From: "David S. Miller" <davem@redhat.com>
To: adam@yggdrasil.com
Cc: linux-kernel@vger.kernel.org
Subject: Re: Does pci_alloc_consisent really need to zero memory?
Date: Thu, 30 May 2002 02:49:59 -0700 (PDT) [thread overview]
Message-ID: <20020530.024959.65186398.davem@redhat.com> (raw)
In-Reply-To: <200205300911.CAA01655@adam.yggdrasil.com>
From: "Adam J. Richter" <adam@yggdrasil.com>
Date: Thu, 30 May 2002 02:11:12 -0700
Is it really necessary for pci_alloc_consistent() to
fill the memory that it returns with all zeroes? I don't
see anything in Documentation/DMA-mapping.txt that specifies
it. I have been on the lookout for drivers that rely on it
for the past couple of months, and I haven't seen any. It's
only one line of code in arch/i386/kernel/pci-dma.c, but it
is potentially a lot of cycles, even if only zeroes the
space you requested (rather than the full pages that it
actually allocates).
pci_alloc_consistent is so rare, I doubt it matters performance
wise.
I'd rather see a patch to DMA-mapping.txt that specifies the memory
returned is zeroed out, as this is what every implementation appears
to do.
next prev parent reply other threads:[~2002-05-30 10:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-05-30 9:11 Does pci_alloc_consisent really need to zero memory? Adam J. Richter
2002-05-30 9:49 ` David S. Miller [this message]
2002-05-30 11:05 ` Emmanuel Michon
2002-05-30 10:54 ` David S. Miller
-- strict thread matches above, loose matches on Subject: below --
2002-05-30 11:41 Adam J. Richter
2002-05-30 11:30 ` David S. Miller
2002-06-03 16:45 ` Pavel Machek
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