gstat more writes per seconds than there are seconds per write

[Ronald Klop]

On Thu, 08 Mar 2018 11:20:10 +0100, Bernd Walter <ticso at cicely7.cicely.de>  
wrote:

> On Thu, Mar 08, 2018 at 11:06:23AM +0100, Ronald Klop wrote:
>> Hello,
>>
>> I'm confused by this output.
>> w/s = 5, but ms/w is 1108; how can I put 5 writes in a second if the
>> average write takes more than a second?
>
> It is the time a request has to wait until it is done.
> But your L(q) says that 17 are queued.

Thanks, that makes sense.
Any ideas how to retrieve the ms/w without the time-in-queue included?

Regards,
Ronald.



>
>> Is my SD card super parallel? :-)
>
> Maybe, maybe not, flash device vendors don't tell how they work
> internally, which is a shame, but you can only request a single
> transaction with an SD card.
> On USB sticks you might be able to do tagged command queuing,
> not that many support that...
> Nevertheless you can always queue more than one request at the OS layer.
>
>> Sometimes the numbers are even higher.
>>
>> dT: 1.010s  w: 1.000s
>>  L(q)  ops/s r/s kBps ms/r    w/s   kBps   ms/w   %busy Name
>>    17      5   0    0  0.0      5    420   1108   81.7  mmcsd0
>>     0      0   0    0  0.0      0      0    0.0    0.0  da0
>>     0      0   0    0  0.0      0      0    0.0    0.0  mmcsd0s1
>>    17      5   0    0  0.0      5    420   1108   81.7  mmcsd0s2
>>     0      0   0    0  0.0      0      0    0.0    0.0   
>> msdosfs/MSDOSBOOT
>>    17      5   0    0  0.0      5    420   1108   81.7  mmcsd0s2a
>>    17      5   0    0  0.0      5    420   1108   81.7  ufs/rootfs
>>
>> [root at rpi2 ~]# uname -a
>> dmesg | grep mmc
>> FreeBSD rpi2 11.1-RELEASE-p6 FreeBSD 11.1-RELEASE-p6 #0 r328567: Tue Jan
>> 30 20:10:37 CET 2018
>> root at rpi2:/mnt/usbdisk/usr/obj/mnt/usbdisk/usr/src/sys/RPI2  arm
>>
>> [root at rpi2 ~]# dmesg | grep mmc
>> mmc0: <MMC/SD bus> on sdhci_bcm0
>> mmc0: CMD8 failed, RESULT: 1
>> mmcsd0: 2GB <SD SMI   1.0 SN 1736A86C MFG 05/2007 by 27 SM> at mmc0
>> 41.6MHz/4bit/65535-block
>>
>> Regards,
>> Ronald.
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