On Friday 21 December 2001 09:44 pm, Rik van Riel wrote:
> On Fri, 21 Dec 2001, Sasha Pachev wrote:
>
> > http://www.uwsg.iu.edu/hypermail/linux/kernel/0108.0/0675.html. I
> > adapted it to my kernel ( 2.4.17-rc2), disabled kswapd, did some
> > testing and noticed much better performance.
>
> This is very hard to believe.
>
> If kswapd does not run, it just means that _other_ processes
> will run the exact same code, only synchronously (instead of
> having kswapd do the cleanup for them).
That does make a difference. kswapd does its clean-up in a loop that runs
with very high priority every time it thinks that there are not enough free
pages. The process will only run this code if it actually fails to find a
free page, and if I understand correctly, do so with its regular priority,
right?
In my case, I do not mind if the process gets stuck looking for a free page
while letting other processes that already have all the pages they need run,
as opposed to kswapd monopolizing the CPU trying to clean up.
So, I would like to reiterate that kswapd disabling feature would be very
helpful to have in the kernel. It involves only trivial code changes, and it
does allow a sysadmin to do things a different way - like I said earlier,
Linux is about choice, and when it is possible, one should have it.
But actually, digging a little deeper - I think there is still a bug in
shrink_caches(). Even after disabling kswapd, in one instance I had a process
brutally murdered at the time when I had over 100MB of cache available. The
cache was heavily used and growing, if that helps any.
It must be noted that the one process murder in this case did not compare
with a massacre that happened in the same situation when kswapd was not
disabled. About 10 processes got killed.
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This archive was generated by hypermail 2b29 : Sun Dec 23 2001 - 21:00:27 EST