The patch titled
readahead: add look-ahead support to __do_page_cache_readahead()
has been removed from the -mm tree. Its filename was
readahead-add-look-ahead-support-to-__do_page_cache_readahead.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
Subject: readahead: add look-ahead support to __do_page_cache_readahead()
From: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Add look-ahead support to __do_page_cache_readahead().
It works by
- mark the Nth backwards page with PG_readahead,
(which instructs the page's first reader to invoke readahead)
- and only do the marking for newly allocated pages.
(to prevent blindly doing readahead on already cached pages)
Look-ahead is a technique to achieve I/O pipelining:
While the application is working through a chunk of cached pages,
the kernel reads-ahead the next chunk of pages _before_ time of need.
It effectively hides low level I/O latencies to high level
applications.
Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/readahead.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff -puN mm/readahead.c~readahead-add-look-ahead-support-to-__do_page_cache_readahead mm/readahead.c
--- a/mm/readahead.c~readahead-add-look-ahead-support-to-__do_page_cache_readahead
+++ a/mm/readahead.c
@@ -267,7 +267,8 @@ out:
*/
static int
__do_page_cache_readahead(struct address_space *mapping, struct file *filp,
- pgoff_t offset, unsigned long nr_to_read)
+ pgoff_t offset, unsigned long nr_to_read,
+ unsigned long lookahead_size)
{
struct inode *inode = mapping->host;
struct page *page;
@@ -280,7 +281,7 @@ __do_page_cache_readahead(struct address
if (isize == 0)
goto out;
- end_index = ((isize - 1) >> PAGE_CACHE_SHIFT);
+ end_index = ((isize - 1) >> PAGE_CACHE_SHIFT);
/*
* Preallocate as many pages as we will need.
@@ -303,6 +304,8 @@ __do_page_cache_readahead(struct address
break;
page->index = page_offset;
list_add(&page->lru, &page_pool);
+ if (page_idx == nr_to_read - lookahead_size)
+ SetPageReadahead(page);
ret++;
}
read_unlock_irq(&mapping->tree_lock);
@@ -339,7 +342,7 @@ int force_page_cache_readahead(struct ad
if (this_chunk > nr_to_read)
this_chunk = nr_to_read;
err = __do_page_cache_readahead(mapping, filp,
- offset, this_chunk);
+ offset, this_chunk, 0);
if (err < 0) {
ret = err;
break;
@@ -386,7 +389,7 @@ int do_page_cache_readahead(struct addre
if (bdi_read_congested(mapping->backing_dev_info))
return -1;
- return __do_page_cache_readahead(mapping, filp, offset, nr_to_read);
+ return __do_page_cache_readahead(mapping, filp, offset, nr_to_read, 0);
}
/*
@@ -406,7 +409,7 @@ blockable_page_cache_readahead(struct ad
if (!block && bdi_read_congested(mapping->backing_dev_info))
return 0;
- actual = __do_page_cache_readahead(mapping, filp, offset, nr_to_read);
+ actual = __do_page_cache_readahead(mapping, filp, offset, nr_to_read, 0);
return check_ra_success(ra, nr_to_read, actual);
}
@@ -451,7 +454,7 @@ static int make_ahead_window(struct addr
* @req_size: hint: total size of the read which the caller is performing in
* PAGE_CACHE_SIZE units
*
- * page_cache_readahead() is the main function. If performs the adaptive
+ * page_cache_readahead() is the main function. It performs the adaptive
* readahead window size management and submits the readahead I/O.
*
* Note that @filp is purely used for passing on to the ->readpage[s]()
_
Patches currently in -mm which might be from wfg@xxxxxxxxxxxxxxxx are
origin.patch
readahead-add-look-ahead-support-to-__do_page_cache_readahead.patch
readahead-insert-cond_resched-calls.patch
readahead-minmax_ra_pages.patch
readahead-events-accounting.patch
readahead-rescue_pages.patch
readahead-sysctl-parameters.patch
readahead-min-max-sizes.patch
readahead-state-based-method-aging-accounting.patch
readahead-state-based-method-routines.patch
readahead-state-based-method.patch
readahead-state-based-method-check-node-id.patch
readahead-state-based-method-decouple-readahead_ratio-from-growth_limit.patch
readahead-state-based-method-cancel-lookahead-gracefully.patch
readahead-context-based-method.patch
readahead-initial-method-guiding-sizes.patch
readahead-initial-method-thrashing-guard-size.patch
readahead-initial-method-user-recommended-size.patch
readahead-initial-method.patch
readahead-backward-prefetching-method.patch
readahead-thrashing-recovery-method.patch
readahead-thrashing-recovery-method-check-unbalanced-aging.patch
readahead-thrashing-recovery-method-refill-holes.patch
readahead-call-scheme.patch
readahead-call-scheme-cleanup.patch
readahead-call-scheme-catch-thrashing-on-lookahead-time.patch
readahead-call-scheme-doc-fixes-for-readahead.patch
readahead-laptop-mode.patch
readahead-loop-case.patch
readahead-nfsd-case.patch
readahead-remove-parameter-ra_max-from-thrashing_recovery_readahead.patch
readahead-remove-parameter-ra_max-from-adjust_rala.patch
readahead-state-based-method-protect-against-tiny-size.patch
readahead-rename-state_based_readahead-to-clock_based_readahead.patch
readahead-account-i-o-block-times-for-stock-readahead.patch
readahead-rescue_pages-updates.patch
readahead-remove-noaction-shrink-events.patch
readahead-remove-size-limit-on-read_ahead_kb.patch
readahead-remove-size-limit-of-max_sectors_kb-on-read_ahead_kb.patch
readahead-partial-sendfile-fix.patch
readahead-turn-on-by-default.patch
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