tree 086688168650fe491deae0da957307c337bc26c5
parent 77000bc43da17d5d6bc4ebfaf44d52d43bb69492
author Eric Dumazet <edumazet@google.com> 1551206559 -0800
committer Al Viro <viro@zeniv.linux.org.uk> 1551207920 -0500

iov_iter: optimize page_copy_sane()

Avoid cache line miss dereferencing struct page if we can.

page_copy_sane() mostly deals with order-0 pages.

Extra cache line miss is visible on TCP recvmsg() calls dealing
with GRO packets (typically 45 page frags are attached to one skb).

Bringing the 45 struct pages into cpu cache while copying the data
is not free, since the freeing of the skb (and associated
page frags put_page()) can happen after cache lines have been evicted.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>