Re: nvme SSD and poor performance
On 8/17/21 2:54 AM, Pierre Willaime wrote:
> I have a nvme SSD (CAZ-82512-Q11 NVMe LITEON 512GB) on debian stable
> (bulleye now).
>
> For a long time, I suffer poor I/O performances which slow down a lot of
> tasks (apt upgrade when unpacking for example).
On 8/20/21 1:50 AM, Pierre Willaime wrote:
Thanks all.
I activated `# systemctl enable fstrim.timer` (thanks Linux-Fan).
But I do not think my issue is trim related after all.
I agree.
I have always a
lot of I/O activities from jdb2 even just after booting and even when
the computer is doing nothing for hours.
Here is an extended log of iotop where you can see jdb2 anormal
activities: https://pastebin.com/eyGcGdUz
Was your command something like this?
# iotop -o -k -t -q -q -q > iotop.out
I cannot (yet) find what process is generating this activities. I tried
to kill a lot of jobs seing in atop output with no results.
Analyzing the first ten minutes worth of data with an improvised Perl
script:
index of field 'read_bw'
1256840.19 firefox-esr
77926.07 apt
316.08 perl
22.74 dpkg
15.27 [kworker/6:0-events]
index of field 'write_bw'
220512.79 thunderbird
29613.87 firefox-esr
23221.20 dpkg
15211.66 [jbd2/nvme0n1p2-]
5529.57 [dpkg]
4148.09 systemd-journald
1699.13 perl
533.28 mandb
507.15 apt
145.61 rsyslogd
131.59 atop
115.77 syncthing
46.35 xfce4-terminal
38.60 smartd
15.48 Xorg
15.44 NetworkManager
7.64 bash
index of field 'swap_percent'
index of field 'io_wait_percent'
12427.58 [jbd2/nvme0n1p2-]
1334.15 firefox-esr
568.91 dpkg
385.31 thunderbird
293.57 mandb
99.99 syncthing
64.82 [kworker/13:3-events_freezable_power_]
63.86 smartd
55.12 [kworker/u32:3+flush-259:0]
38.64 [kworker/u32:2-flush-259:0]
25.27 [kworker/u32:3-events_unbound]
23.13 [kworker/4:0-events_freezable_power_]
22.68 [kworker/u32:2-events_unbound]
21.55 apt
12.51 [kworker/u32:1-ext4-rsv-conversion]
9.87 [kworker/u32:2-ext4-rsv-conversion]
9.63 [kworker/9:1-events]
8.90 [kworker/u32:1-flush-259:0]
8.58 perl
8.11 [kworker/9:1-events_freezable_power_]
5.85 [dpkg]
4.33 [kworker/u32:3-ext4-rsv-conversion]
4.26 NetworkManager
3.57 [kworker/13:3-mm_percpu_wq]
2.85 [kworker/9:1-mm_percpu_wq]
2.71 [kworker/4:0-mm_percpu_wq]
0.40 [kworker/13:3-events] [kworker/4:0-events]
0.38 [kworker/6:1-events]
0.36 [kworker/9:1-rcu_gp]
0.30 [kworker/u32:3-flush-259:0]
0.26 [kworker/6:0-events_freezable_power_]
0.16 systemd-journald
0.03 [kworker/6:0-events]
I appears:
- firefox-esr used the most read bandwidth -- 1256840.19 K/s total
- thunderbird used the most write bandwdith -- 220512.79 K/s total
- No processes were swapping.
- jbd2/nvme0n1p2- waited the longest for I/O -- 12427.58 % total
Both apt(8) and dpkg(1) were also running and using a small amount of
I/O. While I may leave Firefox and Thunderbird running when installing
a package or two, I shut them down for updates and upgrades. Was the
iotop data collected during a long-running upgrade?
AIUI the jbd2/nvme0n1p2 I/O corresponds to the bottom half of the kernel
(e.g. device driver interface, DDI) in response to I/O via the top half
of the kernel (e.g. application programming interface, API). The way to
reduce jdb2 I/O is to reduce application I/O.
> On 8/17/21 7:07 AM, Dan Ritter wrote:
>> I don't think you have a significant performance problem, but
>> you are definitely feeling some pain -- so can you tell us more
>> about what feels slow? Does it happen during the ordinary course
>> of the day?
Program are slow to start. Sometimes there is a delay when I type
(letters are displayed few second after typing). Apt unpack take forewer
(5 hours to unpack packages when upgrading to bulleye).
The computer is a recent Dell precision desktop with i9-9900 as CPU, an
NVIDIA GP107GL [Quadro P400] (and the GPU integrated to the CPU). The
nvme SSD is supposed to be a decent one. This desktop is yet a lot
slower than my (more basic) laptop.
Complete system info: https://pastebin.com/zaGVEpae
That's a good workstation. :-)
Firefox and Thunderbird are habitual trouble-makers on my Debian
desktops. I run Xfce with the CPU Graph panel applet. If I leave
Firefox or Thunderbird open long enough, eventually I will see a core
pegged at 100% and the CPU fan will spin up. Both applications keep
working in this state; but a swirling toilet bowl mouse pointer in
Thunderbird is a danger sign -- I have lost e-mail messages when moving
a message produced that symptom. The only cure is to close the
offending program(s) and implement additional measures to duplicate
incoming and outgoing e-mail. My conclusion is that both Firefox and
Thunderbird have multi-threaded programming bugs. The next time either
malfunctions, I may capture some iotop(8) data and analyze it.
I have also noticed that Linux is not very good at sharing I/O between
processes and/or drives. If one process is hammering I/O, any other
processes that attempts I/O will stutter. I have seen this both when
two processes access the same drive and when two processes access
different drives.
The last consideration is that Debian 11.0 has just been released. I
have encountered many problems with Debian *.0 releases over the years,
and typically wait several months and a couple of minor version upgrades
before doing a fresh install and migrating services and data. (The
Debian 10 nouveau driver did not like the NVIDIA Optimus graphics in my
Dell Latitude E6520 laptop until recently -- Debian 10.9?)
I suggest that you do a fresh install of Debian 10.10 and evaluate that.
If you still see problems, try Debian 9.13.
David
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