From: Manfred Spraul <manfred@colorfullife.com>
To: Russell King <rmk@arm.linux.org.uk>
Cc: Johannes Erdfelt <johannes@erdfelt.com>, linux-kernel@vger.kernel.org
Subject: Re: Inefficient PCI DMA usage (was: [experimental patch] UHCI updates)
Date: Sun, 21 Jan 2001 09:36:42 +0100 [thread overview]
Message-ID: <3A6A9F9A.3CDE1B05@colorfullife.com> (raw)
In-Reply-To: <200101202315.f0KNFTV01790@flint.arm.linux.org.uk>
Russell King wrote:
>
> Johannes Erdfelt writes:
> > They need to be visible via DMA. They need to be 16 byte aligned. We
> > also have QH's which have similar requirements, but we don't use as many
> > of them.
>
> Can we get away from the "16 byte aligned" and make it "n byte aligned"?
> I believe that slab already has support for this?
>
Not yet, but that would be a 2 line patch (currently it's hardcoded to
BYTES_PER_WORD align or L1_CACHE_BYTES, depending on the HWCACHE_ALIGN
flag).
But there are 2 other problems:
* kmem_cache_alloc returns one pointer, pci_alloc_consistent 2 pointers:
one dma address, one virtual address.
* The code relies on the virt_to_page() macro.
The second problem is the difficult one, I don't see how I could remove
that dependency without a major overhaul.
--
Manfred
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next prev parent reply other threads:[~2001-01-21 8:37 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-01-20 18:00 Manfred Spraul
2001-01-20 18:08 ` Johannes Erdfelt
2001-01-20 23:15 ` Russell King
2001-01-21 8:36 ` Manfred Spraul [this message]
2001-01-21 10:51 ` Russell King
2001-01-21 11:49 ` Manfred Spraul
2001-01-21 17:37 ` Johannes Erdfelt
2001-01-21 23:11 ` Russell King
[not found] <3A691043.F18CA6CA@megapathdsl.net>
2001-01-20 5:38 ` Johannes Erdfelt
2001-01-20 8:28 ` Russell King
2001-01-20 17:34 ` Johannes Erdfelt
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