started by evolution as it needs
regardless of system started), etc.

A *biggie*, maybe, is the stupid readahead and readahead_early stuff.
Take a look at their file lists. Some small % suits your needs, the rest
is just someone's idea of every possible thing that might speed up
initial response. I completely disable these and have seen no
difference. As I expected, after initial boot, most of it is wasted and
the "non-manual" memory management does a better job than someone who
probably got told "Make our boot faster than Windoze".

Up now for 6 days running similar load (I think, haven't bothered to
really measure it) and swap use is still good and response is still
good.

I suspect the heavy duty servers a lot of you have can also live without
these readahead* things. Put a stopwatch on it and see. YMMV.

> 
>     Thanks for the info.
> 

HTH
-- 
Bill
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