On Thursday 03 November 2005 21:26, Blaisorblade wrote: > > I was hoping that since the file was deleted from disk and is already > > getting _some_ special treatment (since it's a longstanding "poor man's > > shared memory" hack), that madvise wouldn't flush the data to disk, but > > would just zero it out. A bit optimistic on my part, I know. :) > > I read at some time that this optimization existed but was deemed obsolete > and removed. > > Why obsolete? Because... we have tmpfs! And that's the point. With > DONTNEED, we detach references from page tables, but the content is still > pinned: it _is_ the "disk"! (And you have TMPDIR on tmpfs, right?)
If I had that kind of control over environment my build would always be deployed in (including root access), I wouldn't need UML. :) (P.S. The default for Ubuntu "Horny Hedgehog" is no. The only tmpfs mount is /dev/shm, and /tmp is on / which is ext3. Yeah, I need to upgrade my laptop...) > I guess you refer to using frag. avoidance on the guest Yes. Moot point since Linus doesn't want it. > (if it matters for > the host, let me know). When it will be present using it will be nice, but > currently we'd do madvise() on a page-per-page basis, and we'd do it on > non-consecutive pages (basically, free pages we either find or free or > purpose). Might be a performance issue if that gets introduced with per-page granularity, and how do you avoid giving back pages we're about to re-use? Oh well, bench it when it happens. (And in any case, it needs a tunable to beat the page cache into submission or there's no free memory to give back. If there's already such a tuneable, I haven't found it yet.) Rob ------------------------------------------------------- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42" plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
