On Apr 21, 2009, at 1:54 PM, Kevin Constantine wrote:
Chuck Lever wrote:
On Apr 20, 2009, at 10:03 PM, Kevin Constantine wrote:
add --data flag to print data cache statistics
print read cache stats from __print_data_cache_stats
It's been a while since I wrote this code... comments below.
Signed-off-by: Kevin Constantine <kevin.constantine@xxxxxxxxxxxxxxxxxxx
>
---
tools/nfs-iostat/nfs-iostat.py | 26 ++++++++++++++++++++------
1 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/tools/nfs-iostat/nfs-iostat.py b/tools/nfs-iostat/nfs-
iostat.py
index 9626d42..d331a72 100644
--- a/tools/nfs-iostat/nfs-iostat.py
+++ b/tools/nfs-iostat/nfs-iostat.py
@@ -220,14 +220,20 @@ class DeviceData:
"""Print the data cache hit rate
"""
nfs_stats = self.__nfs_data
- app_bytes_read = float(nfs_stats['normalreadbytes'])
+ app_bytes_read = float(nfs_stats['normalreadbytes'] +
nfs_stats['directreadbytes'])
if app_bytes_read != 0:
- client_bytes_read =
float(nfs_stats['serverreadbytes'] - nfs_stats['directreadbytes'])
- ratio = ((app_bytes_read - client_bytes_read) *
100) / app_bytes_read
-
+ read_bytes_from_server =
float(nfs_stats['serverreadbytes'])
+ directio_bytes_from_server =
float(nfs_stats['directreadbytes'])
+ standard_read_bytes_from_server =
read_bytes_from_server - directio_bytes_from_server
+ cached_read_bytes = float(app_bytes_read -
read_bytes_from_server)
I'm not sure why you are reversing the sense of this computation.
"directreadbytes" is the count of bytes that applications read with
O_DIRECT. These are never cached, but they are counted in
"serverreadbytes", so my logic subtracts them before computing the
hit ratio. Was there some accounting problem you found? (If there
was, it's worth stating that explicitly in the patch description).
Originally you had app_bytes_read = normalreadbytes, but that's not
entirely true, since an app might be reading with O_DIRECT,
therefore app_bytes_read should probably be normal + direct.
client_bytes_read seemed ambiguous to me, is that bytes being read
by the host client from the server, bytes being read by the nfs
client process? read_bytes_from_server seemed more logical, but in
the diff block below, I've removed that altogether, and am just left
with cached_read_bytes.
I'd rather not change the way the ratio is computed, unless you see a
loss of precision. The way I had it minimizes the possibility of an
overflow during the computation. If you want to rename the variables
to clarify it that's OK, I guess.
+ ratio = (cached_read_bytes / app_bytes_read) * 100
The other functions use (x * 100) / y -- I seem to recall there are
rounding errors if you do it the way you've done it here, but I
don't remember exactly what the issue was. But you are changing
this one so it is different than the all the other similar
computations. Can you state your reason?
since cached_read_bytes = app_bytes_read - client_bytes_read, i used
(cached_read_bytes / app_bytes_read) * 100, but that is the same as
(cached_read_bytes * 100) / app_bytes_read if you'd rather see that.
The latter usually gives us better precision in the calculated result.
new diff block below (if it all checks out, i'll send the whole
patch, unless you'd rather just see that.)
diff --git a/tools/nfs-iostat/nfs-iostat.py b/tools/nfs-iostat/nfs-
iostat.py
index 9626d42..7dae659 100644
--- a/tools/nfs-iostat/nfs-iostat.py
+++ b/tools/nfs-iostat/nfs-iostat.py
@@ -220,14 +220,17 @@ class DeviceData:
"""Print the data cache hit rate
"""
nfs_stats = self.__nfs_data
- app_bytes_read = float(nfs_stats['normalreadbytes'])
+ app_bytes_read = float(nfs_stats['normalreadbytes'] +
nfs_stats['directreadbytes'])
if app_bytes_read != 0:
- client_bytes_read = float(nfs_stats['serverreadbytes']
- nfs_stats['directreadbytes'])
- ratio = ((app_bytes_read - client_bytes_read) * 100) /
app_bytes_read
-
+ cached_read_bytes = float(app_bytes_read -
float(nfs_stats['serverreadbytes']))
+ ratio = (cached_read_bytes * 100) / app_bytes_read
print
- print 'app bytes: %f client bytes %f' %
(app_bytes_read, client_bytes_read)
- print 'Data cache hit ratio: %4.2f%%' % ratio
+ print '%10s %15s %15s %15s %7s' % ("Data Read:", "From
Server", "From Cache", "Total", "Hit %")
+ print '%10s %13.4fMB %13.4fMB %13.4fMB %6.2f%%' % ("", \
+
float(nfs_stats['serverreadbytes']) / 1024.0 / 1024.0, \
+ cached_read_bytes /
1024.0 / 1024.0, \
+ app_bytes_read /
1024.0 / 1024.0, \
+ ratio)
def __print_attr_cache_stats(self, sample_time):
"""Print attribute cache efficiency stats
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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