On (08/25/17 01:35), Nick Terrell wrote:
> On 8/24/17, 5:49 PM, "Joonsoo Kim" <iamjoonsoo....@lge.com> wrote:
> > On Thu, Aug 24, 2017 at 09:33:54PM +0000, Nick Terrell wrote:
> > > On Thu, Aug 24, 2017 at 10:49:36AM +0900, Sergey Senozhatsky wrote:
> > > > Add ZSTD to the list of supported compression algorithms.
> > > >
> > > > Official benchmarks [1]:
> > >
> > > Awesome! Let me know if you need anything from me.
> > >
> > Hello, Nick.
> >
> > Awesome work!!!
> >
> > Let me ask a question.
> > Zram compress and decompress a small data (a page) and your github
> > site says that using predefined dictionary would be helpful in this
> > situation. However, it seems that compression crypto API for zstd
> > doesn't use ZSTD_compress_usingDict(). Is there any plan to support
> > it?
excellent question, Joonsoo.
> 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'.
> What data have you, or anyone, used for benchmarking compression ratio and
> speed for RAM? Since it is such a specialized application, the standard
> compression benchmarks aren't very applicable.
yeah, I thought that zstd uses dicts unconditionally.
I used my own simple minded test script:
https://github.com/sergey-senozhatsky/zram-perf-test
it basically invokes fio with a 'static compression buffer', because
we want to have the exactly same data to be compressed when I compare
algorithms... I guess I need to improve it, somehow.
-ss
