On Thu, 11 Jan 2007, Linus Torvalds wrote: > On Thu, 11 Jan 2007, Viktor wrote: > > > > OK, madvise() used with mmap'ed file allows to have reads from a file > > with zero-copy between kernel/user buffers and don't pollute cache > > memory unnecessarily. But how about writes? How is to do zero-copy > > writes to a file and don't pollute cache memory without using O_DIRECT? > > Do I miss the appropriate interface? > > mmap()+msync() can do that too. > > Also, regular user-space page-aligned data could easily just be moved into > the page cache. We actually have a lot of the infrastructure for it. See > the "splice()" system call.
it seems to me that if splice and fadvise and related things are sufficient for userland to take care of things "properly" then O_DIRECT could be changed into splice/fadvise calls either by a library or in the kernel directly... looking at the splice(2) api it seems like it'll be difficult to implement O_DIRECT pread/pwrite from userland using splice... so there'd need to be some help there. i'm probably missing something. -dean - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
