Re: [PATCH] zram: introduce per-device debug_stat sysfs node

[Sergey Senozhatsky]

On (05/13/16 15:23), Minchan Kim wrote:
[..]
> @@ -737,12 +737,12 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  		zcomp_strm_release(zram->comp, zstrm);
>  		zstrm = NULL;
>  
> -		atomic64_inc(&zram->stats.num_recompress);
> -
>  		handle = zs_malloc(meta->mem_pool, clen,
>  				GFP_NOIO | __GFP_HIGHMEM);
> -		if (handle)
> +		if (handle) {
> +			atomic64_inc(&zram->stats.num_recompress);
>  			goto compress_again;
> +		}

not like a real concern...

the main (and only) purpose of num_recompress is to match performance
slowdowns and failed fast write paths (when the first zs_malloc() fails).
this matching is depending on successful second zs_malloc(), but if it's
also unsuccessful we would only increase failed_writes; w/o increasing
the failed fast write counter, while we actually would have failed fast
write and extra zs_malloc() [unaccounted in this case]. yet it's probably
a bit unlikely to happen, but still. well, just saying.

	-ss