Hi Baoquan, On 10/24/17 at 02:00pm, Baoquan He wrote: > 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.
But this is better than embed policy in kernel.. RHEL takes a crashkernel=auto which do the scaling. Leaving user to determine the scaling ratio is the better way. OTOH, this is an improvement to current crashkernel=range:size which can not scale the size before. > > > > > 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 > > > > > > > > > > Thanks Dave
