Record the readahead pattern in ra_flags and extend the ra_submit()
parameters, to be used by the next readahead tracing/stats patches.
7 patterns are defined:
pattern readahead for
-----------------------------------------------------------
RA_PATTERN_INITIAL start-of-file read
RA_PATTERN_SUBSEQUENT trivial sequential read
RA_PATTERN_CONTEXT interleaved sequential read
RA_PATTERN_OVERSIZE oversize read
RA_PATTERN_MMAP_AROUND mmap fault
RA_PATTERN_FADVISE posix_fadvise()
RA_PATTERN_RANDOM random read
Note that random reads will be recorded in file_ra_state now.
This won't deteriorate cache bouncing because the ra->prev_pos update
in do_generic_file_read() already pollutes the data cache, and
filemap_fault() will stop calling into us after MMAP_LOTSAMISS.
CC: Ingo Molnar <mingo@xxxxxxx>
CC: Jens Axboe <jens.axboe@xxxxxxxxxx>
CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
include/linux/fs.h | 33 +++++++++++++++++++++++++++++++++
include/linux/mm.h | 4 +++-
mm/filemap.c | 9 +++++++--
mm/readahead.c | 30 +++++++++++++++++++++++-------
4 files changed, 66 insertions(+), 10 deletions(-)
--- linux-next.orig/include/linux/fs.h 2011-11-20 20:10:48.000000000 +0800
+++ linux-next/include/linux/fs.h 2011-11-20 20:18:29.000000000 +0800
@@ -951,6 +951,39 @@ struct file_ra_state {
/* ra_flags bits */
#define READAHEAD_MMAP_MISS 0x000003ff /* cache misses for mmap access */
+#define READAHEAD_MMAP 0x00010000
+
+#define READAHEAD_PATTERN_SHIFT 28
+#define READAHEAD_PATTERN 0xf0000000
+
+/*
+ * Which policy makes decision to do the current read-ahead IO?
+ */
+enum readahead_pattern {
+ RA_PATTERN_INITIAL,
+ RA_PATTERN_SUBSEQUENT,
+ RA_PATTERN_CONTEXT,
+ RA_PATTERN_MMAP_AROUND,
+ RA_PATTERN_FADVISE,
+ RA_PATTERN_OVERSIZE,
+ RA_PATTERN_RANDOM,
+ RA_PATTERN_ALL, /* for summary stats */
+ RA_PATTERN_MAX
+};
+
+static inline unsigned int ra_pattern(unsigned int ra_flags)
+{
+ unsigned int pattern = ra_flags >> READAHEAD_PATTERN_SHIFT;
+
+ return min_t(unsigned int, pattern, RA_PATTERN_ALL);
+}
+
+static inline void ra_set_pattern(struct file_ra_state *ra,
+ unsigned int pattern)
+{
+ ra->ra_flags = (ra->ra_flags & ~READAHEAD_PATTERN) |
+ (pattern << READAHEAD_PATTERN_SHIFT);
+}
/*
* Don't do ra_flags++ directly to avoid possible overflow:
--- linux-next.orig/mm/readahead.c 2011-11-20 20:10:48.000000000 +0800
+++ linux-next/mm/readahead.c 2011-11-20 20:18:14.000000000 +0800
@@ -268,13 +268,17 @@ unsigned long max_sane_readahead(unsigne
* Submit IO for the read-ahead request in file_ra_state.
*/
unsigned long ra_submit(struct file_ra_state *ra,
- struct address_space *mapping, struct file *filp)
+ struct address_space *mapping,
+ struct file *filp,
+ pgoff_t offset,
+ unsigned long req_size)
{
int actual;
actual = __do_page_cache_readahead(mapping, filp,
ra->start, ra->size, ra->async_size);
+ ra->ra_flags &= ~READAHEAD_MMAP;
return actual;
}
@@ -401,6 +405,7 @@ static int try_context_readahead(struct
if (size >= offset)
size *= 2;
+ ra_set_pattern(ra, RA_PATTERN_CONTEXT);
ra->start = offset;
ra->size = get_init_ra_size(size + req_size, max);
ra->async_size = ra->size;
@@ -422,8 +427,10 @@ ondemand_readahead(struct address_space
/*
* start of file
*/
- if (!offset)
+ if (!offset) {
+ ra_set_pattern(ra, RA_PATTERN_INITIAL);
goto initial_readahead;
+ }
/*
* It's the expected callback offset, assume sequential access.
