RE: [PATCH v4 01/10] crypto: acomp - Define two new interfaces for compress/decompress batching.

["Sridhar, Kanchana P" <kanchana.p.sridhar@intel.com>]

> -----Original Message-----
> From: Sridhar, Kanchana P <kanchana.p.sridhar@intel.com>
> Sent: Monday, November 25, 2024 6:37 PM
> To: Herbert Xu <herbert@gondor.apana.org.au>
> Cc: linux-kernel@vger.kernel.org; linux-mm@kvack.org;
> hannes@cmpxchg.org; yosryahmed@google.com; nphamcs@gmail.com;
> chengming.zhou@linux.dev; usamaarif642@gmail.com;
> ryan.roberts@arm.com; 21cnbao@gmail.com; akpm@linux-foundation.org;
> linux-crypto@vger.kernel.org; davem@davemloft.net; clabbe@baylibre.com;
> ardb@kernel.org; ebiggers@google.com; surenb@google.com; Accardi,
> Kristen C <kristen.c.accardi@intel.com>; Feghali, Wajdi K
> <wajdi.k.feghali@intel.com>; Gopal, Vinodh <vinodh.gopal@intel.com>;
> Sridhar, Kanchana P <kanchana.p.sridhar@intel.com>
> Subject: RE: [PATCH v4 01/10] crypto: acomp - Define two new interfaces for
> compress/decompress batching.
> 
> 
> > -----Original Message-----
> > From: Herbert Xu <herbert@gondor.apana.org.au>
> > Sent: Monday, November 25, 2024 6:14 PM
> > To: Sridhar, Kanchana P <kanchana.p.sridhar@intel.com>
> > Cc: linux-kernel@vger.kernel.org; linux-mm@kvack.org;
> > hannes@cmpxchg.org; yosryahmed@google.com; nphamcs@gmail.com;
> > chengming.zhou@linux.dev; usamaarif642@gmail.com;
> > ryan.roberts@arm.com; 21cnbao@gmail.com; akpm@linux-foundation.org;
> > linux-crypto@vger.kernel.org; davem@davemloft.net;
> clabbe@baylibre.com;
> > ardb@kernel.org; ebiggers@google.com; surenb@google.com; Accardi,
> > Kristen C <kristen.c.accardi@intel.com>; Feghali, Wajdi K
> > <wajdi.k.feghali@intel.com>; Gopal, Vinodh <vinodh.gopal@intel.com>
> > Subject: Re: [PATCH v4 01/10] crypto: acomp - Define two new interfaces
> for
> > compress/decompress batching.
> >
> > On Tue, Nov 26, 2024 at 02:13:00AM +0000, Sridhar, Kanchana P wrote:
> > >
> > > I wanted to make sure I understand your suggestion: Are you suggesting
> we
> > > implement request chaining for "struct acomp_req" similar to how this is
> > being
> > > done for "struct ahash_request" in your patch?
> > >
> > > I guess I was a bit confused by your comment about rebasing, which
> would
> > > imply a direct use of the request chaining API you've provided for "crypto
> > hash".
> > > I would appreciate it if you could clarify.
> >
> > Yes I was referring to the generic part of request chaining,
> > and not rebasing acomp on top of ahash.
> 
> Ok, thanks for the clarification! Would it be simpler if you could submit a
> crypto_acomp request chaining patch that I can then use in iaa_crypto?
> I would greatly appreciate this.

Hi Herbert,

I was able to take a more in-depth look at the request chaining you have
implemented in crypto ahash, and I think I have a good understanding of
what needs to be done in crypto acomp for request chaining. I will go ahead
and try to implement this and reach out if I have any questions. 

I would be interested to know the performance impact if we kept the
crypto_wait based chaining of the requests (which makes the request chaining
synchronous IIUC), wrt the asynchronous polling that's currently used for
batching in the iaa_crypto driver. If you have any ideas on introducing
polling to the chaining concept, please do share, I would greatly appreciate
it.

Besides this, some questions that came up as far as applying request chaining
to crypto_acomp_batch_[de]compress were:

1) It appears a calling module like zswap would only be able to get 1 error
     status for all the requests that are chained, as against individual error
     statuses for each of the [de]compress jobs. Is this understanding correct?
2) The request chaining makes use of the req->base.complete and req->base.data,
     which are also used for internal data by the iaa_crypto driver. I can add another
     "void *data1" member to struct crypto_async_request to work around this,
     such that iaa_crypto uses "data1" instead of "data".

Please let me know if you have any suggestions. Also, if you have already begun
working on acomp request chaining, just let me know. I will wait for your patch
in this case (rather than implementing it myself).

Thanks,
Kanchana


> 
> Thanks,
> Kanchana
> 
> 
> >
> > Cheers,
> > --
> > Email: Herbert Xu <herbert@gondor.apana.org.au>
> > Home Page: http://gondor.apana.org.au/~herbert/
> > PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt