| From 9878732e77937741bfa80598c69ef039c43945b7 Mon Sep 17 00:00:00 2001 |
| From: Cliff Wickman <cpw@sgi.com> |
| Date: Thu, 16 Sep 2010 11:44:02 -0500 |
| Subject: [PATCH] mm, x86: Saving vmcore with non-lazy freeing of vmas |
| |
| commit 3ee48b6af49cf534ca2f481ecc484b156a41451d upstream. |
| |
| During the reading of /proc/vmcore the kernel is doing |
| ioremap()/iounmap() repeatedly. And the buildup of un-flushed |
| vm_area_struct's is causing a great deal of overhead. (rb_next() |
| is chewing up most of that time). |
| |
| This solution is to provide function set_iounmap_nonlazy(). It |
| causes a subsequent call to iounmap() to immediately purge the |
| vma area (with try_purge_vmap_area_lazy()). |
| |
| With this patch we have seen the time for writing a 250MB |
| compressed dump drop from 71 seconds to 44 seconds. |
| |
| Signed-off-by: Cliff Wickman <cpw@sgi.com> |
| Cc: Andrew Morton <akpm@linux-foundation.org> |
| Cc: kexec@lists.infradead.org |
| LKML-Reference: <E1OwHZ4-0005WK-Tw@eag09.americas.sgi.com> |
| Signed-off-by: Ingo Molnar <mingo@elte.hu> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| --- |
| arch/x86/include/asm/io.h | 1 + |
| arch/x86/kernel/crash_dump_64.c | 1 + |
| mm/vmalloc.c | 9 +++++++++ |
| 3 files changed, 11 insertions(+), 0 deletions(-) |
| |
| diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h |
| index 30a3e97..6a45ec4 100644 |
| --- a/arch/x86/include/asm/io.h |
| +++ b/arch/x86/include/asm/io.h |
| @@ -206,6 +206,7 @@ static inline void __iomem *ioremap(resource_size_t offset, unsigned long size) |
| |
| extern void iounmap(volatile void __iomem *addr); |
| |
| +extern void set_iounmap_nonlazy(void); |
| |
| #ifdef __KERNEL__ |
| |
| diff --git a/arch/x86/kernel/crash_dump_64.c b/arch/x86/kernel/crash_dump_64.c |
| index 045b36c..ce96a6b 100644 |
| --- a/arch/x86/kernel/crash_dump_64.c |
| +++ b/arch/x86/kernel/crash_dump_64.c |
| @@ -46,6 +46,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf, |
| } else |
| memcpy(buf, vaddr + offset, csize); |
| |
| + set_iounmap_nonlazy(); |
| iounmap(vaddr); |
| return csize; |
| } |
| diff --git a/mm/vmalloc.c b/mm/vmalloc.c |
| index ae00746..20a402c 100644 |
| --- a/mm/vmalloc.c |
| +++ b/mm/vmalloc.c |
| @@ -513,6 +513,15 @@ static atomic_t vmap_lazy_nr = ATOMIC_INIT(0); |
| static void purge_fragmented_blocks_allcpus(void); |
| |
| /* |
| + * called before a call to iounmap() if the caller wants vm_area_struct's |
| + * immediately freed. |
| + */ |
| +void set_iounmap_nonlazy(void) |
| +{ |
| + atomic_set(&vmap_lazy_nr, lazy_max_pages()+1); |
| +} |
| + |
| +/* |
| * Purges all lazily-freed vmap areas. |
| * |
| * If sync is 0 then don't purge if there is already a purge in progress. |
| -- |
| 1.7.0.4 |
| |