The patch titled
Subject: mm: fadvise: document the fadvise(FADV_DONTNEED) behaviour for partial pages
has been removed from the -mm tree. Its filename was
mm-fadvise-document-the-fadvisefadv_dontneed-behaviour-for-partial-pages.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxx>
Subject: mm: fadvise: document the fadvise(FADV_DONTNEED) behaviour for partial pages
A random seek IO benchmark appeared to regress because of a change to
readahead but the real problem was the benchmark. To ensure the IO
request accesssed disk, it used fadvise(FADV_DONTNEED) on a block boundary
(512K) but the hint is ignored by the kernel. This is correct but not
necessarily obvious behaviour. As much as I dislike comment patches, the
explanation for this behaviour predates current git history. Clarify why
it behaves like this in case someone "fixes" fadvise or readahead for the
wrong reasons.
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/fadvise.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff -puN mm/fadvise.c~mm-fadvise-document-the-fadvisefadv_dontneed-behaviour-for-partial-pages mm/fadvise.c
--- a/mm/fadvise.c~mm-fadvise-document-the-fadvisefadv_dontneed-behaviour-for-partial-pages
+++ a/mm/fadvise.c
@@ -117,7 +117,11 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, l
__filemap_fdatawrite_range(mapping, offset, endbyte,
WB_SYNC_NONE);
- /* First and last FULL page! */
+ /*
+ * First and last FULL page! Partial pages are deliberately
+ * preserved on the expectation that it is better to preserve
+ * needed memory than to discard unneeded memory.
+ */
start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
end_index = (endbyte >> PAGE_CACHE_SHIFT);
_
Patches currently in -mm which might be from mgorman@xxxxxxx are
origin.patch
mm-introduce-do_shared_fault-and-drop-do_fault-fix-fix.patch
do_shared_fault-check-that-mmap_sem-is-held.patch
linux-next.patch
lib-show_mem-this-patch-adds-cma-reserved-infromation.patch
lib-show_mem-this-patch-adds-cma-reserved-infromation-fix.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
