Messages in this thread | | | Date | Thu, 8 Apr 2004 18:42:44 -0700 | From | Wim Coekaerts <> | Subject | Re: dd PATCH: add conv=direct |
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philip copeland did a whole set of patches for coreutils to allow directio for both read write and mixed sizes even the rpm is at http://oss.oracle.com/projects/ocfs/files/source/RHAT/RHAS3/coreutils-4.5.3-33.src.rpm, I think he took it up with the maintainers but so far had no luck
it makes sense to have this stuff, we use it a lot.
Wim
On Fri, Apr 09, 2004 at 10:37:37AM +1000, Anton Blanchard wrote: > > Hi, > > > OK, I can see that one. But it seems like a pretty small benefit to me > > -- CPU utilization is already really low. > > Maybe not to you but it does make a big difference on our 500 disk setup. > At the moment we use dd to do an initial sniff, then ext3 utils to do > O_DIRECT reads/writes. With O_DIRECT read/write in dd we could use it > instead. (We are basically interested in IO performance that a database > would see). > > > Um, that sounds like a bad idea to me. It seems to me it's the kernel's > > responsibility to figure out "hey, looks like a streaming read - let's > > not blow out the buffer cache trying to hold 20GB on a 512M system." If > > you're saying that the kernel guys have given up and the established > > wisdom is now "you gotta use O_DIRECT if you don't want to throw > > everything else out due to streaming data", well... I'm disappointed. > > When you start hitting memory bandwidth limits, O_DIRECT will help you. > Sure it wont be an issue for your dd copy scenario, but I wanted to point > out there are other valid uses for it. > > Anton > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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