Re: ext4 performance falloff

2014-04-08 Thread Dave Chinner
On Mon, Apr 07, 2014 at 09:40:28AM -0700, Andi Kleen wrote: > Jan Kara writes: > > > > What we really need is a counter where we can better estimate counts > > accumulated in the percpu part of it. As the counter approaches zero, it's > > CPU overhead will have to become that of a single locked va

Re: ext4 performance falloff

2014-04-07 Thread Jan Kara
On Mon 07-04-14 09:40:28, Andi Kleen wrote: > Jan Kara writes: > > > > What we really need is a counter where we can better estimate counts > > accumulated in the percpu part of it. As the counter approaches zero, it's > > CPU overhead will have to become that of a single locked variable but when

Re: ext4 performance falloff

2014-04-07 Thread Andi Kleen
Jan Kara writes: > > What we really need is a counter where we can better estimate counts > accumulated in the percpu part of it. As the counter approaches zero, it's > CPU overhead will have to become that of a single locked variable but when > the value of counter is relatively high, we want it

Re: ext4 performance falloff

2014-04-07 Thread Jan Kara
On Sat 05-04-14 11:28:17, Daniel J Blueman wrote: > On 04/05/2014 04:56 AM, Theodore Ts'o wrote: > >On Sat, Apr 05, 2014 at 01:00:55AM +0800, Daniel J Blueman wrote: > >>On a larger system 1728 cores/4.5TB memory and 3.13.9, I'm seeing very low > >>600KB/s cached write performance to a local ext4 f

Re: ext4 performance falloff

2014-04-04 Thread Daniel J Blueman
On 04/05/2014 04:56 AM, Theodore Ts'o wrote: On Sat, Apr 05, 2014 at 01:00:55AM +0800, Daniel J Blueman wrote: On a larger system 1728 cores/4.5TB memory and 3.13.9, I'm seeing very low 600KB/s cached write performance to a local ext4 filesystem: > Thanks for the heads up. Most (all?) of the

Re: ext4 performance falloff

2014-04-04 Thread Theodore Ts'o
On Sat, Apr 05, 2014 at 01:00:55AM +0800, Daniel J Blueman wrote: > On a larger system 1728 cores/4.5TB memory and 3.13.9, I'm seeing very low > 600KB/s cached write performance to a local ext4 filesystem: Hi Daniel, Thanks for the heads up. Most (all?) of the ext4 don't have systems with thousa

ext4 performance falloff

2014-04-04 Thread Daniel J Blueman
On a larger system 1728 cores/4.5TB memory and 3.13.9, I'm seeing very low 600KB/s cached write performance to a local ext4 filesystem: # mkfs.ext4 /dev/sda5 # mount /dev/sda5 /mnt # dd if=/dev/zero of=/mnt/test bs=1M count=10 10+0 records in 10+0 records out 10485760 bytes (10 MB) copied, 17.43