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| author | Cliff Wickman <cpw@sgi.com> | 2010-09-16 11:44:02 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-11-22 10:59:47 -0800 |
| commit | ff7d23175ecbff5666f7a9f26dfe1f4334e04377 (patch) | |
| tree | 40f94039ba638de7ac8243cbdd5a3f5edaf9af5d /mm | |
| parent | db11393d79684afc15b3d3d52a1664171180c350 (diff) | |
| download | lwn-ff7d23175ecbff5666f7a9f26dfe1f4334e04377.tar.gz lwn-ff7d23175ecbff5666f7a9f26dfe1f4334e04377.zip | |
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: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/vmalloc.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index ae007462b7f6..20a402ce7bd2 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. |