Re: [PATCH v2 8/8] zram: use decompress_noctx

[Sergey Senozhatsky]

On (08/20/15 15:35), Joonsoo Kim wrote:
> Crypto subsystem supports noctx API which doesn't require tfm.
> To get tfm in zram, we need zstrm and it is limited resource.
> If we uses noctx API, we don't need to get zstrm so that
> we get much better performance when zstrm is insufficient.
> 
> This patch restores zram's performance to the time that zram
> doesn't use crypto subsystem.
> 
> Following is zram's read performance number.
> 
> * iozone -t 4 -R -r 16K -s 60M -I +Z -i 0 -i 1
> * max_stream is set to 1
> * Output is in Kbytes/sec
> 
> zram-base vs zram-crypto vs zram-crypto-noctx
> 
> Read		10411701.88	6426911.62	9423894.38
> Re-read		10017386.62	6428218.88	11000063.50
> 
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> ---
>  drivers/block/zram/zcomp.c    | 28 +++++++++++++++++++++++++++-
>  drivers/block/zram/zcomp.h    |  9 ++++++++-
>  drivers/block/zram/zram_drv.c |  9 +++++----
>  3 files changed, 40 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> index d2734f2..86b0c9b 100644
> --- a/drivers/block/zram/zcomp.c
> +++ b/drivers/block/zram/zcomp.c
> @@ -291,8 +291,12 @@ bool zcomp_set_max_streams(struct zcomp *comp, int num_strm)
>  	return comp->set_max_streams(comp, num_strm);
>  }
>  
> -struct zcomp_strm *zcomp_strm_find(struct zcomp *comp)
> +struct zcomp_strm *zcomp_strm_find(struct zcomp *comp, bool decomp)
>  {
> +	/* We don't need decompression context so zstrm neither */
> +	if (decomp && test_bit(ZCOMP_DECOMPRESS_NOCTX, &comp->flags))
> +		return NULL;
> +
>  	return comp->strm_find(comp);
>  }

No. zcomp_strm_find() should never return NULL. And no, I don't like
"if (decomp)" change.


>  
> @@ -307,6 +311,11 @@ int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
>  {
>  	*dst_len = PAGE_SIZE << 1;
>  
> +	if (!zstrm) {
> +		return crypto_comp_compress_noctx(comp->alg, src, PAGE_SIZE,
> +							dst, dst_len);
> +	}
> +
>  	return crypto_comp_compress(zstrm->tfm, src, PAGE_SIZE, dst, dst_len);
>  }
>  
> @@ -316,12 +325,18 @@ int zcomp_decompress(struct zcomp *comp, struct zcomp_strm *zstrm,
>  {
>  	unsigned int size = PAGE_SIZE;
>  
> +	if (!zstrm) {
> +		return crypto_comp_decompress_noctx(comp->alg, src, src_len,
> +							dst, &size);
> +	}
> +
>  	return crypto_comp_decompress(zstrm->tfm, src, src_len,	dst, &size);
>  }
>  
>  void zcomp_destroy(struct zcomp *comp)
>  {
>  	comp->destroy(comp);
> +	crypto_put_comp(comp->alg);
>  	kfree(comp);
>  }
>  
> @@ -344,12 +359,23 @@ struct zcomp *zcomp_create(const char *compress, int max_strm)
>  		return ERR_PTR(-ENOMEM);
>  
>  	comp->name = compress;
> +	comp->alg = crypto_get_comp(compress, 0, 0);
> +	if (!comp->alg) {
> +		kfree(comp);
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	if (crypto_has_compress_noctx(comp->alg))
> +		set_bit(ZCOMP_COMPRESS_NOCTX, &comp->flags);

do you use ZCOMP_COMPRESS_NOCTX algs in this patch set?


> +	if (crypto_has_decompress_noctx(comp->alg))
> +		set_bit(ZCOMP_DECOMPRESS_NOCTX, &comp->flags);
>  
>  	if (max_strm > 1)
>  		zcomp_strm_multi_create(comp, max_strm);
>  	else
>  		zcomp_strm_single_create(comp);
>  	if (!comp->stream) {
> +		crypto_put_comp(comp->alg);
>  		kfree(comp);
>  		return ERR_PTR(-ENOMEM);
>  	}
> diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
> index c47db4d..6c137c8 100644
> --- a/drivers/block/zram/zcomp.h
> +++ b/drivers/block/zram/zcomp.h
> @@ -13,6 +13,11 @@
>  #include <linux/crypto.h>
>  #include <linux/mutex.h>
>  
> +enum {
> +	ZCOMP_COMPRESS_NOCTX,
> +	ZCOMP_DECOMPRESS_NOCTX,
> +};

Can it be handled via crypto api? check if ->foo_noctx() is !NULL ?

>  struct zcomp_strm {
>  	struct crypto_comp *tfm;
>  
> @@ -27,6 +32,8 @@ struct zcomp_strm {
>  struct zcomp {
>  	void *stream;
>  	const char *name;
> +	struct crypto_alg *alg;
> +	unsigned long flags;
>  
>  	struct zcomp_strm *(*strm_find)(struct zcomp *comp);
>  	void (*strm_release)(struct zcomp *comp, struct zcomp_strm *zstrm);
> @@ -39,7 +46,7 @@ ssize_t zcomp_available_show(const char *comp, char *buf);
>  struct zcomp *zcomp_create(const char *comp, int max_strm);
>  void zcomp_destroy(struct zcomp *comp);
>  
> -struct zcomp_strm *zcomp_strm_find(struct zcomp *comp);
> +struct zcomp_strm *zcomp_strm_find(struct zcomp *comp, bool decomp);
>  void zcomp_strm_release(struct zcomp *comp, struct zcomp_strm *zstrm);
>  
>  int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index b3044d3..8283bd3 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -623,7 +623,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
>  		/* Use  a temporary buffer to decompress the page */
>  		uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
>  
> -	zstrm = zcomp_strm_find(zram->comp);
> +	zstrm = zcomp_strm_find(zram->comp, true);

No, I don't like this.

>  	user_mem = kmap_atomic(page);
>  	if (!is_partial_io(bvec))
>  		uncmem = user_mem;
> @@ -647,7 +647,8 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
>  	ret = 0;
>  out_cleanup:
>  	kunmap_atomic(user_mem);
> -	zcomp_strm_release(zram->comp, zstrm);
> +	if (zstrm)
> +		zcomp_strm_release(zram->comp, zstrm);
>  	if (is_partial_io(bvec))
>  		kfree(uncmem);
>  	return ret;
> @@ -676,14 +677,14 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  			ret = -ENOMEM;
>  			goto out;
>  		}
> -		zstrm = zcomp_strm_find(zram->comp);
> +		zstrm = zcomp_strm_find(zram->comp, true);
>  		ret = zram_decompress_page(zram, zstrm, uncmem, index);
>  		if (ret)
>  			goto out;
>  	}
>  
>  	if (!zstrm)
> -		zstrm = zcomp_strm_find(zram->comp);
> +		zstrm = zcomp_strm_find(zram->comp, false);

No. I don't like this.

	-ss
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