linux.git/mm/readahead.c, branch v2.6.26

mm: bdi: export BDI attributes in sysfs

2008-04-30T15:29:49+00:00

Provide a place in sysfs (/sys/class/bdi) for the backing_dev_info object.
This allows us to see and set the various BDI specific variables.

In particular this properly exposes the read-ahead window for all relevant
users and /sys/block//queue/read_ahead_kb should be deprecated.

With patient help from Kay Sievers and Greg KH

[mszeredi@suse.cz]

 - split off NFS and FUSE changes into separate patches
 - document new sysfs attributes under Documentation/ABI
 - do bdi_class_init as a core_initcall, otherwise the "default" BDI
   won't be initialized
 - remove bdi_init_fmt macro, it's not used very much

[akpm@linux-foundation.org: fix ia64 warning]
Signed-off-by: Peter Zijlstra 
Cc: Kay Sievers 
Acked-by: Greg KH 
Cc: Trond Myklebust 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/readahead: fix kernel-doc notation

2008-03-20T01:53:37+00:00

Fix kernel-doc notation in mm/readahead.c.

Change ":" to ";" so that it doesn't get treated as a doc section heading.
Move the comment block ending "*/" to a line by itself so that the text on
that last line is not lost (dropped).

Signed-off-by: Randy Dunlap 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: bdi init hooks

2007-10-17T15:42:45+00:00

provide BDI constructor/destructor hooks

[akpm@linux-foundation.org: compile fix]
Signed-off-by: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: buffered write cleanup

2007-10-16T16:42:54+00:00

Quite a bit of code is used in maintaining these "cached pages" that are
probably pretty unlikely to get used. It would require a narrow race where
the page is inserted concurrently while this process is allocating a page
in order to create the spare page. Then a multi-page write into an uncached
part of the file, to make use of it.

Next, the buffered write path (and others) uses its own LRU pagevec when it
should be just using the per-CPU LRU pagevec (which will cut down on both data
and code size cacheline footprint). Also, these private LRU pagevecs are
emptied after just a very short time, in contrast with the per-CPU pagevecs
that are persistent. Net result: 7.3 times fewer lru_lock acquisitions required
to add the pages to pagecache for a bulk write (in 4K chunks).

[this gets rid of some cond_resched() calls in readahead.c and mpage.c due
 to clashes in -mm. What put them there, and why? ]

Signed-off-by: Nick Piggin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: use lockless radix-tree probe

2007-10-16T16:42:53+00:00

Probing pages and radix_tree_tagged are lockless operations with the lockless
radix-tree.  Convert these users to RCU locking rather than using tree_lock.

Signed-off-by: Nick Piggin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

readahead: remove several readahead macros

2007-10-16T16:42:52+00:00

Remove VM_MAX_CACHE_HIT, MAX_RA_PAGES and MIN_RA_PAGES.

Signed-off-by: Fengguang Wu 
Cc: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

readahead: basic support of interleaved reads

2007-10-16T16:42:52+00:00

This is a simplified version of the pagecache context based readahead.  It
handles the case of multiple threads reading on the same fd and invalidating
each others' readahead state.  It does the trick by scanning the pagecache and
recovering the current read stream's readahead status.

The algorithm works in a opportunistic way, in that it does not try to detect
interleaved reads _actively_, which requires a probe into the page cache
(which means a little more overhead for random reads).  It only tries to
handle a previously started sequential readahead whose state was overwritten
by another concurrent stream, and it can do this job pretty well.

Negative and positive examples(or what you can expect from it):

1) it cannot detect and serve perfect request-by-request interleaved reads
   right:
	time	stream 1  stream 2
	0 	1
	1 	          1001
	2 	2
	3 	          1002
	4 	3
	5 	          1003
	6 	4
	7 	          1004
	8 	5
	9	          1005

Here no single readahead will be carried out.

2) However, if it's two concurrent reads by two threads, the chance of the
   initial sequential readahead be started is huge. Once the first sequential
   readahead is started for a stream, this patch will ensure that the readahead
   window continues to rampup and won't be disturbed by other streams.

	time	stream 1  stream 2
	0 	1
	1 	2
	2 	          1001
	3 	3
	4 	          1002
	5 	          1003
	6 	4
	7 	5
	8 	          1004
	9 	6
	10	          1005
	11	7
	12	          1006
	13	          1007

Here stream 1 will start a readahead at page 2, and stream 2 will start its
first readahead at page 1003.  From then on the two streams will be served
right.

Cc: Rusty Russell 
Signed-off-by: Fengguang Wu 
Cc: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

readahead: combine file_ra_state.prev_index/prev_offset into prev_pos

2007-10-16T16:42:52+00:00

Combine the file_ra_state members
				unsigned long prev_index
				unsigned int prev_offset
into
				loff_t prev_pos

It is more consistent and better supports huge files.

Thanks to Peter for the nice proposal!

[akpm@linux-foundation.org: fix shift overflow]
Cc: Peter Zijlstra 
Signed-off-by: Fengguang Wu 
Cc: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

readahead: compacting file_ra_state

2007-10-16T16:42:52+00:00

Use 'unsigned int' instead of 'unsigned long' for readahead sizes.

This helps reduce memory consumption on 64bit CPU when a lot of files are
opened.

CC: Andi Kleen 
Signed-off-by: Fengguang Wu 
Cc: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Fix warnings with !CONFIG_BLOCK

2007-10-10T07:25:57+00:00

Hide everything in blkdev.h with CONFIG_BLOCK isn't set, and fixup
the (few) files that fail to build because they were relying on blkdev.h
pulling in extra includes for them.

Signed-off-by: Jens Axboe