On Fri, 20 Jun 2014, Zhang Zhen wrote: > Hi, > > I am testing mem-hotplug on a qemu virtual machine. I executed the following command > to notify memory hot-add event by hand. > > % echo start_address_of_new_memory > /sys/devices/system/memory/probe > > To a different start_address_of_new_memory I got different results. > The results are as follows: > > MBSC-x86_64 /sys/devices/system/memory # ls > block_size_bytes memory2 memory5 power > memory0 memory3 memory6 probe > memory1 memory4 memory7 uevent > MBSC-x86_64 /sys/devices/system/memory # echo 0x70000000 > probe Since block_size_bytes is 0x8000000 == 128MB, this is 0x70000000 / 0x8000000 = section number 14. Successfully hot added. Presumably you're reporting that there is no physical memory there, so this would default to the online node of the first memory block, probably node 0. > MBSC-x86_64 /sys/devices/system/memory # echo 0x78000000 > probe > -sh: echo: write error: File exists EEXIST gets returned when the resource already exists, mostly likely system RAM or reserved memory as reported by your BIOS. You report this is a 2GB machine, no reason to believe memory at 1920MB isn't already online (including reserved). > MBSC-x86_64 /sys/devices/system/memory # echo 0x80000000 > probe > -sh: echo: write error: File exists > MBSC-x86_64 /sys/devices/system/memory # echo 0x88000000 > probe > -sh: echo: write error: File exists Same. > MBSC-x86_64 /sys/devices/system/memory # echo 0x8f000000 > probe > -sh: echo: write error: Invalid argument Returns EINVAL because it's not a multiple of block_size_bytes, it's not aligned properly. > MBSC-x86_64 /sys/devices/system/memory # echo 0x90000000 > probe > -sh: echo: write error: File exists See above, the resoure already exists. Check your e820 your dmesg, which is missing from this report, to determine what already exists and may be already online or reserved. > MBSC-x86_64 /sys/devices/system/memory # echo 0xff0000000 > probe 0xff0000000 / 0x8000000 is section 510, successfully onlined. > MBSC-x86_64 /sys/devices/system/memory # ls > block_size_bytes memory2 memory510 probe > memory0 memory3 memory6 uevent > memory1 memory4 memory7 > memory14 memory5 power Looks good, you onlined sections 14 and 510 above. > MBSC-x86_64 /sys/devices/system/memory # echo 0xfff0000000 > probe Same for section 8190. > MBSC-x86_64 /sys/devices/system/memory # ls > block_size_bytes memory2 memory510 power > memory0 memory3 memory6 probe > memory1 memory4 memory7 uevent > memory14 memory5 memory8190 > Confirmed it's onlined. > The qemu virtual machine's physical memory size is 2048M, and the boot memory is 1024M. > > MBSC-x86_64 / # cat /proc/meminfo > MemTotal: 1018356 kB > MBSC-x86_64 / # cat /sys/devices/system/memory/block_size_bytes > 8000000 > That's irrelevant, you've explicitly onlined memory that doesn't exist. Not sure why you're using the probe interface unless you need it for x86, is ACPI not registering it correctly? > Three questions: > 1. The machine's physical memory size is 2048M, why echo 0x78000000 as the start_address_of_new_memory failed ? > Copy your e820 map from your dmesg, it's probably reserved or already online, this is lower than 2048M. > 2. Why echo 0x8f000000 as the start_address_of_new_memory, the error message is different ? > Not properly aligned to block_size_bytes. It's a nuance, but block_size_bytes is exported in hex, not decimal. > 3. Why echo 0xfff0000000 as the start_address_of_new_memory succeeded ? 0xfff0000000 has exceeded the machine's physical memory size. > You're telling the kernel differently. -- 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=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>