Date: Thu, 31 May 2007 21:47:08 -0700 From: "Matthew Jacob" <lydianconcepts@gmail.com> To: "Hidetoshi Shimokawa" <simokawa@freebsd.org> Cc: freebsd-scsi@freebsd.org Subject: Re: scsi_target with multiple luns Message-ID: <7579f7fb0705312147p60255cf2r9eac5d5eb8aa5236@mail.gmail.com> In-Reply-To: <465F955E.7050103@samsco.org> References: <86tztspdil.wl%simokawa@FreeBSD.ORG> <465F955E.7050103@samsco.org>
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Remember that scsi_target is an example. A fine example, but an example. Having a single user process that can be shot and killed, no matter how multithreaded or AIO'd, is not necessarily the wisest choice for building a target device. On 5/31/07, Scott Long <scottl@samsco.org> wrote: > Hidetoshi Shimokawa wrote: > > I have not fully analyzed the problem but I'll describe it just for a note. > > I'd like to ask maintainers of scsi_target for further analysis. > > > > I experiance a problem with small number(1) of simq and multiple > > scsi_target(8) instances. > > > > As far as I understand, the following situation could occur under a fairly > > heavy load. > > > > 1. process A send a request -> cam send to sim > > 2. process B send a request -> blocked because the simq is full > > 3. the request of process A is finished (in the context of process A) > > 4. cam/scsi_target tries to send the request of process B. > > But the mapped memory is of process A, and scsi_target send wrong > > ccb to sim. > > > > Maybe, we should rewrite scsi_target in kernel space with GEOM support.. > > I'm unclear on how GEOM would fix this. Also, scsi targets aren't > always DA devices. I dedicated scsi_da_target device that is backed > by GEOM might be interesting, though. Even more interesting would be > a direct DMA method that required no KVA mappings for the data. > > Scott > > _______________________________________________ > freebsd-scsi@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-scsi > To unsubscribe, send any mail to "freebsd-scsi-unsubscribe@freebsd.org" >
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