From: Eric Blake <eblake@redhat.com>
Date: Sat, 26 Oct 2019 15:56:07 +0000 (-0500)
Subject: 4500: Replace <pre>-graph with nicer image.
X-Git-Url: http://git.annexia.org/?a=commitdiff_plain;h=ba71c5150cb2b2dda38e1558f94496b4a98819b5;p=libguestfs-talks.git

4500: Replace <pre>-graph with nicer image.
---

diff --git a/2019-kvm-forum/4500-data.ods b/2019-kvm-forum/4500-data.ods
new file mode 100644
index 0000000..1d14d5b
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diff --git a/2019-kvm-forum/4500-graph.png b/2019-kvm-forum/4500-graph.png
new file mode 100644
index 0000000..fd4ced2
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diff --git a/2019-kvm-forum/4500-new-qemu-flag.html b/2019-kvm-forum/4500-new-qemu-flag.html
index 9832471..ea729bb 100644
--- a/2019-kvm-forum/4500-new-qemu-flag.html
+++ b/2019-kvm-forum/4500-new-qemu-flag.html
@@ -5,51 +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>
-
-Or maybe a graph of demo results:
-<pre>
-     |                                   B
-   12|
-     |
-     |
-     |
-     |
-     |
-     |
-     |   A B
-   8 |                     B                           B          B
-     |
-     |
-     |
- t   |
- i   |
- m   |
- e   |                   A                           A
-   4 |                                 A                        A
-     |
-     |
-     |
-     |
-     |
-     |
-     |
-   0 +----------------------------------------------------------------
-       just WRITE   WRITE_ZEROES     blind         FAST_ZERO  FAST_ZERO
-                    on every hole    pre-zeroing   missing    supported
-</pre>
+<img src="4500-graph.png" width="70%" style="display: block; margin: auto;"/>
 
 </p>