linux-kernel - RE: [RFC PATCH v1 01/13] crypto: acomp - Add a poll() operation to acomp_alg and acomp

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Message-ID: <SJ0PR11MB5678CE94DDBDEC00EA693293C9402@SJ0PR11MB5678.namprd11.prod.outlook.com>
Date: Fri, 18 Oct 2024 23:01:10 +0000
From: "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>
To: Herbert Xu <herbert@...dor.apana.org.au>
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	"Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>
Subject: RE: [RFC PATCH v1 01/13] crypto: acomp - Add a poll() operation to
 acomp_alg and acomp_req

Hi Herbert,

> -----Original Message-----
> From: Herbert Xu <herbert@...dor.apana.org.au>
> Sent: Friday, October 18, 2024 12:55 AM
> To: Sridhar, Kanchana P <kanchana.p.sridhar@...el.com>
> Cc: linux-kernel@...r.kernel.org; linux-mm@...ck.org;
> hannes@...xchg.org; yosryahmed@...gle.com; nphamcs@...il.com;
> chengming.zhou@...ux.dev; usamaarif642@...il.com;
> ryan.roberts@....com; Huang, Ying <ying.huang@...el.com>;
> 21cnbao@...il.com; akpm@...ux-foundation.org; linux-
> crypto@...r.kernel.org; davem@...emloft.net; clabbe@...libre.com;
> ardb@...nel.org; ebiggers@...gle.com; surenb@...gle.com; Accardi,
> Kristen C <kristen.c.accardi@...el.com>; zanussi@...nel.org;
> viro@...iv.linux.org.uk; brauner@...nel.org; jack@...e.cz;
> mcgrof@...nel.org; kees@...nel.org; joel.granados@...nel.org;
> bfoster@...hat.com; willy@...radead.org; linux-fsdevel@...r.kernel.org;
> Feghali, Wajdi K <wajdi.k.feghali@...el.com>; Gopal, Vinodh
> <vinodh.gopal@...el.com>
> Subject: Re: [RFC PATCH v1 01/13] crypto: acomp - Add a poll() operation to
> acomp_alg and acomp_req
> 
> On Thu, Oct 17, 2024 at 11:40:49PM -0700, Kanchana P Sridhar wrote:
> > For async compress/decompress, provide a way for the caller to poll
> > for compress/decompress completion, rather than wait for an interrupt
> > to signal completion.
> >
> > Callers can submit a compress/decompress using crypto_acomp_compress
> > and decompress and rather than wait on a completion, call
> > crypto_acomp_poll() to check for completion.
> >
> > This is useful for hardware accelerators where the overhead of
> > interrupts and waiting for completions is too expensive.  Typically
> > the compress/decompress hw operations complete very quickly and in the
> > vast majority of cases, adding the overhead of interrupt handling and
> > waiting for completions simply adds unnecessary delays and cancels the
> > gains of using the hw acceleration.
> >
> > Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> > Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
> > ---
> >  crypto/acompress.c                  |  1 +
> >  include/crypto/acompress.h          | 18 ++++++++++++++++++
> >  include/crypto/internal/acompress.h |  1 +
> >  3 files changed, 20 insertions(+)
> 
> How about just adding a request flag that tells the driver to
> make the request synchronous if possible?
> 
> Something like
> 
> #define CRYPTO_ACOMP_REQ_POLL	0x00000001

Thanks for your code review comments. Are you referring to how the
async/poll interface is enabled at the level of say zswap (by setting a
flag in the acomp_req), followed by the iaa_crypto driver testing for
the flag and submitting the request and returning -EINPROGRESS.
Wouldn't we still need a separate API to do the polling?

I am not the expert on this, and would like to request Kristen's inputs
on whether this is feasible.

Thanks,
Kanchana


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