todo: Investigate qemu caching modes.

1 files changed, 16 insertions, 0 deletions

diff --git a/TODO b/TODO
index a89d52e7..247f98a1 100644
--- a/TODO
+++ b/TODO
@@ -498,3 +498,19 @@ should.  There is a command line tool designed for scripts called
 this approach works, it doesn't solve the MBR problem, so likely we'd
 have to write a library for that (or perhaps go back to sfdisk but
 using a very abstracted interface over sfdisk).
+
+qemu caching
+------------
+
+(Suggested by Paolo Bonzini and Kevin Wolf)
+
+Measure the effect of cache=none, cache=directsync,
+cache=writethrough, cache=writeback.
+
+It's doubtful that using cache=none is useful, since it disables the
+host cache making read-heavy workloads slower (they rely entirely on
+the smaller appliance kernel's cache).  And in libguestfs we don't
+necessarily care about ongoing data integrity while writing, as long
+as data is reliably written out when g.sync or g.close return.  Also
+in libguestfs we effectively control the whole stack, so we can ensure
+write barriers happen when we want.