On Mon, Aug 14, 2017 at 7:18 AM, Paul Menzel <pmenzel@xxxxxxxxxxxxx> wrote: > Dear Cong, > > > Thank you for the response. > > > On 08/11/17 19:51, Cong Wang wrote: > >> On Fri, Aug 11, 2017 at 8:36 AM, Paul Menzel <pmenzel@xxxxxxxxxxxxx> >> wrote: >>> Or should some parameters be tuned? >>> >>> ``` >>> $ more /proc/sys/vm/min* >>> :::::::::::::: >>> /proc/sys/vm/min_free_kbytes >>> :::::::::::::: >>> 39726 >> >> >> >> Can you try to increase this? Although it depends on your workload, >> 38M seems too small for a host with 96+G memory. > > > Increasing the value to 128 MB did not get rid of the warning. With 256 MB > we were unable to reproduce the warning. Interesting. I wonder if we should just increase the hard-coded cap (64M) for the default min_free_kbytes, or make it configurable at compile-time. > >>> :::::::::::::: >>> /proc/sys/vm/min_slab_ratio >>> :::::::::::::: >>> 5 >>> :::::::::::::: >>> /proc/sys/vm/min_unmapped_ratio >>> :::::::::::::: >>> 1 >>> ``` >>> >>> There is quite some information about this on the WWW [1], but some >>> suggest >>> that with recent Linux kernels, this shouldn’t happen, as memory get >>> defragmented. >> >> >> >> On the other hand, the allocation order is 0 anyway. ;) > > > Right. Coherent(?) memory is not needed for an order of 0. > > In our case the memory is mainly occupied by the disk(?) buffer/cache, and > not the real program. So there is plenty available. Shouldn’t the Linux > kernel be able to deal with such situations, or is this exactly the use > case, which the parameter `min_free_kbytes` is for? Well, for atomic memory allocations, we can't wait for these memory to drain or reclaim, I think this is why min_free_kbytes exits. Atomic allocations are heavily used by networking, so the 64M cap is really not enough for a heavily loaded network server with a fast NIC. But I am not at all a MM expert. ;) -- 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
