then i run out of idea. i guess only evms developer can tell u exactly why 2.6 evms has such performance loss compared with 2.4.x both evms and lvm use device mapper in kernel and i do not see such performance loss in lvm. so pretty strange, ming On Wed, 2006-03-15 at 13:48 -0800, Ken Hwang wrote: > Hi Ming, > > I did blockdev --setra 1024 on kernel 2.6 system to make the same number as > read from kernel 2.4 and the result: > test:sync; time dd if=/dev/evms/volume1 of=/dev/null bs=1024k count=1024 > kernel 2.6 got 44.444s/0.004s/24.254s, and it was 46.690s/0.024s/26.902s. > It's still far away from kernel 2.4: 33.649s/0.010s/20.430s. > > > blockdev --setra 64 /dev/evms.nodes/md/md3 > test:sync; time dd if=/dev/evms/.nodes/md/md3 of=/dev/null bs=1024k > count=1024 > kernel 2.6 got 26.770s/0.016s/11.257s, and it was 23.763s/0.008s/16.097s. > The real time gets slower but system time gets faster. And they are still > not close to > kernel 2.4 19.471s/0.000s/13.480s > > Do you have any advice I can do to tune the 2.6 performance? > > Thanks in advance, > > Ken > > -----Original Message----- > From: Ming Zhang [mailto:mingz@xxxxxxxxxxx] > Sent: Saturday, March 11, 2006 3:17 PM > To: ken.hwang@xxxxxxxxx > Cc: device-mapper development > Subject: RE: 2.6 device mapper performance? > > > On Fri, 2006-03-10 at 21:58 -0800, Ken Hwang wrote: > > Hi Ming, > > > > I did more tests and list them at the following. Please help me analyze > them > > if it's possible and thanks. Allow me describe the disk/volume layout. I > had > > 4 120GB sata disks as sda, sdb, sdc, sdd. And they form 4 raid5 region, on > > top of the raid5 region there is a container, then I take 50% of the > > container to be a evms region, and then put a evms volume > /dev/evms/volume1 > > on top of the region. And I believe the raid5 region I used can be found > at > > /dev/evms/.nodes/md/md3. > > > > test: sync; time dd if=/dev/evms/volume1 of=/dev/null bs=1024k count=1024 > > kernel 2.4 got 33.649s/0.010s/20.430s (real/user/sys) > > kernel 2.6 got 46.690s/0.024s/26.902s > > > > test: sync; time dd if=/dev/evms/.nodes/md/md3 of=/dev/null bs=1024k > > count=1024 > > kernel 2.4: 19.471s/0.000s/13.480s > > kernel 2.6: 23.763s/0.008s/16.097s > > > > test: sync; time dd if=/dev/zero of=/dev/evms/volume1 bs=1024k count=1024 > > kernel 2.4: 69.183s/0.000s/15.430s > > krenel 2.6: 52.543s/0.004/7.640s > > > > test: sync; time dd if=/dev/zero of=/dev/evms/.nodes/md/md3 bs=1024k > > count=1024 > > kernel 2.4: 37.862s/0.000s/11.730s > > kernel 2.6: 23.628s/0.000s/5.536s > > > > test: blockdev --getra /dev/evms/volume1 > > kernel 2.4: 1024 > > kernel 2.6: 384 > > try to increase this number by --setra with blockdev > > > > > test: blockdev --getra /dev/evms/.nodes/md/md3 > > kernel 2.4: 64 > > kernel 2.6: 256 > > > > Looks like kernel 2.4 reading is faster than 2.6 but 2.6 writing is > faster. > > > > By comparing read from md3 and volume1, > > kernel 2.4 drop from 19.471s to 33.649s (72.8%) > > kernel 2.6 drop from 23.763s to 46.690s (96.4%) > > > > By comparing write to md3 and volume1, > > kernel 2.4 drop from 37.862s to 69.183s (82.7%) > > kernel 2.6 drop from 23.628s to 52.543s (122.4%) > > > > What's the blockdev numbers mean? > > yes, pretty big drop here. no idea why. i think both lvm and evms use dm > and should not have such big difference. > > that is to query/set the readahead buffer window, useful for sequential > workload. > > > > > > Thanks, > > > > Ken > > > > > > -----Original Message----- > > From: Ming Zhang [mailto:mingz@xxxxxxxxxxx] > > Sent: Friday, March 10, 2006 8:59 AM > > To: ken.hwang@xxxxxxxxx; device-mapper development > > Subject: Re: 2.6 device mapper performance? > > > > > > u have too many chances here. so hard to blame any one. suggest u to > > test it one by one if possible. > > > > for example, have same box run 2.4 and 2.6, test performance on volume > > first before run xfs, and samba. > > > > ming > > > > On Wed, 2006-03-08 at 16:49 -0800, Ken Hwang wrote: > > > Hi, > > > > > > I'm not sure I should ask this question here, if this is not the place > > then > > > I apologize. I have a home made NAS with Linux. I use evms to create > > volume, > > > put xfs on top of it, and then use samba to share it with Windows > clients. > > > When I was using kernel 2.4 with all the needed patches I could get > > netbench > > > 106Mbps with 4 clients, and 95Mbps with 8 clients. Recently I upgraded > the > > > same hardware to kernel 2.6 (I also upgraded the related application > such > > as > > > samba, xfs utility, and dmsetup accordingly). Then I ran netbench again > > and > > > got 80Mbps with 4 clients, 53Mbps with 8 clients. Which drop almost 80% > > (95 > > > vs 53) in 8 clients case. > > > > > > I then make and mount xfs on another raid5 (which uses the same disk > but > > on > > > different partitions) and found it got better performance (95Mbps with 4 > > > clients, 85Mbps with 8 clients). In brief: > > > xfs volume on raid5 md/md1 on sda6/sdb6/sdc6/sdd6 netbench: 95/85Mbps > > > xfs volume on EVMS volume /dev/evms/volume1 on raid5 md/md3 on > > > sda8/sdb8/sdc8/sdd8: 80/53Mbps > > > > > > Do you think the slow down (85 to 53Mbps) was caused by device mapper? > > > Please advice. > > > > > > Ken > > > > > > -- > > > No virus found in this outgoing message. > > > Checked by AVG Free Edition. > > > Version: 7.1.375 / Virus Database: 268.2.0/276 - Release Date: 3/7/2006 > > > > > > -- > > > > > > dm-devel@xxxxxxxxxx > > > https://www.redhat.com/mailman/listinfo/dm-devel > > -- > > No virus found in this incoming message. > > Checked by AVG Free Edition. > > Version: 7.1.375 / Virus Database: 268.2.1/278 - Release Date: 3/9/2006 > > > > -- > > No virus found in this outgoing message. > > Checked by AVG Free Edition. > > Version: 7.1.375 / Virus Database: 268.2.1/279 - Release Date: 3/10/2006 > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.375 / Virus Database: 268.2.1/279 - Release Date: 3/10/2006 > > -- > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.1.385 / Virus Database: 268.2.4/282 - Release Date: 3/15/2006 > -- dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
