Messages in this thread | | | Date | Tue, 21 Jul 1998 17:28:05 +1000 | From | Richard Gooch <> | Subject | Re: [PATCH] New phys_addr() syscall |
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Raul Miller writes: > Albert D. Cahalan <acahalan@cs.uml.edu> wrote: > > There were plans to make mlock() available to normal users for > > cryptographic purposes. There would be a quota to protect the > > machine. If a user (or group of users) can get 1/32 of the pages > > below 16 MB, then the system can not allocate 128 kB for DMA. > > You'll eventually want to allow memory locked with this variation of > mlock to be migrated out of the DMA region (to deal with fragmentation > issues).
That may present an unacceptable cost to a RT application. Copying a page can easily take 100 microseconds. If Linux ever has the ability to pin a RT process to a CPU, that process should never be delayed if it doesn't ask to I/O (assuming it's mlock(2)ed all it's pages).
Moving to another physical page is contrary to the spirit of mlock(2), IMO.
Regards,
Richard....
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