Chuck Lever wrote:
Hi Kevin-
On Apr 21, 2009, at 9:42 PM, Kevin Constantine wrote:
I rolled the read cache, and write patches into a single patch below.
add --data flag to print data cache statistics
print read cache stats from __print_data_cache_stats
print stats about bytes written by NFS
Signed-off-by: Kevin Constantine <kevin.constantine@xxxxxxxxxxxxxxxxxxx>
---
tools/nfs-iostat/nfs-iostat.py | 28 ++++++++++++++++++++++------
1 files changed, 22 insertions(+), 6 deletions(-)
diff --git a/tools/nfs-iostat/nfs-iostat.py
b/tools/nfs-iostat/nfs-iostat.py
index 9626d42..cb3da59 100644
--- a/tools/nfs-iostat/nfs-iostat.py
+++ b/tools/nfs-iostat/nfs-iostat.py
@@ -220,14 +220,22 @@ 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'])
Again, I object to this particular change. The reason for the current
computation is to retain precision and mitigate the chance of an
overflow. Reversing the sense of this computation (by introducing the
addition above) increases the probability of overflow here. Remember
that over time, these numbers can grow exceptionally large.
If you think you need this change, you do need to provide some
justification for the reorganization in the patch description. Why is
the current code inadequate?
I've changed my opinion on how the cache hit ratio should be computed and now agree with you. I was thinking that direct reads should negatively
impact the ratio, but that doesn't make a whole lot of sense.
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
In my opinion, displaying O_DIRECT reads right next to the cache hit
ratio is deceptive. This is why I did not include the O_DIRECT counts
here. They have no impact on the page cache hit ratio, as O_DIRECT data
is never cached in the kernel.
I've changed the output considerably this time around. I think it makes more sense, let me know what you think.
nani:/vol/pamtest mounted on /data/pamtest:
op/s rpc bklog
3452.00 13.16
read: ops/s kB/s kB/op retrans avg RTT (ms) avg exe (ms)
3452.000 111407.906 32.273 0 (0.0%) 4.633 8.628
write: ops/s kB/s kB/op retrans avg RTT (ms) avg exe (ms)
0.000 0.000 0.000 0 (0.0%) 0.000 0.000
Network Direct I/O Direct % Total
Read Write Cache Reads Cache Hit % Read Write Read Write Read Write
107.8750MB 0.0000MB 4.1236MB 3.68% 0.0000MB 0.0000MB 0.00% 0.00% 111.9986MB 0.0000MB
+ 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)
If app_bytes_read is zero, we should print a line here that displays
zeroes, as is done in other areas of this code. I know that nfsstat
quells output lines containing all zeros, but other tools (like iostat)
do not. What ends up happening is that when there is no I/O activity,
no lines are produced at all. That is confusing to users when
nfs-iostat is in the "output one line every N seconds" mode.
Agreed. It now prints out zeroes. There are instances where data has been
sent through the NFS stack and counted in the serverbytes counter, but
haven't made it through the userspace stack and haven't been counted so we
get a negative cache hit ratio. In these cases, I'm converting the cache
ratio and cache bytes to zero.
+ bytes_written_by_nfs = float(nfs_stats['serverwritebytes'])
+ if bytes_written_by_nfs != 0:
+ print
+ print '%13s %12s' % ("Data Written:", "To Server")
+ print '%10s %13.4fMB' % ("", bytes_written_by_nfs / 1024.0 /
1024.0)
As you are not dividing by bytes_written_by_nfs, there is no particular
reason to gate this output. I don't see the need for the extra variable
here either. You don't have a similar variable in the read statistics,
for example.
I was thinking the gate was there to prevent non-zero values from printing.
This has been fixed.
You included application and direct read bytes in your read statistics,
but not here. Why not?
The new output prints Network reads/writes, direct reads/writes, total
reads/writes, cache reads, cache ratio and direct i/o ratios for reads/writes.
