Messages in this thread | | | From | Denis Vlasenko <> | Subject | Re: AIO!! | Date | Tue, 11 Oct 2005 12:25:35 +0300 |
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On Tuesday 11 October 2005 08:04, Karthik Sarangan wrote: > > Benjamin LaHaise wrote: > > O_DIRECT buffers must be aligned on block sized boundaries (minimum 512 > > bytes). Check the actual return code from the aiocb and you'll find that > > it is likely -EINVAL, no -EINPROGRESS. See the man page for > > posix_memalign() to properly align the pointer. > > EEP!! I forgot all about buffer alignment!! Thanks for pointing it out
Why do you constantly shout?
> ------------------ > Two more questions. > > 1. Is aio_fsync of any use while 'aio_read'ing and 'aio_write'ing to > a 'raw' device or a '/dev/sdb' with O_DIRECT?
I suspect you did not do some research first.
> 2. I have an Ultra320 SCSI disk whose datasheet says it has a max. > possible throughput of 78MBps > > I did a 'aio_write' onto '/dev/sdb' with O_DIRECT. > Following are some throughput values. > > Buffer for IO | Avg Speed > (in KBytes) | > ----------------O----------- > Upto 512KB | 69MBps > 1024KB | 125MBps > 2048KB | 250MBps > 4096KB | 500MBps > 8192KB | 1GBps -- What the !! --
Most probably bug in your program.
> Buffer cache does not come into consideration. > > Does this mean that the SCSI lower layer (aic79xx) can transfer data > only upto 512 KB?
It means that you are in dire need of reading this:
http://www.catb.org/~esr/faqs/smart-questions.html
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