Messages in this thread | | | Date | Thu, 8 Nov 2012 19:14:22 +0200 | From | "Kirill A. Shutemov" <> | Subject | Re: [RFC 1/3] mm: Add VM pressure notifications |
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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
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