Would be difficult to do and would defeat the purpose of some of the Provide order guarantees for the BIOs all the way down the stack, which Kent Overstreet said they were removed due to unclear semantics,Įspecially for stacked filesystems. He researched them and found that they had been removed In order to reduce the latency of fsync() calls, he is looking at Write and one fsync() by using F2FS atomic writes. A feature has been added to SQLite to avoid one Operations can be expensive and are not needed for F2FS because it is aĬopy-on-write filesystem. Writes to the database end up requiring two writes and two fsync()Ĭalls (first for the journal and then to the final location). To ensure its data has gotten to storage. SQLite performance is another problem area. Time, it can then initiate the garbage-collection process. When it is time to do garbage collection. He would like to add a customized interface that can be called Kim would like to see the garbage collection on the device side get 'horrible code' that only works for ext4 ecryptfs or F2FS no one has had Qualcomm that cannot be pushed upstream, however. There is some hardware encryption code from Makes sense to batch cache-flush commands.įilesystem encryption is mandatory for Android. Ten-second latencies for a single cache-flush command. Some vendors' devices have low latency but others have There is a raceĭifferent UFS devices have different latencies for their cache-flushĬommands. To a list that would be processed by the kthread. A kernel thread (kthread) could be added to issueĭiscards asynchronously during idle time. The solution to the discard performance problem should be fairly

It could perhaps also be used for garbage collection. That Android currently declares a ten-minute idle time at 2am that is usedįilesystem.

Hibernating the device is prioritized, which does not leave much time forĪmir Goldstein suggested doing garbage collection when the device isĬharging he thought that should provide a reasonable solution. But power is a more important consideration, so That needs to be avoided, so UFS must be periodically given some time to do its When garbageĬollection is needed, the performance of even sequential writes drops wayĭown. UFS devices have a 'huge garbage-collection overhead'. The user to think that Android is broken, he said. For example, ext4 will issue a discardĬommand but a UFS device might take ten seconds to process it. In the end, though, the talk did not focus on F2FS and insteadįlash Storage (UFS) devices have high read/write speeds, but can also have Maintainer, and the filesystem-track session was ostensibly about thatįilesystem. (LSFMM), Jaegeuk Kim described some current issues for flash storage,Įspecially with regard to Android. At the 2018 Linux Storage, Filesystem, and Memory-Management Summit

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