On Wed, Nov 07, 2012 at 02:11:10PM +0200, Kirill A. Shutemov wrote: [...] > > We can have plenty of "free" memory, of which say 90% will be caches, > > and say 10% idle. But we do want to differentiate these types of memory > > (although not going into details about it), i.e. we want to get > > notified when kernel is reclaiming. And we also want to know when the > > memory comes from swapping others' pages out (well, actually we don't > > call it swap, it's "new allocations cost becomes high" -- it might be a > > result of many factors (swapping, fragmentation, etc.) -- and userland > > might analyze the situation when this happens). > > > > Exposing all the VM details to userland is not an option > > IIUC, you want MemFree + Buffers + Cached + SwapCached, right? > It's already exposed to userspace. How? If you mean vmstat, then no, that interface is not efficient at all: we have to poll it from userland, which is no go for embedded (although, as a workaround it can be done via deferrable timers in userland, which I posted a few months ago). But even with polling vmstat via deferrable timers, it leaves us with the ugly timers-based approach (and no way to catch the pre-OOM conditions). With vmpressure_fd() we have the synchronous notifications right from the core (upon which, you can, if you want to, analyze the vmstat). >> 2. The last time I checked, cgroups memory controller did not (and I guess >> still does not) not account kernel-owned slabs. I asked several times >> why so, but nobody answered. > > Almost there. Glauber works on it. It's good to hear, but still, the number of "used KBs" is a bad (or irrelevant) metric for the pressure. We'd still need to analyze the memory in more details, and "'limit - used' KBs" doesn't tell us anything about the cost of the available memory. Thanks, Anton. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
