Rami, While I can pass the O_DIRECT flag to the flip_open, it seems that flip- >read and flip->write requires me to map the target pages as user pages. (get_user_pages ?) I'm trying to find ways to cut through the overhead as much as I can. In general, I want to be able to control my own caching; maintaining certain pages while dropping others.
Gilboa On Tue, 2005-08-30 at 04:00 -0400, Rami Rosen wrote: > Hello, > > I am not sure because I did not try it myself , but how about > simply opening it with O_DIRECT flag? > And BTW, how do you open the file in the kernel ? > did you use the sys_open() as was suggested in GergKH article I had > cited in > the thread from a month ago ? ( sys_open() accpets the O_DIRECT flag) > > Regards,, > Rami > > On 8/29/05, Gilboa Davara <[EMAIL PROTECTED]> wrote: > Hello all, > > Couple of weeks ago I started a thread called "File I/O within > kernel > threads?" which ended with a call "for numbers". (Read: Is I/O > within > kernel performance increase justifies the development > overhead?) > Last week I took my user-land simulator (that takes a file, > reads it, > and creates and sends two raw multiplexed streams out of it); > and > converted it into a kernel module. > The performance increase was nothing short of staggering: From > ~1100Mbps > to ~1700Mbps. (Which is fairly close to the theoretical limit > of 2 GbE > NICs.) > While both versions could be further optimized, it's clear > that the > kernel version has an very impressive performance lead. > Considering these numbers, I opt to choose a Kernel mode > solution. > > My question is simple: > While it's fairly easy to do normal buffered I/O from kernel > mode (using > flip_open/close and ->read/->write methods) for the life of me > I cannot > seem to find how to do O_DIRECT I/O from kernel mode. > More-ever, as I need a single huge file on a dedicated > computer, I don't > really need the FS/VFA/pagecache over-head, AFAIC I rather do > raw I/O > directly on-to the target block device. > Can anyone point me into the right direction? > > I'm currently trying to drill down the kernel source but it's > a daunting > task, to say the least. > > Again, I fully understand the implications of my request; I > understand > that I'm bending Linux sideways, etc. > > Gilboa > > > ================================================================= > To unsubscribe, send mail to [EMAIL PROTECTED] > with > the word "unsubscribe" in the message body, e.g., run the > command > echo unsubscribe | mail [EMAIL PROTECTED] > ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
