On 10/24/17 at 01:31pm, Dave Young wrote: > crashkernel=range:size syntax allows to reserve specified size for system > with total memory fall into the specified range. For example: > crashkernel=2G-3G:128M,3G-:256M reserves 128M for system with memory >=2G > and memory <3G, and reserves 256M for system with memory >= 3G > > In the above case 256M as a fixed value which can not fulfill very huge > systems with large memory and IO devices. As memory size increases usually > minimum memory requirement for booting will also increase. It is nearly > impossible for a kernel to run with a fixed limited memory size for all > kinds of systems. > > Thus extend the crashkernel=range:size to let user specify the scaling > ratio in kernel cmdline like below: > crashkernel=range:size^order, for example: > crashkernel=2G-:128M^14 reserve 128M + (total_memory - 128M) >> 14 > for machines with over 2G memory.
Well, ah.., this look a little ugly and tricky. Leave this to other reviewers to comment. > > Also s/start-[end]/[start]-end/ in kernel-parameters.txt according to code > > Signed-off-by: Dave Young <[email protected]> > --- > Documentation/admin-guide/kernel-parameters.txt | 10 ++++-- > Documentation/kdump/kdump.txt | 7 ++-- > kernel/crash_core.c | 35 > +++++++++++++++++++++--- > 3 files changed, 41 insertions(+), 11 deletions(-) > > --- linux-x86.orig/kernel/crash_core.c > +++ linux-x86/kernel/crash_core.c > @@ -31,7 +31,7 @@ static unsigned char *vmcoreinfo_data_sa > /* > * This function parses command lines in the format > * > - * crashkernel=ramsize-range:size[,...][@offset] > + * crashkernel=ramsize-range:size[,...][@offset][^order] > * > * The function returns 0 on success and -EINVAL on failure. > */ > @@ -41,6 +41,7 @@ static int __init parse_crashkernel_mem( > unsigned long long *crash_base) > { > char *cur = cmdline, *tmp; > + bool infinite_end = false; > > /* for each entry of the comma-separated list */ > do { > @@ -93,13 +94,21 @@ static int __init parse_crashkernel_mem( > /* match ? */ > if (system_ram >= start && system_ram < end) { > *crash_size = size; > + if (end == ULLONG_MAX) > + infinite_end = true; > break; > } > } while (*cur++ == ','); > > - if (*crash_size > 0) { > - while (*cur && *cur != ' ' && *cur != '@') > + if (*crash_size <= 0) > + goto out; > + > + while (*cur && *cur != ' ') { > + if (*cur != '@' && *cur != '^') { > cur++; > + continue; > + } > + > if (*cur == '@') { > cur++; > *crash_base = memparse(cur, &tmp); > @@ -107,10 +116,28 @@ static int __init parse_crashkernel_mem( > pr_warn("Memory value expected after '@'\n"); > return -EINVAL; > } > - } > + cur = tmp; > + } else if (*cur == '^' && infinite_end ) { > + unsigned long long shift, size; > + > + cur++; > + shift = memparse(cur, &tmp); > + if (cur == tmp) { > + pr_warn("Memory reservation scale order > expected after '^'\n"); > + return -EINVAL; > + } > + size = (system_ram - *crash_size) >> shift; > + size = *crash_size + roundup(size, 1ULL << 20); > + if (size < system_ram) > + *crash_size = size; > + cur = tmp; > + } else > + cur++; > } > > return 0; > +out: > + return -EINVAL; > } > > /* > --- linux-x86.orig/Documentation/admin-guide/kernel-parameters.txt > +++ linux-x86/Documentation/admin-guide/kernel-parameters.txt > @@ -680,12 +680,14 @@ > is selected automatically. Check > Documentation/kdump/kdump.txt for further details. > > - crashkernel=range1:size1[,range2:size2,...][@offset] > + crashkernel=range1:size1[,range2:size2,...][@offset][^order] > [KNL] Same as above, but depends on the memory > in the running system. The syntax of range is > - start-[end] where start and end are both > - a memory unit (amount[KMG]). See also > - Documentation/kdump/kdump.txt for an example. > + [start]-end where start and end are both > + a memory unit (amount[KMG]). In case the end of the > + range is infinity '^order' can be used to scale > + the size to size + (total_mem - start) >> 2^order > + See also Documentation/kdump/kdump.txt for an example. > > crashkernel=size[KMG],high > [KNL, x86_64] range could be above 4G. Allow kernel > --- linux-x86.orig/Documentation/kdump/kdump.txt > +++ linux-x86/Documentation/kdump/kdump.txt > @@ -267,19 +267,20 @@ been removed from the machine. > > The syntax is: > > - crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset] > + crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset][^order] > range=start-[end] > > For example: > > - crashkernel=512M-2G:64M,2G-:128M > + crashkernel=512M-2G:64M,2G-:128M^14 > > This would mean: > > 1) if the RAM is smaller than 512M, then don't reserve anything > (this is the "rescue" case) > 2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M > - 3) if the RAM size is larger than 2G, then reserve 128M > + 3) if the RAM size is larger than 2G, then reserve: > + 128M + (total_mem - 128M) >> 14 > > > > >
