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Re: write alignment matters?
On Jun 23, 2011, at 4:41 AM, Thor Lancelot Simon wrote:
> On Thu, Jun 23, 2011 at 03:36:25PM +0700, Robert Elz wrote:
>> Date: Wed, 22 Jun 2011 19:30:55 -0400 (EDT)
>> From: der Mouse <mouse%Rodents-Montreal.ORG@localhost>
>> | But the interface is much older than that, and, even if it's not
>> | codified, there's a lot of history behind the notion that userland
>> | alignment of write() buffers affects, at most, performance, to the
>> | point where I consider it part of the interface.
>> Not on access to raw devices it isn't, and never was - what Erik Fair
>> said (Message-id:
>> was 100% correct - if you're using a raw device, it is up to the
>> application to meet whatever the requirements of that particular device
>> are, because one of the properties of raw devices is that they don't
>> do any kind of rebuffering of data (and the driver must not - that is
>> a part of the interface contract).
> That doesn't seem like it can really be right. There are plenty of
> systems where devices cannot DMA from user addresses.
Really? That seems unlikely.
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