flamegraphs: Move demo of flamegraph earlier

[libguestfs-talks.git] / 2019-kvm-forum / 4500-new-qemu-flag.html

diff --git a/2019-kvm-forum/4500-new-qemu-flag.html b/2019-kvm-forum/4500-new-qemu-flag.html
index c3e4142..ea729bb 100644 (file)
--- a/2019-kvm-forum/4500-new-qemu-flag.html
+++ b/2019-kvm-forum/4500-new-qemu-flag.html
@@ -5,19 +5,17 @@
 <h1>The fix: raise the victory flag</h1>
 
 <p>
-  Filler text - need a graphic here showing multiple combinations:
+  QEMU 4.0 added <code>BDRV_REQ_NO_FALLBACK</code> to detect if
+  zeroing is fast, and automatically utilizes it during 'qemu-img
+  convert':
+  <ul>
+    <li>No support for flag: avoid pre-zeroing
+    <li>Flag supported and succeeds (for O(1) implementation):
+      pre-zeroing is a win
+    <li>Flag supported but fails (for O(n) implementation): no penalty
+      from pre-zeroing
+  </ul>
 
-  <br>[WZ] = WRITE_ZEROES, normal
-  <br>[FZ+] = WRITE_ZEROES, successful with FAST_ZERO flag
-  <br>[FZ-] = WRITE_ZEROES, fails with FAST_ZERO flag
-  <br>[W...] = WRITE for data
-
-<pre>
-                  O(1) server             O(n) server
-pre-patch         [W...][WZ][W...][WZ]    [W...][WZ..][W...][WZ..]
-
-with fast zero    [FZ+][W...][W...]       [FZ-][W...][WZ..][W...][WZ..]
-                  (faster)                (marginally slower)
-</pre>
+<img src="4500-graph.png" width="70%" style="display: block; margin: auto;"/>
 
 </p>