@@ -431,6 +438,7 @@ ondemand_readahead(struct address_space
*/
if ((offset == (ra->start + ra->size - ra->async_size) ||
offset == (ra->start + ra->size))) {
+ ra_set_pattern(ra, RA_PATTERN_SUBSEQUENT);
ra->start += ra->size;
ra->size = get_next_ra_size(ra, max);
ra->async_size = ra->size;
@@ -453,6 +461,7 @@ ondemand_readahead(struct address_space
if (!start || start - offset > max)
return 0;
+ ra_set_pattern(ra, RA_PATTERN_CONTEXT);
ra->start = start;
ra->size = start - offset; /* old async_size */
ra->size += req_size;
@@ -464,14 +473,18 @@ ondemand_readahead(struct address_space
/*
* oversize read
*/
- if (req_size > max)
+ if (req_size > max) {
+ ra_set_pattern(ra, RA_PATTERN_OVERSIZE);
goto initial_readahead;
+ }
/*
* sequential cache miss
*/
- if (offset - (ra->prev_pos >> PAGE_CACHE_SHIFT) <= 1UL)
+ if (offset - (ra->prev_pos >> PAGE_CACHE_SHIFT) <= 1UL) {
+ ra_set_pattern(ra, RA_PATTERN_INITIAL);
goto initial_readahead;
+ }
/*
* Query the page cache and look for the traces(cached history pages)
@@ -482,9 +495,12 @@ ondemand_readahead(struct address_space
/*
* standalone, small random read
- * Read as is, and do not pollute the readahead state.
*/
- return __do_page_cache_readahead(mapping, filp, offset, req_size, 0);
+ ra_set_pattern(ra, RA_PATTERN_RANDOM);
+ ra->start = offset;
+ ra->size = req_size;
+ ra->async_size = 0;
+ goto readit;
initial_readahead:
ra->start = offset;
@@ -502,7 +518,7 @@ readit:
ra->size += ra->async_size;
}
- return ra_submit(ra, mapping, filp);
+ return ra_submit(ra, mapping, filp, offset, req_size);
}
/**
--- linux-next.orig/include/linux/mm.h 2011-11-20 20:10:48.000000000 +0800
+++ linux-next/include/linux/mm.h 2011-11-20 20:10:49.000000000 +0800
@@ -1456,7 +1456,9 @@ void page_cache_async_readahead(struct a
unsigned long max_sane_readahead(unsigned long nr);
unsigned long ra_submit(struct file_ra_state *ra,
struct address_space *mapping,
- struct file *filp);
+ struct file *filp,
+ pgoff_t offset,
+ unsigned long req_size);
/* Generic expand stack which grows the stack according to GROWS{UP,DOWN} */
extern int expand_stack(struct vm_area_struct *vma, unsigned long address);
--- linux-next.orig/mm/filemap.c 2011-11-20 20:10:48.000000000 +0800
+++ linux-next/mm/filemap.c 2011-11-20 20:10:49.000000000 +0800
@@ -1592,6 +1592,7 @@ static void do_sync_mmap_readahead(struc
return;
if (VM_SequentialReadHint(vma)) {
+ ra->ra_flags |= READAHEAD_MMAP;
page_cache_sync_readahead(mapping, ra, file, offset,
ra->ra_pages);
return;
@@ -1607,11 +1608,13 @@ static void do_sync_mmap_readahead(struc
/*
* mmap read-around
*/
+ ra->ra_flags |= READAHEAD_MMAP;
+ ra_set_pattern(ra, RA_PATTERN_MMAP_AROUND);
ra_pages = max_sane_readahead(ra->ra_pages);
ra->start = max_t(long, 0, offset - ra_pages / 2);
ra->size = ra_pages;
ra->async_size = ra_pages / 4;
- ra_submit(ra, mapping, file);
+ ra_submit(ra, mapping, file, offset, 1);
}
/*
@@ -1630,9 +1633,11 @@ static void do_async_mmap_readahead(stru
if (VM_RandomReadHint(vma))
return;
ra_mmap_miss_dec(ra);
- if (PageReadahead(page))
+ if (PageReadahead(page)) {
+ ra->ra_flags |= READAHEAD_MMAP;
page_cache_async_readahead(mapping, ra, file,
page, offset, ra->ra_pages);
+ }
}
/**
--
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