On Mon, 22 Jul 2019 16:13:37 -0400 Johannes Weiner <[email protected]> wrote:
> psi tracks the time tasks wait for refaulting pages to become > uptodate, but it does not track the time spent submitting the IO. The > submission part can be significant if backing storage is contended or > when cgroup throttling (io.latency) is in effect - a lot of time is > spent in submit_bio(). In that case, we underreport memory pressure. It's a somewhat broad patch. How significant is this problem in the real world? Can we be confident that the end-user benefit is worth the code changes? > Annotate the submit_bio() paths (or the indirection through readpage) > for refaults and swapin to get proper psi coverage of delays there. > > Signed-off-by: Johannes Weiner <[email protected]> > --- > fs/btrfs/extent_io.c | 14 ++++++++++++-- > fs/ext4/readpage.c | 9 +++++++++ > fs/f2fs/data.c | 8 ++++++++ > fs/mpage.c | 9 +++++++++ > mm/filemap.c | 20 ++++++++++++++++++++ > mm/page_io.c | 11 ++++++++--- > mm/readahead.c | 24 +++++++++++++++++++++++- We touch three filesystems. Why these three? Are all other filesystems OK or will they need work as well? > ... > > --- a/mm/filemap.c > +++ b/mm/filemap.c > > ... > > @@ -2753,11 +2763,14 @@ static struct page *do_read_cache_page(struct > address_space *mapping, > void *data, > gfp_t gfp) > { > + bool refault = false; > struct page *page; > int err; > repeat: > page = find_get_page(mapping, index); > if (!page) { > + unsigned long pflags; > + That was a bit odd. This? --- a/mm/filemap.c~psi-annotate-refault-stalls-from-io-submission-fix +++ a/mm/filemap.c @@ -2815,12 +2815,12 @@ static struct page *do_read_cache_page(s void *data, gfp_t gfp) { - bool refault = false; struct page *page; int err; repeat: page = find_get_page(mapping, index); if (!page) { + bool refault = false; unsigned long pflags; page = __page_cache_alloc(gfp); _
