From: Arjan van de Ven <[EMAIL PROTECTED]> Subject: [Iscsitarget-devel] Re: [ANNOUNCE] iSCSI enterprise target software Date: Tue, 01 Mar 2005 10:46:03 +0100
> fsync or msync() ? I would imagine the target mmaping it's backend in > userspace and using msync() to kick off IO. At which point it's not that > much different from the control you do of the pagecache from inside the > kernel... Can we avoid calling mmap() and munmap() repeatedly with large disk? > > When the target calls fsync(), dirty page cache is supposed to be > > committed to disk. However, the disk drive uses write-back policy, it > > is not. The data is still in disk drive cache. There is no system call > > to control disk drive cache. So the target (in the user space) cannot > > make good use of it. > > fsync() (and I suppose msync()) nowadays send a "flush cache" command to > the physical disk as well. This is new since 2.6.9 or so. > > > The current code also assumes the disk drive uses write-through > > policy. This is because no handy vfs interface for controlling disk > > drive cache. I think that there is some room for further improvement > > in the Linux kernel for storage systems. > > that's already present since 2.6.9..... Thanks a lot. I've not noticed these changes. I'll see the code later. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
