Journal is not the reason. It's just the first one to hit the bottleneck. It's not logging anything unusual, just normal trafiic. But following your suggestion I checked this card in my Lenovo W541 running F25. I've got average write speed of around 7MB/s. When I sent the same file (2.4 GiB zip) to my PI, and it nearly killed it - 1.5 core constantly occupied by system, rest is blocked by IO waits. But write speed wasn't so much worse: 4.1 MiB/s. Just for curiosity, I wrote the same file onto USB stick attached to my PI - this time it was slower (3.2 MiB/s), but system seemed to be more responsive. So writing is CPU intensive and that makes me wonder what is use_spi_crc option responsible for in mmc_core kernel module and how to check it's current value.
After quick look into module's code I see it is supposed to do some data validation with crc which I think may lead to lots of CPU intensive operations in kernel mode ? How do I check "use_spi_crc" current value? I couldn't find any obvious files in /proc or /sys filesystems. If it's value is "true" than how do I set it to false? Is proper /etc/modprobe.d file entry sufficient or should I play with kernel parameters at startup since it is responsible for accessing root filesystem ? regards, marcinek 2017-05-08 14:55 GMT+02:00 Richard Ryniker <[email protected]>: > If the slowdown is due to log writes, what is written into your journal? > > It may be awkward to access the journal using the RPi, but move the SD > card to another Fedora system (many laptops have flash card readers built > in, or use a USB device) and a "smoking gun" may be obvious. The journal > format does not depend on machine architecture. Use the --directory= > argument for journalctl. >
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