flamegraphs: Improve the title page

[libguestfs-talks.git] / 2019-fosdem / nbdview / README

diff --git a/2019-fosdem/nbdview/README b/2019-fosdem/nbdview/README
index 0f42bd1..ed6bc8e 100644 (file)
--- a/2019-fosdem/nbdview/README
+++ b/2019-fosdem/nbdview/README
@@ -1,3 +1,6 @@
+nbdview
+-------
+
 nbdview is a small Tcl/Tk program that lets you visualize reads and
 writes happening to an nbdkit server in real time.
 
@@ -6,7 +9,16 @@ filter.  For example, using the memory plugin (but any plugin may be
 used):
 
   size=$((64 * 1024 * 1024))
-  nbdkit --filter=log memory size=$size logfile=/tmp/log
+  delay=40ms
+  nbdkit --filter=log --filter=delay \
+         memory \
+         size=$size \
+         logfile=/tmp/log \
+         rdelay=$delay wdelay=$delay &
+
+In this example I have also added a delay which helps to make the
+stuff happening on screen easier to see and more "animated", but it is
+not required.
 
 Then start nbdview.tcl specifying the log file and virtual size:
 
@@ -20,3 +32,27 @@ most 64MB.
 Then you can write to the NBD server using ordinary tools such as
 qemu, qemu-io, guestfish, etc. and observe the reads and writes to the
 disk.
+
+nbdraid
+-------
+
+As above but allowing you to display operations to multiple (RAID)
+devices.
+
+Start N copies of nbdkit like this:
+
+  size=$((64 * 1024 * 1024))
+  delay=40ms
+  rm /tmp/error$i
+  rm /tmp/sock$i
+  nbdkit -U /tmp/sock$i \
+         --filter=error --filter=log --filter=delay \
+         memory \
+         size=$size \
+         logfile=/tmp/log$i \
+         rdelay=$delay wdelay=$delay \
+         error-rate=1 error-file=/tmp/error$i &
+
+Then start nbdraid.tcl:
+
+  ./nbdraid $N $size /tmp/log%d /tmp/error%d