The DM_BUFIO_HASH_BITS is defined as 20, any plan to make it flexible?

Hi NeilBrown,

See drivers/md/dm-bufio.c as below:

   50 /*
   51  * Buffer hash
   52  */
   53 #define DM_BUFIO_HASH_BITS      20
   54 #define DM_BUFIO_HASH(block) \
   55         ((((block) >> DM_BUFIO_HASH_BITS) ^ (block)) & \
   56          ((1 << DM_BUFIO_HASH_BITS) - 1))

"drivers/md/dm-bufio.c" 1854L, 45375C

DM_BUFIO_HASH_BITS was defined as 20 and it maybe not fit for some use case with limited resources. Do we have any plan to make it more flexible? Like module parameter or something else?

Quoted 13 lines · On Tue, 2 Dec 2014 16:32:14 +0800 zhangxiao <[email protected]> wrote:

Hi NeilBrown,

See drivers/md/dm-bufio.c as below:

    50 /*
    51  * Buffer hash
    52  */
    53 #define DM_BUFIO_HASH_BITS      20
    54 #define DM_BUFIO_HASH(block) \
    55         ((((block) >> DM_BUFIO_HASH_BITS) ^ (block)) & \
    56          ((1 << DM_BUFIO_HASH_BITS) - 1))

"drivers/md/dm-bufio.c" 1854L, 45375C

Quoted 4 lines

DM_BUFIO_HASH_BITS was defined as 20 and it maybe not fit for some use case with limited resources. Do we have any plan to make it more flexible? Like module parameter or something else?

Thanks, but this question should be address to:

DEVICE-MAPPER (LVM)
M: Alasdair Kergon <[email protected]>
M: Mike Snitzer <[email protected]>
M: [email protected]
L: [email protected]
W: http://sources.redhat.com/dm
Q: http://patchwork.kernel.org/project/dm-devel/list/
T: git git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git
T: quilt http://people.redhat.com/agk/patches/linux/editing/
S: Maintained
F: Documentation/device-mapper/
F: drivers/md/dm*
F: drivers/md/persistent-data/
F: include/linux/device-mapper.h
F: include/linux/dm-*.h
F: include/uapi/linux/dm-*.h

NeilBrown