Re: [patch] vmfixes-2.4.0-test9-B2 - fixing deadlocks

Andrea Arcangeli
2000-09-27T13:56:08Z

On Wed, Sep 27, 2000 at 10:11:43AM +0200, Christoph Rohland wrote:
> I just checked one oracle system and it did not lock the memory. And I

If that memory is used for I/O cache then such memory should released when the
system runs into swap instead of swapping it out too (otherwise it's not cache
anymore and it could be slower than re-reading from disk the real data in
rawio).

> Customers with performance problems very often start with too little
> memory, but they cannot upgrade until this really big job finishes :-(
>
> Another issue about shm swapping is interactive transactions, where
> some users have very large contexts and go for a coffee before
> submitting. This memory can be swapped.

Agreed, that's why I said shm performance under swap is very important
as well (I'm not understimating it).

But again: if the shm contains I/O cache it should be released and not swapped
out. Swapping out shmfs that contains I/O cache would be exactly like swapping
out page-cache.

Andrea