On 2014/6/12 15:07, David Rientjes wrote: > On Thu, 12 Jun 2014, Zhang Zhen wrote: > >>>> % echo start_address_of_new_memory count_of_sections > /sys/devices/system/memory/probe >>>> >>>> Then, [start_address_of_new_memory, start_address_of_new_memory + >>>> count_of_sections * memory_block_size] memory range is hot-added. >>>> >>>> If this proposal is reasonable, i will send a patch to realize it. >>>> >>> >>> The problem is knowing how much memory is being onlined so that you can >>> definitively determine what count_of_sections should be. The number of >>> pages per memory section depends on PAGE_SIZE and SECTION_SIZE_BITS which >>> differ depending on the architectures that support this interface. So if >>> you support count_of_sections, it would return errno even though you have >>> onlined some sections. >>> >> Hum, sorry. >> My expression is not right. The count of sections one time hot-added >> depends on sections_per_block. >> > > Ok, so you know specifically what sections_per_block is for your platform > so you know exactly how many sections need to be added. > >> Now we are porting the memory-hotplug to arm. >> But we can only hot-add *fixed number of sections one time* on particular architecture. >> >> Whether we can add an argument on behalf of the count of the blocks to add ? >> >> % echo start_address_of_new_memory count_of_blocks > /sys/devices/system/memory/probe >> >> Then, [start_address_of_new_memory, start_address_of_new_memory + count_of_blocks * memory_block_size] >> memory range is hot-added. >> > > As I said, if the above returns errno at some point, it still can result > in some sections being onlined. To be clear: if > "echo 0x10000000 > /sys/devices/system/memory/probe" fails, the section > starting at address 0x10000000 failed to be onlined for the reason > specified by errno. If we follow your suggestion to specify how many > sections to online, if > "echo '0x10000000 16' > /sys/devices/system/memory/probe" fails, eight > sections could have been successfully onlined at address 0x10000000 and > then we encountered a failure (perhaps because the next sections were > already onlined, we get an -EEXIST). We don't know what we successfully > onlined. > > This could be mitigated, but there would have to be a convincing reason > that this is better than using the currently functionally in a loop and > properly handling your error codes. Hi David, I think you are right. We had better to use the currently functionally in a loop if we need to add several blocks. In this way, we can get an errno in time if a block failed to be onlined. Thanks for your comments. I got it. > > -- > 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> > > -- 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>