Messages in this thread | | | From | Phillip Lougher <> | Subject | [PATCH 0/3] Squashfs: Directly decompress into the page cache for file data | Date | Fri, 11 Oct 2013 07:19:37 +0100 |
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This patch-set introduces an implementation of squashfs_readpage() that directly decompresses into the page cache.
It first generalises the decompressors by adding a page handler abstraction. This adds helpers to allow the decompressors to access and process the output buffers in an implementation independant manner.
It then adds a read_page() implementation for file data that uses the page handler abstraction to push down the necessary kmap_atomic/kunmap_atomic operations on the page cache buffers into the decompressors. This enables direct copying into the page cache without using the slow kmap/kunmap calls.
The code detects when multiple threads are racing in squashfs_readpage() to decompress the same block, and avoids this regression by falling back to using an intermediate buffer.
This patch enhances the performance of Squashfs significantly when multiple processes are accessing the filesystem simultaneously because it not only reduces memcopying, but it more importantly eliminates the lock contention on the intermediate buffer.
Using single-threaded decompression.
dd if=file1 of=/dev/null bs=4096 & dd if=file2 of=/dev/null bs=4096 & dd if=file3 of=/dev/null bs=4096 & dd if=file4 of=/dev/null bs=4096
Before:
629145600 bytes (629 MB) copied, 45.8046 s, 13.7 MB/s
After:
629145600 bytes (629 MB) copied, 9.29414 s, 67.7 MB/s
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