Hi Neil,
Any findings on some of the logs I shared earlier?
Thanks in advance for reply. I'm having trouble booting 3.12 kernel,
should probably sort it out soon and come back with results.
Manish
On 12/10/2014 01:29 PM, Manish Awasthi wrote:
Here is the perf report for the tests run on 3.6-11 and 3.18.
Compating both the results, it just appears that raid in older version
is busier than it is with the latest version. I will also monitor the
system activity via `perf top` now. Also, I should be back with
results on 3.12 by the weekend
Manish
On 12/09/2014 01:56 PM, Manish Awasthi wrote:
this time with attachment:
manish
On 12/09/2014 01:54 PM, Manish Awasthi wrote:
resending:
dirty_ratio same for both the kernels.
vm.dirty_background_bytes = 0
vm.dirty_background_ratio = 10
vm.dirty_bytes = 0
vm.dirty_expire_centisecs = 3000
vm.dirty_ratio = 20
vm.dirty_writeback_centisecs = 500
I re-ran the tests with the same set of kernel without enabling
multithread support on 3.18 and measured a few things with perf.
perf-stat-<kernel>.txt: test ran for some time and measured various
parameters.
Meanwhile I'm also running complete test under perf record. I'll
share the results soon.
Manish
On 12/03/2014 11:51 AM, NeilBrown wrote:
On Wed, 26 Nov 2014 13:41:39 +0530 Manish Awasthi
<manish.awasthi@xxxxxxxxxxxxxxxxxx> wrote:
Whatever data I have on comparison is attached, I have
consolidated this
from log files to excel. See if this helps.
raid_3_18_performance.xls shows read throughput to be consistently
20% down
on 3.18 compared to 3.6.11.
Writes are a few percent better for 4G/8G files, 20% better for
16G/32G files.
unchanged above that.
Given that you have 8G of RAM, that seems like it could be some
change in
caching behaviour, and not necessarily a change in RAID behaviour.
The CPU utilization roughly follows the throughput: 40% higher
when write
throughput is 20% better.
Could you check if the value of /proc/sys/vm/dirty_ratio is the
same for both
tests. That number has changed occasionally and could affect
these tests.
The second file, 3SSDs-perf-2-Cores-3.18-rc1 has the "change" numbers
negative where I expected positive.. i.e. negative mean an increase.
Writes consistently have higher CPU utilisation.
Reads consistently have much lower CPU utilization.
I don't know what that means ... it might not mean anything.
Could you please run the tests between the two kernels *with*
RAID. i.e.
directly on an SSD. That will give us a baseline for what changes
are caused
by other parts of the kernel (filesystem, block layer, MM, etc).
Then we can
see how much change RAID5 is contributing.
The third file, 3SSDs-perf-4Core.xls seems to show significantly
reduced
throughput across the board.
CPU utilization is less (better) for writes, but worse for reads.
That is
the reverse of what the second file shows.
I might try running some tests across a set of kernel versions and
see what I
can come up with.
NeilBrown
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