On Feb 25, 12:09pm, Ale Terlevich wrote:
> Subject: update
>
>
>   Hi,
>
>    I've recently nocied that update seems to be taking up too much CPU
> time according to top.
>
> I'm running a kernel compiled today, with the vm_update.c patched
> as announced in current-users today, and a SA110 CPU
>
>   It varies from 6% when it's 'sleeping' for its 30 seconds to upto 30 or
> even 50% when it 'wakes up'. When it does wake up, the whole machine
> freezes for about a second (At least typing into this xterm does) and
> when it unfreezes, I often get the last key pressed repeated many times
> over. It also doesn't seem to register keypresses while frozen.
>
>   Oh, another thing. I'm not actually doing anything to the filesystem at
> the mo, so syncing the disks isn't writing anything to them.
>
>   I don't think this happened with kernels compiled  ~2 weeks ago.
>
> Has anyone else experienced this with the latest source?  Can anyone shed
> light on this?

This is a problem with the StrongArm cache-cleaning. That is where all the CPU
time is going. A bug in sync was fixed a week or so ago such that it now works
properly. This has resulted in a lot more cache cleaning and the performance
hit you are seeing.

>   Are there any ramifications to running without update? (I'm using the
> machine mainly as an xterminal at the mo, i.e. not writing much to disk)

Basically all update does is to sync the disks. If you don't sync the disks
then the cached information won't get written back. Of course unmounting syncs
the disks, but if the machine crashes in the meantime you might have rather a
messy fsck to do.

Cheers

Rob