Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
As it turns out, I did a little rgreping in the source and it seems like I found a way to disable disk-barrier and disk-flushes in drbd 8.4.1. In drbd/drbd_receiver.c, the write ordering method seems like it's determined in the drbd_bump_write_ordering function. Inside the idr_for_each_entry loop I hard coded wo = WO_drain_io. I compiled the kernel module and tested it and it showed 'wo:d' like it should. As predicted the dd latency test went way down, but so did the throughput test. I think I'll probably just stick with barrier and take the latency hit, but I thought I'd post this in case anyone else wants to fool around with this setting. Chris On Mon, Apr 2, 2012 at 7:55 AM, Chris Dickson <chrisd1100 at gmail.com> wrote: > Interesting, I'm starting to think that a lot of these performance issues > people are seeing with 8.4.1 are related to this feature. I remember when > tweaking in 8.3 turning off flushes improved latency dramatically. > > I wonder if there is a patch for the source out there? Maybe I'll consult > the dev list to locate the spot in the code where this decision gets made > and hard code turning off barrier and flushes. > > > On Mon, Apr 2, 2012 at 2:26 AM, Christian Balzer <chibi at gol.com> wrote: > >> >> Hello, >> >> On Sat, 31 Mar 2012 11:42:33 -0400 Chris Dickson wrote: >> >> > It seems that ever since I upgraded to drbd 8.4.1 the 'disk-barrier no;' >> > and 'disk-flushes no;' options are not being respected in my resource >> > configuration file. A 'cat /proc/drbd' shows 'wo:b' regardless of what >> > options I set in the resource config. I also tried to set these via the >> > command line with drbdsetup to no avail. >> > >> > Anyone else seeing this issue and are there any known workarounds? >> > >> I can confirm that. Saw the same thing setting up my latest DRBD cluster >> here and promptly moved to 8.3.12, which fixed this and a slew of other >> problems and performance issues. >> >> Regards, >> >> Christian >> -- >> Christian Balzer Network/Systems Engineer >> chibi at gol.com Global OnLine Japan/Fusion Communications >> http://www.gol.com/ >> _______________________________________________ >> drbd-user mailing list >> drbd-user at lists.linbit.com >> http://lists.linbit.com/mailman/listinfo/drbd-user >> > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20120402/6cb06438/attachment.htm>