On Fri, 18 Apr 2014, Mel Gorman wrote: > The write_end handler is likely to call SetPageUptodate which is an atomic > operation so prefetch the line. > > Signed-off-by: Mel Gorman <mgorman@xxxxxxx> This one seems a little odd to me: it feels as if you're compensating for your mark_page_accessed() movement, but in too shmem-specific a way. I see write_ends do SetPageUptodate more often than I was expecting (with __block_commit_write() doing so even when PageUptodate already), but even so... Given that the write_end is likely to want to SetPageDirty, and sure to want to clear_bit_unlock(PG_locked, &page->flags), wouldn't it be better and less mysterious just to prefetchw(&page->flags) here unconditionally? (But I'm also afraid that this sets a precedent for an avalanche of dubious prefetchw patches all over.) Hugh > --- > mm/filemap.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/filemap.c b/mm/filemap.c > index c28f69c..40713da 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2551,6 +2551,9 @@ again: > copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); > flush_dcache_page(page); > > + if (!PageUptodate(page)) > + prefetchw(&page->flags); > + > status = a_ops->write_end(file, mapping, pos, bytes, copied, > page, fsdata); > if (unlikely(status < 0)) > -- > 1.8.4.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>