[Libguestfs] [PATCH 2/2] builder: pxzcat: Add further posix_fadvise hints.

[Richard W.M. Jones]

Setting POSIX_FADV_RANDOM makes no measurable difference, but at least
it's the right thing to do.

POSIX_FADV_WILLNEED makes no measurable difference either.

Changing POSIX_FADV_NOREUSE on the input file descriptor to
POSIX_FADV_DONTNEED slows things down by about 10%.
---
 builder/pxzcat-c.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/builder/pxzcat-c.c b/builder/pxzcat-c.c
index 44722bc..0a1c368 100644
--- a/builder/pxzcat-c.c
+++ b/builder/pxzcat-c.c
@@ -215,6 +215,9 @@ pxzcat (value filenamev, value outputfilev, unsigned nr_threads)
   }
 
   guestfs_int_fadvise_noreuse (fd);
+  guestfs_int_fadvise_random (fd);
+  guestfs_int_fadvise_random (ofd);
+  guestfs_int_fadvise_willneed (ofd);
 
   /* Iterate over blocks. */
   iter_blocks (idx, nr_threads, filenamev, fd, outputfilev, ofd);
-- 
2.7.4