Messages in this thread | | | Date | Fri, 4 May 2007 14:36:16 +0530 | From | "Satyam Sharma" <> | Subject | Re: [PATCH 2/5] jffs2: Add LZO compression support to jffs2 |
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Hi Richard,
On 5/1/07, Richard Purdie <rpurdie@openedhand.com> wrote: > Add LZO1X compression/decompression support to jffs2. > > LZO's interface doesn't entirely match that required by jffs2 so a > buffer and memcpy is unavoidable. > > Signed-off-by: Richard Purdie <rpurdie@openedhand.com> > --- > [...] > +++ b/fs/jffs2/compr_lzo.c > [...] > +static void *lzo_mem; > +static void *lzo_compress_buf; > +static DEFINE_MUTEX(deflate_mutex); > + > +static void free_workspace(void) > +{ > + vfree(lzo_mem); > + vfree(lzo_compress_buf); > +} > + > +static int __init alloc_workspace(void) > +{ > + lzo_mem = vmalloc(LZO1X_MEM_COMPRESS); > + lzo_compress_buf = vmalloc(lzo1x_worst_compress(PAGE_SIZE)); > + > + if (!lzo_mem || !lzo_compress_buf) { > + printk(KERN_WARNING "Failed to allocate lzo deflate workspace\n"); > + free_workspace(); > + return -ENOMEM; > + } > + > + return 0; > +} > + > +static int jffs2_lzo_compress(unsigned char *data_in, unsigned char *cpage_out, > + uint32_t *sourcelen, uint32_t *dstlen, void *model) > +{ > + unsigned long compress_size; > + int ret; > + > + mutex_lock(&deflate_mutex); > + ret = lzo1x_1_compress(data_in, *sourcelen, lzo_compress_buf, &compress_size, lzo_mem); > + mutex_unlock(&deflate_mutex);
Considering we do have to memcpy() the entire compressed result to the destination output buffer later anyway (note that fs/jffs2/compr_zlib.c doesn't need to do that), do we really gain much by avoiding vmalloc() and vfree() in jffs2_lzo_compress() itself and keeping the workspace buffers pre-allocated? I ask because I always found these global static workspace buffers ugly, and all the associated code + mutex could go away if we make them local to jffs2_lzo_compress() -- as long as it doesn't hurt performance terribly, of course.
Thanks, Satyam - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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