Alfred Perlstein wrote:
> * Joy Ganguly <[EMAIL PROTECTED]> [000517 09:41] wrote:
> >
> > hi all,
> >
> > i have written a special ioctl which writes data into a file from a buffer in
> > kernel memory. it invokes fo->fo_write() and involves one copy from kernel
> > mem
> > to disk cache. however this takes substantially more time than an ordinary
> > write which copies from user space to the disk cache. any explanations???
>
> What are you using for your kernel to kernel copy?
>
fo->fo_write uses uiomove() with seg_flg = UIO_SYSSPACE. uiomove() uses
bcopy() to do the actual copying. my ioctl sets up the struct uio to point to the
kernel buf and calls fo->fo_write(). Hence the only difference between my ioctl
and original write is that the former has seg_flg = UIO_SYSSPACE and the latter
has UIO_USERSPACE.
>
> (copyin and friends are hand optimized for great speed when copying
> from/to userspace)
>
what sort of optimizations are you referrring to?? is there some other way i can
do this??
>
> --
> -Alfred Perlstein - [[EMAIL PROTECTED]|[EMAIL PROTECTED]]
> "I have the heart of a child; I keep it in a jar on my desk."
>
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