Re: ~500 megs cached yet 2.6.5 goes into swap hell

[Lincoln Dale]

At 02:51 AM 30/04/2004, Andy Isaacson wrote:
> What I want is for purely sequential workloads which far exceed cache
> size (dd, updatedb, tar czf /backup/home.nightly.tar.gz /home) to avoid
> thrashing my entire desktop out of memory.  I DON'T CARE if the tar
> completed in 45 minutes rather than 80.  (It wouldn't, anyways, because
> it only needs about 5 MB of cache to get every bit of the speedup it was
> going to get.)  But the additional latency when I un-xlock in the
> morning is annoying, and there is no benefit.
>
> For a more useful example, ideally I *should not be able to tell* that
> "dd if=/hde1 of=/hdf1" is running. [1]  There is *no* benefit to cacheing
> more than about 2 pages, under this workload.  But with current kernels,
> IME, that workload results in a gargantuan buffer cache and lots of
> swapout of apps I was using 3 minutes ago.  I've taken to walking away
> for some coffee, coming back when it's done, and "sudo swapoff
> /dev/hda3; sudo swapon -a" to avoid the latency that is so annoying when
> trying to use bloaty apps.

the mechanism already exists; teach tar/dd and any other app that you don't 
want to pollute the page-cache with data with to use O_DIRECT.

i suspect updatedb is a different case as its probably filling the system 
with dcache/inode entries.


cheers,

lincoln.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/