On Tue, 2005-03-01 at 13:37, Arjan van de Ven wrote: > On Tue, 2005-03-01 at 10:24 -0800, Bryan Henderson wrote: > > One thing that's implicit in your reasons for wanting to be in the kernel > > is that you've chosen to exploit the kernel's page cache. As a user of > > the page cache, you have more control from inside the kernel than from > > user space. The page cache was designed to be fundamentally invisible to > > user space. > > > > A pure user space implementation of an ISCSI target would use process > > virtual memory for a cache and manage it itself. It would access the > > storage with direct I/O. > > why would it use direct I/O ? Direct I/O would be really stupid for such > a thing to use since that means there's no caching going on *at all*. > what Bryan suggest is a privately owned and managed user space cache. so for that disk write should be real write-through.
it is hard to beat linux kernel cache performance though. > You want to *use* the kernel pagecache as much as you can. You do so by > using mmap and such, and msync to force content to disk. That uses the > kernel pagecache to the maximum extend, while not having to bother with > knowing the intimate details of the implementation thereof, which a > kernel side implementation would be involved in. (if it wasnt and only > used highlevel functions, then you might as well do the same in > userspace after all) > > - > 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 - 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
