On 01/30/2014 11:33 AM, Andiry Xu wrote: > On Thu, Jan 30, 2014 at 11:25 AM, Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote: >> [adding linux-mm mailing list] >> >> On 01/30/2014 08:52 AM, Andiry Xu wrote: >>> Hi, >>> >>> In kernel-parameters.txt, there is following description: >>> >>> memmap=nn[KMG]$ss[KMG] >>> [KNL,ACPI] Mark specific memory as reserved. >>> Region of memory to be used, from ss to ss+nn. >> >> Should be: >> Region of memory to be reserved, from ss to ss+nn. >> >> but that doesn't help with the problem that you describe, does it? >> > > Actually it should be: > Region of memory to be reserved, from nn to nn+ss. > > That is, exchange nn and ss. Yes, I understand that that's what you are reporting. I just haven't yet worked out how the code manages to exchange those 2 values. >> >>> Unfortunately this is incorrect. The meaning of nn and ss is reversed. >>> For example: >>> >>> Command Expected Result >>> memmap 2G$6G 6G - 8G reserved 2G - 8G reserved >>> memmap 6G$2G 2G - 8G reserved 6G - 8G reserved >> >> Are you testing on x86? >> The code in arch/x86/kernel/e820.c always parses mem_size followed by start address. >> I don't (yet) see where it goes wrong... >> > > Yes, it's a x86 machine. > >> >>> Test kernel version 3.13, but I believe the issue has been there long ago. >>> >>> I'm not sure whether the description or implementation should be >>> fixed, but apparently they do not match. >> >> I prefer to change the documentation and leave the implementation as is. >> > > That's fine. memmap itself works OK, it's just the description is > wrong and people like me get confused. > > Thanks, > Andiry -- ~Randy -- 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>