Massive performance regression in v2 non-native generator

[PokeMMO]

Even if you supply MmapByteSource's to FileByFileDeltaGenerator, it seems to replace them with RandomAccessFileByteSource's.

https://github.com/google/archive-patcher/blob/v2/generator/src/main/java/com/google/archivepatcher/generator/FileByFileDeltaGenerator.java#L108-L109

https://github.com/google/archive-patcher/blob/v2/shared/src/main/java/com/google/archivepatcher/shared/bytesource/ByteSource.java#L61-L63

The current RandomAccessFileByteSource's implementation seems to suffer extremely hard from seeks, an extremely common operation.

Simply swapping ByteSource.fromFile to always return a MmapByteSource greatly improves performance.

[pspencil]

Yes. That is expected. I will see what I can do.

…

On Sun, 2 Jun 2019, 08:03 PokeMMO, ***@***.***> wrote: Even if you supply MmapByteSource's to FileByFileDeltaGenerator, it seems to replace them with RandomAccessFileByteSource's. https://github.com/google/archive-patcher/blob/v2/generator/src/main/java/com/google/archivepatcher/generator/FileByFileDeltaGenerator.java#L108-L109 https://github.com/google/archive-patcher/blob/v2/shared/src/main/java/com/google/archivepatcher/shared/bytesource/ByteSource.java#L61-L63 The current RandomAccessFileByteSource's implementation seems to suffer extremely hard from seeks, an extremely common operations. Simply swapping ByteSource.fromFile to always return a MmapByteSource greatly improves performance. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#124?email_source=notifications&email_token=AAYQEN63W7UZCF4M36WS663PYNWDXA5CNFSM4HSCA7VKYY3PNVWWK3TUL52HS4DFUVEXG43VMWVGG33NNVSW45C7NFSM4GXEFOOA>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAYQEN4NOHWFU3GREP7MWMDPYNWDXANCNFSM4HSCA7VA> .

[PokeMMO]

I would expect FileByFileDeltaGenerator to keep the same ByteSource implementation that is supplied to it.

Or just use mmap for everything (This is what the JNI lib does)

[Archive-Patcher-Sync-Robot]

I have switched to mmap. It is better but still slower than master. I will need more investigation on how to optimise this.