makedumpfile-1.5.1: Improve performance for cyclic mode.

[kumagai-atsushi@xxxxxxxxxxxxxxxxx (Atsushi Kumagai)]

On Thu, 6 Dec 2012 13:32:08 +0900
Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp> wrote:

> Hello,
> 
> makedumpfile version 1.5.1 is released.
> Your comments/patches are welcome.
> 
> Main new feature:
> o Support for snappy compression
>   This feature allows you to compress dump data by each page using snappy.
>   This feature is optional, the user has to prepare snappy library and
>   build binary with USESNAPPY=on to use it. 
> 
> o Introduce mem_map array logic
>   This is the new logic of excluding free pages. This logic excludes free 
>   pages by looking up mem_map array instead of free lists, and is expected
>   good performance for cyclic mode.
> 
>   This feature requires the values below but vmcore doesn't include them,
>   so the user has to prepare vmlinux or vmcoreinfo which includes them. 
>   When running on cyclic mode and the required values exist, mem_map array
>   logic is used. Otherwise, free list logic is used.
> 
>     kernel v2.6.38 to latest:
>       - OFFSET(page._mapcount)
>       - OFFSET(page.private)
>       - NUMBER(PG_slab)
>       - NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE)
> 
>     kernel v2.6.18 to v2.6.37:
>       - OFFSET(page.private)
>       - NUMBER(PG_buddy)
> 
>     kernel v2.6.15 to v2.6.17:
>       Not supported.
> 
>   Additionally, I posted the patch below to add the values above to the
>   upstream kernel:
> 
>     https://lkml.org/lkml/2012/11/21/90
> 
>   If you apply it to 1st kernel, you can use mem_map array logic without
>   vmlinux.

NOTE: The patch above is for latest kernel. So you need to fix it as
      below if your kernel version is between v2.6.18 and v2.6.37:

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 511151b..56583a4 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1490,7 +1490,6 @@ static int __init crash_save_vmcoreinfo_init(void)
	VMCOREINFO_OFFSET(page, flags);
	VMCOREINFO_OFFSET(page, _count);
	VMCOREINFO_OFFSET(page, mapping);
-	VMCOREINFO_OFFSET(page, _mapcount);
	VMCOREINFO_OFFSET(page, private);
	VMCOREINFO_OFFSET(page, lru);
	VMCOREINFO_OFFSET(pglist_data, node_zones);
@@ -1515,8 +1514,7 @@ static int __init crash_save_vmcoreinfo_init(void)
	VMCOREINFO_NUMBER(PG_lru);
	VMCOREINFO_NUMBER(PG_private);
	VMCOREINFO_NUMBER(PG_swapcache);
-	VMCOREINFO_NUMBER(PG_slab);
-	VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE);
+	VMCOREINFO_NUMBER(PG_buddy);

	arch_crash_save_vmcoreinfo();
	update_vmcoreinfo_note();


Thanks
Atsushi Kumagai