New Patch below:
add --data flag to print data cache statistics
--data flag prints Network reads/writes, cache reads, cache hit%, Direct I/O reads/writes, Direct I/O% and Total reads/Writes
Signed-off-by: Kevin Constantine <kevin.constantine@xxxxxxxxxxxxxxxxxxx>
---
tools/nfs-iostat/nfs-iostat.py | 53 +++++++++++++++++++++++++++++++++++++---
1 files changed, 49 insertions(+), 4 deletions(-)
diff --git a/tools/nfs-iostat/nfs-iostat.py b/tools/nfs-iostat/nfs-iostat.py
index 9626d42..b9f3a96 100644
--- a/tools/nfs-iostat/nfs-iostat.py
+++ b/tools/nfs-iostat/nfs-iostat.py
@@ -220,14 +220,51 @@ class DeviceData:
"""Print the data cache hit rate
"""
nfs_stats = self.__nfs_data
+ client_bytes_read = 0
+ ratio = 0
+ direct_read_ratio = 0
+ direct_write_ratio = 0
+
app_bytes_read = float(nfs_stats['normalreadbytes'])
+ client_bytes_read = float(nfs_stats['serverreadbytes'] - nfs_stats['directreadbytes'])
+ direct_read_bytes = float(nfs_stats['directreadbytes'])
+ direct_write_bytes = float(nfs_stats['directwritebytes'])
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
+ if direct_read_bytes != 0:
+ direct_read_ratio = float(nfs_stats['directreadbytes']) * 100 / \
+ (app_bytes_read + direct_read_bytes)
+ if direct_write_bytes != 0:
+ direct_write_ratio = float(nfs_stats['directwritebytes']) * 100 / \
+ (direct_write_bytes + float(nfs_stats['normalwritebytes']))
+
+ network_reads_MB = float(nfs_stats['serverreadbytes']) / 1024.0 / 1024.0
+ network_writes_MB = float(nfs_stats['serverwritebytes']) / 1024.0 / 1024.0
+ cached_reads_MB = float(app_bytes_read - client_bytes_read) / 1024.0 / 1024.0
+ direct_reads_MB = float(nfs_stats['directreadbytes']) / 1024.0 / 1024.0
+ direct_writes_MB = float(nfs_stats['directwritebytes']) / 1024.0 / 1024.0
+ total_reads_MB = float(app_bytes_read + nfs_stats['directreadbytes']) / 1024.0 / 1024.0
+ total_writes_MB = float(nfs_stats['normalwritebytes'] + nfs_stats['directwritebytes']) / \
+ 1024.0 / 1024.0
+
+ """ Bytes may have been counted by the NFS stack but haven't been counted by the
+ userspace stack. When this happens, we see negative cache values. Set these
+ to zero to avoid confusion.
+ """
+ if cached_reads_MB < 0:
+ cached_reads_MB = 0;
+ if ratio < 0:
+ ratio = 0;
- print
- print 'app bytes: %f client bytes %f' % (app_bytes_read, client_bytes_read)
- print 'Data cache hit ratio: %4.2f%%' % ratio
+ print
+ print '%18s %51s %20s %22s' % ("Network", "Direct I/O", "Direct %", "Total")
+ print '%10s %12s %13s %14s %8s %12s %10s %9s %12s %12s' % \
+ ("Read", "Write", "Cache Reads", "Cache Hit %", "Read", "Write", \
+ "Read", "Write", "Read", "Write")
+ print '%10.4fMB %10.4fMB %10.4fMB %10.2f%% %10.4fMB %10.4fMB %8.2f%% %8.2f%% %10.4fMB %10.4fMB' % ( \
+ network_reads_MB, network_writes_MB, cached_reads_MB, ratio, direct_reads_MB, \
+ direct_writes_MB, direct_read_ratio, direct_write_ratio, total_reads_MB, \
+ total_writes_MB)
def __print_attr_cache_stats(self, sample_time):
"""Print attribute cache efficiency stats
@@ -390,6 +427,10 @@ class DeviceData:
self.__print_rpc_op_stats('READ', sample_time)
self.__print_rpc_op_stats('WRITE', sample_time)
self.__print_page_stats(sample_time)
+ elif which == 4:
+ self.__print_rpc_op_stats('READ', sample_time)
+ self.__print_rpc_op_stats('WRITE', sample_time)
+ self.__print_data_cache_stats()
#
# Functions
@@ -487,6 +528,10 @@ def iostat_command(name):
if arg in ['-p', '--page']:
which = 3
continue
+
+ if arg in ['--data']:
+ which = 4
+ continue
if arg == sys.argv[0]:
continue
-- 1.6.2.1
--
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