Hi Andrea, Maciej, On 02/06/2017 03:17 AM, Andrea Reale wrote: > Hi Scott, > Hi all, > > in reply to the issues that Scott reported last month, myself and Maciej > investigated further by running quite a number of experiments on the > physical and virtual environments we have avaialable. > > We collected all the results and relevant logs in a Web page at > https://hotplug-tests.eu-gb.mybluemix.net/ so that anyone interested can > go there and check all the details. > > The tl;dr version is that, in all configuration, we could not reproduce > what Scott has described as "memory corruption". The only issue we > encountered happens when the system is booted with a small amount of > initial memory (e.g., mem=64M) and one tries to hot-add several sections > of memory in ZONE_MOVABLE; in that case, the process is likely to fail > when vmemmap tries to allocate chunks of 2^9 consecutive pages to make > space for the `struct page`s describing the new memory; in fact, it > seems likely that, in low memory situations, the system cannot find enough > consecutive pages in ZONE_DMA or ZONE_NORMAL. This condition is not > dependand on memory hot-plug; in fact, we counter-tested this by writing > a simple module that just tries to allocate a few chunks of 2^9 pages, > and we experienced that it fails when the system is booted with low > memory (sources and logs in the Web page linked above). > > @Scott: were your referring to this issue, by any chance, in your > previous emails? If not, we would really appreciate if you could help us > reproduce the condition you are experiencing and/or give us a more detail > of what are the symptoms of the corruption you are referring to.
One question regarding your patch posted here: https://lkml.org/lkml/2016/12/14/188 While the "hack" that sets/clears NOMAP in order for pfn_valid() to return false/true when appropriate during __add_pages() definitively does seem to work to probe the memory section, don't you also hit the same warning when you try to online that memory section in pages_correctly_reserved() once you have cleared the NOMAP flag? NB: I am working on the 4.1 kernel at the moment, but it seems to be nearly identical in that regard. > > We are still running additional tests on other boards and we will update > the Web page while we get them. If anyone happens to try these patches > on their system, we warmly invite to send feedback with either > negative or positive outcomes. I will definitively give this a try on ARM64 since I need to get it working there. Do you mind posting a non-RFC patch? Thanks! -- Florian
