On 2014/6/20 18:30, David Rientjes wrote: > 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. > Hi David, You are right, if we echo 0x78000000 as the start_address_of_new_memory, the end_address_of_new_memory is exceeded the usable range. Thank you for your comments. My e820 map as follows: [ 0.000000] e820: BIOS-provided physical RAM map: [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable [ 0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved [ 0.000000] BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved [ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000007fffdfff] usable [ 0.000000] BIOS-e820: [mem 0x000000007fffe000-0x000000007fffffff] reserved [ 0.000000] BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved [ 0.000000] e820: remove [mem 0x40000000-0xfffffffffffffffe] usable [ 0.000000] NX (Execute Disable) protection: active [ 0.000000] e820: user-defined physical RAM map: [ 0.000000] user: [mem 0x0000000000000000-0x000000000009fbff] usable [ 0.000000] user: [mem 0x000000000009fc00-0x000000000009ffff] reserved [ 0.000000] user: [mem 0x00000000000f0000-0x00000000000fffff] reserved [ 0.000000] user: [mem 0x0000000000100000-0x000000003fffffff] usable [ 0.000000] user: [mem 0x000000007fffe000-0x000000007fffffff] reserved [ 0.000000] user: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved >> 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. You are right, it's not properly aligned to block_size_bytes. I have made a mistake. > >> 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. > I'm not clearly here, 0xfff0000000 is exceeded the usable range [mem 0x0000000000100000-0x000000007fffdfff] usable. So i think here should return "File exists", but it succeeded. Is it properly ? Best regards! > . > -- 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>