diff options
| author | Jens Axboe <axboe@fb.com> | 2016-12-12 16:43:26 -0800 |
|---|---|---|
| committer | Alistair Strachan <astrachan@google.com> | 2019-01-23 21:46:19 +0000 |
| commit | e7c8b35e486775af65636a2a2b2766c3def9a8e8 (patch) | |
| tree | a3ab7ed7a2c106aff08ec23df5c541d9900fd05c /include/linux/backing-dev-defs.h | |
| parent | 24189101975d0efe8d75557f47f1406faa4dffaa (diff) | |
UPSTREAM: mm: don't cap request size based on read-ahead setting
We ran into a funky issue, where someone doing 256K buffered reads saw
128K requests at the device level. Turns out it is read-ahead capping
the request size, since we use 128K as the default setting. This
doesn't make a lot of sense - if someone is issuing 256K reads, they
should see 256K reads, regardless of the read-ahead setting, if the
underlying device can support a 256K read in a single command.
This patch introduces a bdi hint, io_pages. This is the soft max IO
size for the lower level, I've hooked it up to the bdev settings here.
Read-ahead is modified to issue the maximum of the user request size,
and the read-ahead max size, but capped to the max request size on the
device side. The latter is done to avoid reading ahead too much, if the
application asks for a huge read. With this patch, the kernel behaves
like the application expects.
Change-Id: Ibe52ffac7a6e1ac86ed0c6a59a0f7a32d651ee5f
Link: http://lkml.kernel.org/r/1479498073-8657-1-git-send-email-axboe@fb.com
Signed-off-by: Jens Axboe <axboe@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
Diffstat (limited to 'include/linux/backing-dev-defs.h')
| -rw-r--r-- | include/linux/backing-dev-defs.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index a307c37c2e6c..782d62673292 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -136,6 +136,7 @@ struct bdi_writeback { struct backing_dev_info { struct list_head bdi_list; unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */ + unsigned long io_pages; /* max allowed IO size */ unsigned int capabilities; /* Device capabilities */ congested_fn *congested_fn; /* Function pointer if device is md/dm */ void *congested_data; /* Pointer to aux data for congested func */ |