On Thu, Aug 10, 2006 at 01:02:54AM -0700, Andrew Morton (akpm@osdl.org) wrote:

quoted

quoted

Afaict this mmap function gives a user a free way of getting pinned memory. 
What is the upper bound on the amount of memory which a user can thus
obtain?

it is limited by maximum queue length which is 4k entries right now, so
maximum number of paged here is 4k*40/page_size, i.e. about 40 pages on
x86.

Is that per user or per fd?  If the latter that is, with the usual
RLIMIT_NOFILE, 160MBytes.  2GB with 64k pagesize.  Problem ;)

Per kevent fd.
I have some ideas about better mmap ring implementation, which would
dinamically grow it's buffer when events are added and reuse the same
place for next events, but there are some nitpics unresolved yet.
Let's not see there in next releases (no merge of course), until better 
solution is ready. I will change that area when other things are ready.

-- 
	Evgeniy Polyakov