RPi2 extremely slow on an update with many pauses

Raspberry Pi 2

RPi2 extremely slow on an update with many pauses

Postby mags » Sat Nov 07, 2015 10:21 pm

I have a new RPi2 with an 8GB class 10 microSD. I am finding that on a simple system update, pacman pauses for minutes at a time whilst writing data. Is there something known with the RPi2 and writing data like a firmware bug or something I have misconfigured that would explain it (only 1 partition that is ext4 with relatime mount option per ArchARM defaults)?

My system just the base install with a few packages but nothing major yet.

As a test case, I just updated the system as shown below. I sat here with a stop watch to illustrate:
Code: Select all
# pacman -Syu
...
resolving dependencies...
looking for conflicting packages...

Packages (8) linux-raspberrypi-4.1.12-2  raspberrypi-firmware-20151107-1  raspberrypi-firmware-bootloader-20151107-1
             raspberrypi-firmware-bootloader-x-20151107-1  raspberrypi-firmware-examples-20151107-1
             raspberrypi-firmware-tools-20151107-1  sudo-1.8.15-1  texinfo-6.0-1

Total Installed Size:  88.32 MiB
Net Upgrade Size:       0.53 MiB

:: Proceed with installation? [Y/n]
(8/8) checking keys in keyring                                               [############################################] 100%
(8/8) checking package integrity                                             [############################################] 100%
(8/8) loading package files                                                  [############################################] 100%
(8/8) checking for file conflicts                                            [############################################] 100%
(8/8) checking available disk space                                          [############################################] 100%
(1/8) upgrading linux-raspberrypi                                            [############################################] 100%
>>> Updating module dependencies. Please wait ...
(2/8) upgrading raspberrypi-firmware-bootloader                              [############################################] 100%
(3/8) upgrading raspberrypi-firmware-bootloader-x                            [############################################] 100%
(4/8) upgrading raspberrypi-firmware-tools                                   [############################################] 100%
(5/8) upgrading raspberrypi-firmware-examples                                [############################################] 100%
(6/8) upgrading raspberrypi-firmware                                         [############################################] 100%
(7/8) upgrading sudo                                                         [############################################] 100%
(8/8) upgrading texinfo                                                      [############################################] 100%


The first pause started on 6/8 where pacman just seemed to freeze for 20 sec.
2nd pause started on 7/8 about 66 % through it where pacman froze for 21 sec.
3rd pause happened on 8/8 just after it hit 100 % through it where pacman froze for 1m14sec.

The total time it took to install these packages was 3m33sec.
mags
 
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Re: RPi2 extremely slow on an update with many pauses

Postby moonman » Sat Nov 07, 2015 10:53 pm

Seems normal on an SD card.
1. Not all class 10 cards are the same. There are slower there are faster ones out there. Try the ones with UHS-I logo.
2. Don't know how fast the RPI sd card reader is, but it could be a bottleneck too.

It freezes because those are large packages. It froze right at the end because pacman is doing 'sync' which flushes all buffers to disk/sd card.
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Re: RPi2 extremely slow on an update with many pauses

Postby graysky » Sun Nov 08, 2015 10:14 am

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Re: RPi2 extremely slow on an update with many pauses

Postby graysky » Sun Nov 08, 2015 12:21 pm

I've been reading a bit about this and indeed, there is much ambiguity circulating around the internet about these socalled class 10 cards.

I propose getting some data to confirm. CrystalMark is a common benchmarking util but it is for windows. Iozone on the other hand is linux native and is available in the AUR. I compiled v3.434 for both ARMv6 and ARMV7 which I am hosting on repo-ck.com:

For ARMv6: http://repo-ck.com/ARM/iozone-3_434-1-armv6h.pkg.tar.xz
For ARMv7: http://repo-ck.com/ARM/iozone-3_434-1-armv7h.pkg.tar.xz

I propose having you and anyone else interested running the benchmark. Do it 3 times to get a good sense of reproducible. Here is it on my RPi2 using a generic "Class 10" card that came with the thing as part of a hardware bundle (from amazon).
Code: Select all
% iozone -e -I -a -s 10M -r 4k -i 0 -i 1 -i 2

What I believe to be important are the last two columns corresponding to the random reads and random writes. Please post your output along with a detailed description of the memory card (brand, model, capacity, etc.).

Code: Select all
Brand: Kingston
Capacity: 8GB
Model: unknown
Class: 10
Other: "31414-012.A00LF"

                                                                                random    random
              kB  reclen    write  rewrite    read    reread    read     write
           10240       4      919      996     6324     6355     5672      168
           10240       4      964      996     6311     6327     5648      165
           10240       4      883      954     6391     5035     5726      170
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Re: RPi2 extremely slow on an update with many pauses

Postby graysky » Sun Nov 08, 2015 10:57 pm

I just bought a SanDisk Ultra (SDSQXNE-016G-GN6MA) and it's about 20x faster in the random writes. Amazing difference for $14.

Code: Select all
Brand: SanDisk
Capacity: 16GB
Model: Extreme
Class: UHS-1
Other: SDSQXNE-016G-GN6MA
                                                    random    random
              kB  reclen    write  rewrite    read    reread    read     write
           10240       4     2979     3441     7325     7336     7388     3371
           10240       4     2998     3426     7331     7336     7408     3334
           10240       4     3188     3362     7326     7333     7383     3321


Thanks for the suggestion, Moonman.

EDIT: I added the salient info from this thread to the wiki page. To echo the key benchmarks between the class 10 card that came with the bundle, and the UHS1 SanDsik I recently purchased:

* Synthetic benchmark (Random Writes) were 20x faster on the SanDisk.
* Installing the pre-downloaded base-devel group as 17x faster on the SanDisk.
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Re: RPi2 extremely slow on an update with many pauses

Postby mags » Thu Dec 17, 2015 2:53 pm

You were right about the card, graysky. I bought the SDSQXNE-016G-GN6MA from amazon and I get benchmark numbers like yours and the pi is very fast now. Thank you!
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Re: RPi2 extremely slow on an update with many pauses

Postby tpfkanep » Wed Dec 23, 2015 6:57 pm

Brand: SanDisk
Capacity: 8GB
Model: unknown
Class: 10
Other: unknown
Code: Select all
                                                             random  random
   KB  reclen   write rewrite    read    reread    read   write
10240       4    1091    1115     5873     5880    5336     920


Same SD card as above but /boot/config.txt with: dtoverlay=mmc,overclock_50=63
Code: Select all
                                                             random  random
   KB  reclen   write rewrite    read    reread    read   write
10240       4    1656    1906     7985     7993    7240     927


Do not have a UHS-1 SD card...

I just uncommented dtoverlay=mmc,overclock_50=63 in /boot/config.txt and have been running fine for a couple of hours. Last time I used it (on a B+) it was a bit unstable... YMMV.
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Re: RPi2 extremely slow on an update with many pauses

Postby MST » Tue Dec 29, 2015 12:51 am

Another data point on a Sandisk Ultra 16GB ($7 from China to UK)

Order description said
DSDQUAN-16G-G4A

Retail packaging said microSDHC UHS-1
SDSQUNC-016G-ZN6MA 80MB/533X

Code: Select all
    kB  reclen    write  rewrite    read    reread    read     write
10240       4     2788     3033     7365     7377     7320     1530


Must buy the Extreme SDSQXNE-016G-GN6MA next time
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