Messages in this thread | | | Date | Mon, 17 Oct 2005 01:58:08 -0700 (PDT) | From | li nux <> | Subject | Re: A problem about DIRECT IO on ext3 |
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--- li nux <lnxluv@yahoo.com> wrote:
> > > --- Jens Axboe <axboe@suse.de> wrote: > > > On Mon, Aug 29 2005, Erik Mouw wrote: > > > There are four prerequisites for direct IO: > > > - the file needs to be opened with O_DIRECT > > > - the buffer needs to be page aligned (hint: use > > getpagesize() instead > > > of assuming that a page is 4k > > > - reads and writes need to happen *in* multiples > > of the soft block size > > > - reads and writes need to happen *at* multiples > > of the soft block size > > > > Actually, the buffer only needs to be hard block > > size aligned, same goes > > for the chunk size used for reads/writes. > > > > -- > > Jens Axboe > > On 2.4 the open call succeeds with O_DIRECT but read returns -EINVAL for any block size (512, 1024 ..16384) open("/tmp/midstress_idx10", O_RDWR|O_CREAT|O_DIRECT|O_LARGEFILE, 01001101270) = 3 read(3, 0xbfffdc40, 16384) = -1 EINVAL (Invalid argument) how to correct this problem ?
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