Trond, do you happen to have any patches regarding the rewrite you mention below? We would love to test them or help in anyway we can. Thanks, Malahal. >> On Tue, Apr 12, 2011 at 11:49:29AM -0400, Trond Myklebust wrote: >> >> What is the exact plan? Split the direct I/O into two passes, one >> to lock down the user pages and then a second one to send the pages >> over the wire, which is shared with the writeback code? If that's >> the case it should naturally allow plugging in a scheme like Badari >> to send pages from different iovecs in a single on the wire request - >> after all page cache pages are non-continuous in virtual and physical >> memory, too. > >You can't lock the user pages unfortunately: they may need to be faulted >in. > >What I was thinking of doing is splitting out the code in the RPC >callbacks that plays around with page flags and puts the pages on the >inode's dirty list so that they don't get called in the case of >O_DIRECT. >I then want to attach the O_DIRECT pages to the nfsi->nfs_page_tree >radix tree so that they can be tracked by the NFS layer. I'm assuming >that nobody is going to be silly enough to require simultaneous writes >via O_DIRECT to the same locations. >Then we can feed the O_DIRECT pages into nfs_page_async_flush() so that >they share the existing page cache write coalescing and pnfs code. > >The commit code will be easy to reuse too, since the requests are listed >in the radix tree and so nfs_scan_list() can find and process them in >the usual fashion. > >The main problem that I have yet to figure out is what to do if the >server flags a reboot and the requests need to be resent. One option I'm >looking into is using the aio 'kick handler' to resubmit the writes. >Another may be to just resend directly from the nfsiod work queue. > >> When do you plan to release your read/write code re-write? If it's >> not anytime soon how is applying Badari's patch going to hurt? Most >> of it probably will get reverted with a complete rewrite, but at least >> the logic to check which direct I/O iovecs can coalesced would stay >> in the new world order. > >I'm hoping that I can do the rewrite fairly quickly once the resend >problem is solved. It shouldn't be more than a couple of weeks of >coding. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
