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authorCliff Wickman <cpw@sgi.com>2010-09-16 18:44:02 +0200
committerIngo Molnar <mingo@elte.hu>2010-09-17 09:11:56 +0200
commit3ee48b6af49cf534ca2f481ecc484b156a41451d (patch)
treece55b9d5831a39ff75297c9fbfa8fa3471c99a3d /mm
parentx86, kdump: Change copy_oldmem_page() to use cached addressing (diff)
downloadlinux-3ee48b6af49cf534ca2f481ecc484b156a41451d.tar.xz
linux-3ee48b6af49cf534ca2f481ecc484b156a41451d.zip
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 <cpw@sgi.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: kexec@lists.infradead.org Cc: <stable@kernel.org> LKML-Reference: <E1OwHZ4-0005WK-Tw@eag09.americas.sgi.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'mm')
-rw-r--r--mm/vmalloc.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 6b8889da69a6..d8087f0db507 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -517,6 +517,15 @@ 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.