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Date: Wed, 13 Mar 2013 15:03:55 +0400
From: Lev Serebryakov <lev@FreeBSD.org>
Organization: FreeBSD
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To: Konstantin Belousov <kostikbel@gmail.com>, arch@freebsd.org
Subject: Re: Unmapped buffers: to be merged in several days
In-Reply-To: <14310571813.20130313150228@serebryakov.spb.ru>
References: <20130311091852.GR3794@kib.kiev.ua> <86k3pe1cl3.fsf@ds4.des.no>
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Hello, Lev.
You wrote 13 =CD=C1=D2=D4=C1 2013 =C7., 15:02:28:

>>>  Will GEOM class, which needs to touch data (like raid3 or my off-tree
>>> raid5), benefit from conversion, compare to generic mechanism,
>>> provided for not-converted by your patch?
KB>> First, what do you mean by 'benefit'. Answer would obviously depend
KB>> on the criteria.
LS>  One more thought: it seems, that raid3/raid5 software implementations
LS> could benefit on reading when strict checks are disabled. Is it
LS> possible to map downstream BIOs, but use upstream ones unmapped?
 Where could I see documentation/examples how to:

  (a) manually map unmapped BIO
  (b) create unmapped BIO to pass downstream


--=20
// Black Lion AKA Lev Serebryakov <lev@FreeBSD.org>