Hi
Here I'm sending the GFP_NOIO message patch.
I tried the approach with double scan of the message and no reallocation,
but it performs 5% worse on dm-switch table loading. So I stayed with the
current approach that does single scan and argv reallocation.
Mikulas
---
dm: allocate buffer for messages with small number of arguments with GFP_NOIO
dm-mpath and dm-thin must process messages even if some device is
suspended, so we allocate argv buffer with GFP_NOIO. These messages have a
small fixed number of arguments.
On the other hand, dm-switch needs to process bulk data using messages and
excessive use of GFP_NOIO could cause trouble.
The patch also lowers the default number of arguments from 64 to 8, so
that there is smaller load on GFP_NOIO allocations.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: stable@xxxxxxxxxx
---
drivers/md/dm-table.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
Index: linux-3.11.2-fast/drivers/md/dm-table.c
===================================================================
--- linux-3.11.2-fast.orig/drivers/md/dm-table.c 2013-09-30 19:39:40.000000000 +0200
+++ linux-3.11.2-fast/drivers/md/dm-table.c 2013-09-30 19:40:44.000000000 +0200
@@ -545,14 +545,28 @@ static int adjoin(struct dm_table *table
/*
* Used to dynamically allocate the arg array.
+ *
+ * We do first allocation with GFP_NOIO because dm-mpath and dm-thin must
+ * process messages even if some device is suspended. These messages have a
+ * small fixed number of arguments.
+ *
+ * On the other hand, dm-switch needs to process bulk data using messages and
+ * excessive use of GFP_NOIO could cause trouble.
*/
static char **realloc_argv(unsigned *array_size, char **old_argv)
{
char **argv;
unsigned new_size;
+ gfp_t gfp;
- new_size = *array_size ? *array_size * 2 : 64;
- argv = kmalloc(new_size * sizeof(*argv), GFP_KERNEL);
+ if (*array_size) {
+ new_size = *array_size * 2;
+ gfp = GFP_KERNEL;
+ } else {
+ new_size = 8;
+ gfp = GFP_NOIO;
+ }
+ argv = kmalloc(new_size * sizeof(*argv), gfp);
if (argv) {
memcpy(argv, old_argv, *array_size * sizeof(*argv));
*array_size = new_size;
--
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