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0d455c12c6
This introduces an implementation of squashfs_readpage_block()
that directly decompresses into the page cache.
This uses the previously added 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-thread 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
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reviewed-by: Minchan Kim <minchan@kernel.org>
82 lines
2.0 KiB
C
82 lines
2.0 KiB
C
#ifndef PAGE_ACTOR_H
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#define PAGE_ACTOR_H
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/*
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* Copyright (c) 2013
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* Phillip Lougher <phillip@squashfs.org.uk>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*/
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#ifndef CONFIG_SQUASHFS_FILE_DIRECT
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struct squashfs_page_actor {
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void **page;
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int pages;
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int length;
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int next_page;
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};
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static inline struct squashfs_page_actor *squashfs_page_actor_init(void **page,
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int pages, int length)
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{
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struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
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if (actor == NULL)
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return NULL;
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actor->length = length ? : pages * PAGE_CACHE_SIZE;
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actor->page = page;
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actor->pages = pages;
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actor->next_page = 0;
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return actor;
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}
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static inline void *squashfs_first_page(struct squashfs_page_actor *actor)
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{
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actor->next_page = 1;
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return actor->page[0];
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}
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static inline void *squashfs_next_page(struct squashfs_page_actor *actor)
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{
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return actor->next_page == actor->pages ? NULL :
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actor->page[actor->next_page++];
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}
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static inline void squashfs_finish_page(struct squashfs_page_actor *actor)
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{
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/* empty */
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}
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#else
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struct squashfs_page_actor {
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union {
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void **buffer;
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struct page **page;
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};
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void *pageaddr;
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void *(*squashfs_first_page)(struct squashfs_page_actor *);
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void *(*squashfs_next_page)(struct squashfs_page_actor *);
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void (*squashfs_finish_page)(struct squashfs_page_actor *);
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int pages;
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int length;
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int next_page;
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};
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extern struct squashfs_page_actor *squashfs_page_actor_init(void **, int, int);
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extern struct squashfs_page_actor *squashfs_page_actor_init_special(struct page
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**, int, int);
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static inline void *squashfs_first_page(struct squashfs_page_actor *actor)
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{
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return actor->squashfs_first_page(actor);
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}
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static inline void *squashfs_next_page(struct squashfs_page_actor *actor)
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{
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return actor->squashfs_next_page(actor);
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}
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static inline void squashfs_finish_page(struct squashfs_page_actor *actor)
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{
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actor->squashfs_finish_page(actor);
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}
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#endif
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#endif
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