linux-kernel - Re: [PATCH] zram: add zstd to the supported algorithms list

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170825022106.GC743@jagdpanzerIV.localdomain>
Date:   Fri, 25 Aug 2017 11:21:06 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Nick Terrell <terrelln@...com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "minchan@...nel.org" <minchan@...nel.org>,
        Yann Collet <cyan@...com>
Subject: Re: [PATCH] zram: add zstd to the supported algorithms list

On (08/25/17 02:09), Nick Terrell wrote:
[..]
> > > I think using dictionaries in zram could be very interesting. We could for
> > > example, take a random sample of the RAM and use that as the dictionary
> > > for compression. E.g. take 32 512B samples from RAM and build a 16 KB
> > > dictionary (sizes may vary).
> > > 
> > > I'm not sure how you would pass a dictionary into the crypto compression
> > > API, but I'm sure we can make something work if dictionary compression
> > > proves to be beneficial enough.
> > 
> > a dictionaty pointer can be in `struct zstd_ctx'.
> 
> Sorry I'm not super familiar with the crypto API. How would the user
> initialize the dictionary in the `struct zstd_ctx'? I guess you could
> either expose the struct in some header, or provide a function that
> initializes it, but that isn't generic. Does the crypto library already
> have a standard way to provide extra information?

not really familiar either... I was thinking about having "zstd" and
"zstd_dict" crypto_alg structs - one would be !dict, the other one would
allocate dict and pass it to compress/decompress zstd callbacks. "zstd"
vecrsion would invoke zstd_params() passing zeros as compress and dict
sizes to ZSTD_getParams(), while "zstd_dict" would invoke, lets say,
zstd_params_dict() passing PAGE_SIZE-s. hm... (0, PAGE_SIZE)?  to
ZSTD_getParams(). just a rough idea...

	-ss