From 3ee48b6af49cf534ca2f481ecc484b156a41451d Mon Sep 17 00:00:00 2001 From: Cliff Wickman Date: Thu, 16 Sep 2010 11:44:02 -0500 Subject: [PATCH] mm, x86: Saving vmcore with non-lazy freeing of vmas 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 Cc: Andrew Morton Cc: kexec@lists.infradead.org Cc: LKML-Reference: Signed-off-by: Ingo Molnar --- arch/x86/include/asm/io.h | 1 + arch/x86/kernel/crash_dump_64.c | 1 + mm/vmalloc.c | 9 +++++++++ 3 files changed, 11 insertions(+) diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h index 30a3e9776123..6a45ec41ec26 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 bf43188ca654..994828899e09 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 6b8889da69a6..d8087f0db507 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -516,6 +516,15 @@ static atomic_t vmap_lazy_nr = ATOMIC_INIT(0); /* for per-CPU blocks */ 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. *