I have an older Droid Incredible running Cyanogenmod 7.2. Recently, I've noticed some sluggishness on the phone that doesn't seem limited to a single app. The CPU Usage Plus app (which I think just runs top) often reports that the mmcqd\2 process is using up a lot of CPU (sometimes 50-60%). Googling around, it seems that this process is somehow related to SD card access.

Is there any way for me to diagnose in more detail what exactly is causing this process to use so much CPU, e.g., by seeing what other process is accessing the SD card? Could re-formatting the SD card help? Or could CPU Usage Plus be leading me astray? I have some apps installed on the SD card, and I could try moving them all back to the phone, but it would be nice to figure out a more detailed diagnosis before trying random solutions.

  • Do you happen to be running A2SD on your phone? I had a similar experience on my HTC Desire some time ago, and it was due to having moved both app-data and Dalvik cache to sd-ext. I tried different configurations and moving app-data back to where it was seem to give the best performance for me. There are sources that say otherwise though: android.stackexchange.com/questions/20255/… – Void Dec 20 '12 at 7:08
  • Hey, not running A2SD; I'm pretty sure both Dalvik cache and app-data are on internal storage. I ended up formatting my SD card (after a backup), and things seem to be happier now (I don't have any apps on my SD card now). But, I'm still hoping someone will know a more principled way to diagnose the exact problem. – msridhar Dec 21 '12 at 17:56

So I seem to have addressed this issue, but basically by trial and error. I tried formatting the SD card, but that didn't fix the problem. Finally, I gave up and re-flashed the phone with a full wipe, and then re-installed my apps one by one. Eventually, I found that the Amazon Appstore app was a cause of the problem. Without Amazon Appstore, my phone is much snappier, and I haven't seen mmcqd popping up in CPU usage. (I haven't re-installed every single app I had before, so there could have been other troublemakers.) So, problem fixed for now, but I would hope there is a better way to figure out these types of issues.


One way of diagnosing the offending CPU hog application is to open your application manager while your CPU Usage bars are overlayed. One by one open each potential suspect (Start with your list of downloaded apps from the app store) and select 'Force Stop' while watching the CPU usage bar. If you get a significant drop then you have found the (or one of the) problems. Remove that app. Note that i could be an app that you have had installed for a long time and so you 'trust' it, however a recent update may have changed its usage profile (sending constant checks/polling/whatever to check for status/notifications/updates/etc from whatever site the app is associated with is a typical app abuse symptom.

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