On Wed, Oct 09, 2002 at 10:33:25AM +0200, Giuliano Pochini wrote:
> > The point of O_STREAMING is one change: drop pages in the pagecache
> > behind our current position, that are free-able, because we know we will
> > never want them.
> Does it drop pages unconditionally ? What happens if I do a
> streaming_cat largedatabase > /dev/null while other processes
> are working on it ? It's not a good thing to remove the whole
> cached data other apps are working on.
Anybody could make the cache thrash. I don't see this as an argument against
O_STREAMING (whether explicitly activated, or dynamically activated).
The only extension I would suggest (I don't think the patch did this?)
is that pages should only be candidates for being forgotten if all
open files associated with the page are O_STREAMING and all seek
points for all open files are beyond the page.
This would allow for a web app, or similar, that was serving the same
document over two different sockets, to provide a compromise between
O_STREAMING and not O_STREAMING where performance would suffer, but
for the common case, where only one person is accessing the file, the
full benefit of O_STREAMING would be realized.
Does the patch allow for mmap() to benefit from O_STREAMING?
"I intend to access this virtual memory range sequentially..."
mark
-- mark@mielke.cc/markm@ncf.ca/markm@nortelnetworks.com __________________________ . . _ ._ . . .__ . . ._. .__ . . . .__ | Neighbourhood Coder |\/| |_| |_| |/ |_ |\/| | |_ | |/ |_ | | | | | | \ | \ |__ . | | .|. |__ |__ | \ |__ | Ottawa, Ontario, CanadaOne ring to rule them all, one ring to find them, one ring to bring them all and in the darkness bind them...
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