LZ4 compression

[behlendorf]

Add the LZ4 compression algorithm which was recently merged in to Illumos, illumos/illumos-gate@a6f561b

[edillmann]

I will take a look to get this working

[edillmann]

Hi,

@behlendorf :Could you take a look to this commit :edillmann@6e744ad

This code "work's for me".

I didn't try to use slab's in this because i don't know where i should add the pool allocation and freeing code.

Regards,
Eric

[behlendorf]

@edillmann It looks good, but let's get the code for the kmem cache added and then I'll do some more careful review and testing. My suggestion would be to initialize the kmem cache through zio_init() which already takes care of various other zio related caches. Something like this:

module/zfs/zio.c

void
zio_init(void) {
        ...
        lz4_init()
        zio_inject_init();
}

void
zio_fini(void) {
        ...
        lz4_fini();
        zio_inject_fini();
}

module/zfs/lz4.c

static kmem_cache_t *lz4_cache;

void
lz4_init(void)
{
        lz4_cache = kmem_cache_create("lz4_cache",
            24 * 1024, 0, NULL, NULL, NULL, NULL, NULL, 0);
}

void
lz4_fini(void)
{
        kmem_cache_destroy(lz4_cache);
}

[edillmann]

Et voila : edillmann@cda42be

@behlendorf : Could you take a look at this commit.

I tried to follow illumos as much as possible. But removed dead (unused) code.

[behlendorf]

@edillmann Comments inline, it largely looks good! If you can fix the lingering issues and open a pull request I'll give it another look.

[csiden]

I tried to follow illumos as much as possible. But removed dead (unused) code.

@edillmann Do we have dead code upstream we should be removing or is it dead code due to linux specific changes?

[behlendorf]

@csiden This version drops the following unused functions which do appear in the Illumos upstream version.

static int real_LZ4_uncompress(const char *source, char *dest, int osize);
static int LZ4_compressBound(int isize);

I'd also suggest dropping the _MSC_VER blocks unless you plan on building Illumos with Visual Studio...

[csiden]

Thanks. I checked with Sašo who says he left those in intentionally to make it easier to to apply future patches from upstream LZ4 development. So, I probably won't go out of my way to remove the dead code from illumos until we see how frequent these updates are.

[behlendorf]

9759c60 Illumos #3035 LZ4 compression support in ZFS and GRUB