[EMAIL PROTECTED] wrote:
In order to protect the user pages while a DIO is in progress, we want support from the VM that isn't presently implemented. To prevent a page from being accessed by another thread, we have to unmap the TLB/PTE entries and lock the page. There's a cost associated with this, as it may be necessary to cross-call other CPUs. Any thread that accesses the locked pages will block. While it's possible lock pages in the VM today, there isn't a neat set of interfaces the filesystem can use to maintain the integrity of the user's buffers. Without an experimental prototype to verify the design, it's impossible to say whether overhead of manipulating the page permissions is more than the cost of bypassing the cache.
Note also that for most applications, the size of their IO operations would often not match the current page size of the buffer, causing additional performance and scalability issues. - Bart -- Bart Smaalders Solaris Kernel Performance [EMAIL PROTECTED] http://blogs.sun.com/barts _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
