From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Williams Subject: Re: [PATCH 06/13] async_tx: add support for asynchronous GF multiplication Date: Sat, 21 Mar 2009 08:19:26 -0700 Message-ID: References: <20090318191248.20375.40560.stgit@dwillia2-linux.ch.intel.com> <20090318192046.20375.89854.stgit@dwillia2-linux.ch.intel.com> <49C26D91.10804@intel.com> <49C41C1E.4060401@zytor.com> <49C4201A.5060905@emcraft.com> <49C425F5.8060309@intel.com> <49C42F99.5010700@emcraft.com> <49C45159.8020503@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <49C45159.8020503@zytor.com> Sender: linux-kernel-owner@vger.kernel.org To: "H. Peter Anvin" Cc: Ilya Yanok , "H. Peter Anvin" , "linux-raid@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "neilb@suse.de" , "Sosnowski, Maciej" , Yuri Tikhonov List-Id: linux-raid.ids On Fri, Mar 20, 2009 at 7:30 PM, H. Peter Anvin wrote: > Ilya Yanok wrote: >> >> async_gen_syndrome() takes element of GF^n(256) and returns result o= f >> scalar multiplication of it with constant ({01}, {02}, {02}^2, ..., >> {02}^n) vector. > > For any n (which would mean any GF field)? =A0In that case, that is > generic scalar-vector multiplication... > >> async_pq() takes two vectors from GF^n(256) and returns their scalar >> multiplication. >> >> We need async_pq() function if we want to offload D_x =3D A * (P + P= _{xy}) >> + B * (Q + Q_{xy}) part of DD recovery and D_x =3D (Q + Q_x) * g^{-x= } part >> of DP recovery. > > > No, you don't. =A0A and B (and g^{-x}) are scalars, meaning they're t= he > same for every element. =A0This is simpler to do. Understood. However this routine also needs to cover the non-generic and non-constant case where we have a separate coefficient per element. I suppose it could scan the coefficient list to see if it can bypass the 2-dimensional lookup multiply. At the very least we need something like the following, because async_pq is really only a helper routine for async_r6recov.c which knows how to avoid the synchronous path. diff --git a/crypto/async_tx/async_pq.c b/crypto/async_tx/async_pq.c index da47a29..c1087a2 100644 --- a/crypto/async_tx/async_pq.c +++ b/crypto/async_tx/async_pq.c @@ -236,6 +236,7 @@ async_pq(struct page **blocks, unsigned int offset, int src_cnt, flags, depend_tx, cb_fn, cb_param); } else { /* run pq synchronously */ + WARN_ONCE(1, "INFO: async_pq entered synchronous path\n= "); if (!blocks[src_cnt+1]) { /* only p requested, just xor= */ flags |=3D ASYNC_TX_XOR_ZERO_DST; return async_xor(blocks[src_cnt], blocks, offse= t, @@ -252,7 +253,6 @@ async_pq(struct page **blocks, unsigned int offset, int src_cnt, return tx; } -EXPORT_SYMBOL_GPL(async_pq); Looking closer, the only other caller, async_pq_zero_sum, can be deleted because it has no users. So async_pq can become a static routine in async_r6recov. Thanks, Dan