Commit graph

2 commits

Author SHA1 Message Date
Mikulas Patocka
a66cc28f53 dm bufio: prefetch
This patch introduces a new function dm_bufio_prefetch. It prefetches
the specified range of blocks into dm-bufio cache without waiting
for i/o completion.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2012-03-28 18:41:29 +01:00
Mikulas Patocka
95d402f057 dm: add bufio
The dm-bufio interface allows you to do cached I/O on devices,
holding recently-read blocks in memory and performing delayed writes.

We don't use buffer cache or page cache already present in the kernel, because:
* we need to handle block sizes larger than a page
* we can't allocate memory to perform reads or we'd have deadlocks

Currently, when a cache is required, we limit its size to a fraction of
available memory.  Usage can be viewed and changed in
/sys/module/dm_bufio/parameters/ .

The first user is thin provisioning, but more dm users are planned.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2011-10-31 20:19:09 +00:00