On Tue, May 22, 2007 at 11:21:20AM -0700, Andrew Morton wrote: > > > > I patched jbd's log_do_checkpoint to put all the blocks it wanted to > > write in a radix tree, then send them all down in order at the end. > > Side note: we already have all of that capability in the kernel: > sync_inode(blockdev_inode, wbc) will do an ascending-LBA write of the whole > blockdev. > > It could be that as a quick diddle, running sync_inode() in > do-block-on-queue-congestion mode prior to doing the checkpoint would have > some benefit.
I had played with this in the past (although not this time around), but I had performance problems with newly dirtied blocks sneaking in. > > At any rate, it may be worth putzing with the writeback routines to try > > and find dirty pages close by in the block dev inode when doing data > > writeback. My guess is that ext3 should be going 1.5x to 2x faster for > > this particular run, but that's a huge amount of complexity added so I'm > > not convinced it is a great idea. > > Yes, this is a distinct disadvantage of the whole per-address-space > writeback scheme - we're leaving IO scheduling optimisations on the floor, > especially wrt the blockdev inode, but probably also wrt regular-file > versus regular-file. Even if one makes the request queue tremendously > huge, that won't help if there's dirty data close-by the disk head which > hasn't even been put into the queue yet. > I'm not sure yet on a good way to fix it, but I do think I've nailed it down as the cause of the strange performance numbers I'm getting. -chris - 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/
