On Thu, Nov 08, 2012 at 05:01:24PM +0000, Mel Gorman wrote: > (Sorry about being very late reviewing this) > > On Wed, Nov 07, 2012 at 03:01:28AM -0800, Anton Vorontsov wrote: > > This patch introduces vmpressure_fd() system call. The system call creates > > a new file descriptor that can be used to monitor Linux' virtual memory > > management pressure. There are three discrete levels of the pressure: > > > > Why was eventfd unsuitable? It's a bit trickier to use but there are > examples in the kernel where an application is required to do something like > > 1. open eventfd > 2. open a control file, say /proc/sys/vm/vmpressure or if cgroups > /sys/fs/cgroup/something/vmpressure > 3. write fd_event fd_control [low|medium|oom]. Can be a binary structure > you write > > and then poll the eventfd. The trickiness is awkward but a library > implementation of vmpressure_fd() that mapped onto eventfd properly should > be trivial. > > I confess I'm not super familiar with eventfd and if this can actually > work in practice You've described how it works for memory thresholds and oom notifications in memcg. So it works. I also prefer this kind of interface. See Documentation/cgroups/cgroups.txt section 2.4 and Documentation/cgroups/memory.txt sections 9 and 10. -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href