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