On 01/27/2022 11:53 PM, Petr Tesařík wrote:
Hi Tiezhu Yang,
I'm afraid the whole concept is broken by design. See below.
Dne 27. 01. 22 v 10:31 Tiezhu Yang napsal(a):
Set the reserved memory automatically for the crash kernel based on
architecture.
Most code of this patch come from:
https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-8/-/tree/c8s
And that's the problem, I think. The solution might be good for this
specific OS, but not for others.
Hi Petr,
Thank you for your reply.
This is a RFC patch, the initial aim of this patch is to discuss what is
the proper way to support crashkernel=auto.
A moment ago, I find the following patch, it is more flexible, but it is
not merged into the upstream kernel now.
kernel/crash_core: Add crashkernel=auto for vmcore creation
https://lore.kernel.org/lkml/20210223174153.72802-1-saeed.mirzamohammadi@xxxxxxxxxx/
[...]
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 256cf6d..32c51e2 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -252,6 +252,26 @@ static int __init __parse_crashkernel(char *cmdline,
if (suffix)
return parse_crashkernel_suffix(ck_cmdline, crash_size,
suffix);
+
+ if (strncmp(ck_cmdline, "auto", 4) == 0) {
+#if defined(CONFIG_X86_64) || defined(CONFIG_S390)
+ ck_cmdline = "1G-4G:160M,4G-64G:192M,64G-1T:256M,1T-:512M";
+#elif defined(CONFIG_ARM64)
+ ck_cmdline = "2G-:448M";
+#elif defined(CONFIG_PPC64)
+ char *fadump_cmdline;
+
+ fadump_cmdline = get_last_crashkernel(cmdline, "fadump=", NULL);
+ fadump_cmdline = fadump_cmdline ?
+ fadump_cmdline + strlen("fadump=") : NULL;
+ if (!fadump_cmdline || (strncmp(fadump_cmdline, "off", 3) == 0))
+ ck_cmdline =
"2G-4G:384M,4G-16G:512M,16G-64G:1G,64G-128G:2G,128G-:4G";
+ else
+ ck_cmdline =
"4G-16G:768M,16G-64G:1G,64G-128G:2G,128G-1T:4G,1T-2T:6G,2T-4T:12G,4T-8T:20G,8T-16T:36G,16T-32T:64G,32T-64T:128G,64T-:180G";
+#endif
+ pr_info("Using crashkernel=auto, the size chosen is a best
effort estimation.\n");
+ }
+
How did you even arrive at the above numbers?
Memory requirements for kdump:
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/managing_monitoring_and_updating_the_kernel/supported-kdump-configurations-and-targets_managing-monitoring-and-updating-the-kernel#memory-requirements-for-kdump_supported-kdump-configurations-and-targets
I've done some research on
this topic recently (ie. during the last 7 years or so). My x86_64
system with 8G RAM running openSUSE Leap 15.3 seems needs 188M for
saving to the local disk, and 203M to save over the network (using
SFTP). My PPC64 LPAR with 16G RAM running latest Beta of SLES 15 SP4
needs 587M, i.e. with the above numbers it may run out of memory while
saving the dump.
Since this is not the first time, I'm trying to explain things, I've
written a blog post now:
https://sigillatum.tesarici.cz/2022-01-27-whats-wrong-with-crashkernel-auto.html
Thank you, this is useful.
Thanks,
Tiezhu
HTH
Petr Tesarik
