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Another extremely useful graphical depiction is the chunk size distribution. For instance, this information is often used to understand how efficient the user application is when it comes to optimize the write operations for maximizing the e.MMC lifetime. The pie on the left refers to the read operations, while the other one refers to the write operations. To interpret the result, one needs to take into account how the workload was implemented.
[[File:MISC-TN-017-eMMC-chart2-chunk-size.png|center|thumb|600x600px|Chunk size distribution]]
Basically, it makes use of two applications: <code>[https://man7.org/linux/man-pages/man1/dd.1.html dd]</code> and <code>stressapptest</code>. <code>dd</code> was specified to use 4-kByte data chunks (<code>bs=4k</code>). <code>stressapptest</code> uses 512-byte chunks instead because the <code>--write-block-size</code> parameter was not used (for more details please refer to the [https://github.com/stressapptest/stressapptest/blob/e6c56d20c0fd16b07130d6e628d0dd6dcf1fe162/src/worker.cc#L2615 source code]). As a result, one would expect that the majority of accesses are 512 bytes and 4 kByte. The charts clearly show that this is not the case. Most of the accesses are 512kBinstead. This is a blatant example of how the algorithms of the file systems and the kernel block driver optimize can alter the accessesissued at application levels for optimization purposes.
==== Appendix 1: source code example ====
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=== Device's built-in advanced functionalities ===
As explained in [[#Example: embedded Linux system equipped with an e.MMC|this section]], e.MMC manufacturers usually implement proprietary registers to get detailed information about the status of the device.
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=Power failures=
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Interestingly, JEDEC standard also defines a set of registers (<code>VENDOR_PROPRIETARY_HEALTH_REPORT</code>) that vendors are free to use for providing further, fine-grained information about the device's health status. Engineers and system integrators are supposed to contact the e.MMC manufacturer to have more detailsget the required tools for accessing such registers.
= References =
