Thread: [ANNOUNCE] CSSU-thumb thread - stable Thumb2 on N900
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freemangordon is offline freemangordon
2012-06-15 , 06:56
Posts: 3,074 | Thanked: 12,964 times | Joined on Mar 2010 @ Sofia,Bulgaria
#118
Originally Posted by szopin View Post
Same as comparisons of class 10 vs class 4 SD cards. Random readwrites make all the differnce for something like booting ubuntu. For HD recording none. In different tests you will get different answers. Try reads from rootfs of highly compressed data like binaries/.o's. Totally different results when writing 1010101... sequentially, all kind of algorithms kick in in between your test and actual write(/read). Best method to check is just starting microb as Nokia made it (rootfs) while clocking and/or camcording time. Restart, move to opt, symlink, restart, clock it and camcord it again and compare. No place for placebo bias.
You're missing my point, it is not about the writes at all, rootfs is much faster on writes, but that does not matter when we're talking about executable code . Is is all about the read operations, and there is where rootfs is not only slower, but consumes 90% CPU time to achieve that slowness. BTW the reason i choose 95MB file to do the read test was to get rid of cache/buffers/whatever effects on the speed.

Also have in mind that there is no performance penalty for doing random reads on flash (i.e. /opt) it is only write operations that are affected.

Except for easy test confirming compression is taking place (so probably not an urban legend) I cannot tell much more. As this is very undetailed ground, who knows, maybe there is a HW solution Nokia implemented for compressing rootfs on the go and it should be(is?) faster. I definitely did not say it is slower by using CPU time (probably should have, seems logical), there might be a compression chip doing it (slowness could be introduced by it or by use case, 10kb txt file could go faster maybe, no idea, but microb starts faster for me from opt so that was my conclusion)
Nah, there is no such thing like compression chip, it is the standard ubifs de/compression and it uses CPU. I definitely say it is slower, as my test ( the "time cat" one) shows the maximum reading speed achieved when there is noone else using the CPU. Imagine what happens with that speed when there are several processes using the CPU.

The case is closed for me, expect a new update (hopefully today) which moves Qt back to /opt.
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Last edited by freemangordon; 2012-06-15 at 07:00.
 

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