From: David Miller <davem@davemloft.net>
To: James.Bottomley@HansenPartnership.com
Cc: florian@mickler.org, awalls@md.metrocast.net,
mchehab@infradead.org, linux-media@vger.kernel.org,
linux-kernel@vger.kernel.org, js@linuxtv.org, tskd2@yahoo.co.jp,
liplianin@me.by, g.marco@freenet.de, aet@rasterburn.org,
pb@linuxtv.org, mkrufky@linuxtv.org, nick@nick-andrew.net,
max@veneto.com, janne-dvb@grunau.be, oliver@neukum.org,
greg@kroah.com, rjw@sisk.pl, joerg.roedel@amd.com
Subject: Re: [PATCH 0/6] get rid of on-stack dma buffers
Date: Tue, 22 Mar 2011 13:15:52 -0700 (PDT) [thread overview]
Message-ID: <20110322.131552.104076400.davem@davemloft.net> (raw)
In-Reply-To: <1300800904.3290.7.camel@mulgrave.site>
From: James Bottomley <James.Bottomley@HansenPartnership.com>
Date: Tue, 22 Mar 2011 08:35:04 -0500
> The API will round up so that the correct region covers the API.
> However, if you have other structures packed into the space (as very
> often happens on stack), you get cache line interference in the CPU if
> they get accessed: The act of accessing an adjacent object pulls in
> cache above your object and destroys DMA coherence. This is the
> principle reason why DMA to stack is a bad idea.
Another major real reason we can't DMA on-stack stuff is because the
stack is mapped virtually on some platforms.
And that is the original reason the restriction was put in place.
prev parent reply other threads:[~2011-03-22 20:15 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-21 18:33 [PATCH 0/6] get rid of on-stack dma buffers Florian Mickler
2011-03-21 18:33 ` [PATCH 1/6] [media] a800: " Florian Mickler
2011-03-21 18:33 ` [PATCH 2/6 v2] [media] vp7045: " Florian Mickler
2011-03-21 18:33 ` [PATCH 3/6] [media] friio: " Florian Mickler
2011-03-21 18:33 ` [PATCH 4/6] [media] dw2102: get rid of on-stack dma buffer Florian Mickler
2011-03-21 18:33 ` [PATCH 5/6] [media] m920x: get rid of on-stack dma buffers Florian Mickler
2011-03-21 18:33 ` [PATCH 6/6] [media] opera1: get rid of on-stack dma buffer Florian Mickler
2011-03-21 19:26 ` [PATCH 0/6] get rid of on-stack dma buffers Andy Walls
2011-03-21 21:03 ` Florian Mickler
2011-03-22 10:44 ` Roedel, Joerg
[not found] ` <AANLkTimXobrwc-XHgoVN1dD5NCTde64dykbyvtJMo229@mail.gmail.com>
2011-03-22 13:12 ` Oliver Neukum
2011-03-22 14:27 ` Florian Mickler
2011-03-22 10:59 ` Jiri Kosina
2011-03-22 12:33 ` Johannes Stezenbach
2011-03-22 13:35 ` James Bottomley
2011-03-22 14:02 ` Florian Mickler
2011-03-22 20:15 ` David Miller [this message]
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