[lustre-discuss] Degraded read performance with Large Bulk IO (16MB RPC)

Fri Dec 13 08:43:02 PST 2019

I ran the latest command you provided and it does not show the parameter, like you see.    I can do screenshare. 

[opc at lustre-client-1 ~]$ df -h

Filesystem              Size  Used Avail Use% Mounted on

/dev/sda3                39G  2.5G   36G   7% /

devtmpfs                158G     0  158G   0% /dev

tmpfs                   158G     0  158G   0% /dev/shm

tmpfs                   158G   17M  158G   1% /run

tmpfs                   158G     0  158G   0% /sys/fs/cgroup

/dev/sda1               512M   12M  501M   3% /boot/efi

10.0.3.6 at tcp1:/lfsbv     50T   89M   48T   1% /mnt/mdt_bv

10.0.3.6 at tcp1:/lfsnvme  185T  8.7M  176T   1% /mnt/mdt_nvme

tmpfs                    32G     0   32G   0% /run/user/1000

[opc at lustre-client-1 ~]$ lctl list_param -R llite | grep max_read_ahead

[opc at lustre-client-1 ~]$

So I ran this: 

[opc at lustre-client-1 ~]$ lctl list_param -R llite  >  llite_parameters.txt

There are other parameters under llite.   I attached the complete list. 

From: "Moreno Diego (ID SIS)" <diego.moreno at id.ethz.ch>
Date: Friday, December 13, 2019 at 8:36 AM
To: Pinkesh Valdria <pinkesh.valdria at oracle.com>, "lustre-discuss at lists.lustre.org" <lustre-discuss at lists.lustre.org>
Subject: Re: [lustre-discuss] Degraded read performance with Large Bulk IO (16MB RPC)

>From what I can see I think you just ran the wrong command (lctl list_param -R * ) or it doesn’t work as you expected on 2.12.3.

But llite params are sure there on a *mounted* Lustre client. 

This will give you the parameters you’re looking for and need to modify to have, likely, better read performance:

lctl list_param -R llite | grep max_read_ahead

From: Pinkesh Valdria <pinkesh.valdria at oracle.com>
Date: Friday, 13 December 2019 at 17:33
To: "Moreno Diego (ID SIS)" <diego.moreno at id.ethz.ch>, "lustre-discuss at lists.lustre.org" <lustre-discuss at lists.lustre.org>
Subject: Re: [lustre-discuss] Degraded read performance with Large Bulk IO (16MB RPC)

This is how I installed lustre clients (only showing packages installed steps). 

cat > /etc/yum.repos.d/lustre.repo << EOF

[hpddLustreserver]

name=CentOS- - Lustre

baseurl=https://downloads.whamcloud.com/public/lustre/latest-release/el7/server/

gpgcheck=0

[e2fsprogs]

name=CentOS- - Ldiskfs

baseurl=https://downloads.whamcloud.com/public/e2fsprogs/latest/el7/

gpgcheck=0

[hpddLustreclient]

name=CentOS- - Lustre

baseurl=https://downloads.whamcloud.com/public/lustre/latest-release/el7/client/

gpgcheck=0

EOF

yum  install  lustre-client  -y

reboot

From: "Moreno Diego (ID SIS)" <diego.moreno at id.ethz.ch>
Date: Friday, December 13, 2019 at 2:55 AM
To: Pinkesh Valdria <pinkesh.valdria at oracle.com>, "lustre-discuss at lists.lustre.org" <lustre-discuss at lists.lustre.org>
Subject: Re: [lustre-discuss] Degraded read performance with Large Bulk IO (16MB RPC)

>From what I can see they exist on my 2.12.3 client node:

[root at rufus4 ~]# lctl list_param -R llite | grep max_read_ahead

llite.reprofs-ffff9f7c3b4a8800.max_read_ahead_mb

llite.reprofs-ffff9f7c3b4a8800.max_read_ahead_per_file_mb

llite.reprofs-ffff9f7c3b4a8800.max_read_ahead_whole_mb

Regards,

Diego

From: Pinkesh Valdria <pinkesh.valdria at oracle.com>
Date: Wednesday, 11 December 2019 at 17:46
To: "Moreno Diego (ID SIS)" <diego.moreno at id.ethz.ch>, "lustre-discuss at lists.lustre.org" <lustre-discuss at lists.lustre.org>
Subject: Re: [lustre-discuss] Degraded read performance with Large Bulk IO (16MB RPC)

I was not able to find those parameters on my client nodes,  OSS or MGS nodes.   Here is how I was extracting all parameters .  

mkdir -p lctl_list_param_R/

cd lctl_list_param_R/

lctl list_param -R *  > lctl_list_param_R

[opc at lustre-client-1 lctl_list_param_R]$ less lctl_list_param_R  | grep ahead

llite.lfsbv-ffff98231c3bc000.statahead_agl

llite.lfsbv-ffff98231c3bc000.statahead_max

llite.lfsbv-ffff98231c3bc000.statahead_running_max

llite.lfsnvme-ffff98232c30e000.statahead_agl

llite.lfsnvme-ffff98232c30e000.statahead_max

llite.lfsnvme-ffff98232c30e000.statahead_running_max

[opc at lustre-client-1 lctl_list_param_R]$

I also tried these commands:  

Not working: 

On client nodes

lctl get_param llite.lfsbv-*.max_read_ahead_mb

error: get_param: param_path 'llite/lfsbv-*/max_read_ahead_mb': No such file or directory

[opc at lustre-client-1 lctl_list_param_R]$

Works 

On client nodes

lctl get_param llite.*.statahead_agl

llite.lfsbv-ffff98231c3bc000.statahead_agl=1

llite.lfsnvme-ffff98232c30e000.statahead_agl=1

[opc at lustre-client-1 lctl_list_param_R]$

From: "Moreno Diego (ID SIS)" <diego.moreno at id.ethz.ch>
Date: Tuesday, December 10, 2019 at 2:06 AM
To: Pinkesh Valdria <pinkesh.valdria at oracle.com>, "lustre-discuss at lists.lustre.org" <lustre-discuss at lists.lustre.org>
Subject: Re: [lustre-discuss] Degraded read performance with Large Bulk IO (16MB RPC)

With that kind of degradation performance on read I would immediately think on llite’s max_read_ahead parameters on the client. Specifically these 2:

max_read_ahead_mb: total amount of MB allocated for read ahead, usually quite low for bandwidth benchmarking purposes and when there’re several files per client

max_read_ahead_per_file_mb: the default is quite low for 16MB RPCs (only a few RPCs per file)

You probably need to check the effect increasing both of them.

Regards,

Diego

From: lustre-discuss <lustre-discuss-bounces at lists.lustre.org> on behalf of Pinkesh Valdria <pinkesh.valdria at oracle.com>
Date: Tuesday, 10 December 2019 at 09:40
To: "lustre-discuss at lists.lustre.org" <lustre-discuss at lists.lustre.org>
Subject: [lustre-discuss] Degraded read performance with Large Bulk IO (16MB RPC)

I was expecting better or same read performance with Large Bulk IO (16MB RPC),  but I see degradation in performance.   Do I need to tune any other parameter to benefit from Large Bulk IO?   Appreciate if I can get any pointers to troubleshoot further. 

Throughput before 

-          Read:  2563 MB/s

-          Write:  2585 MB/s

Throughput after

-          Read:  1527 MB/s. (down by ~1025)

-          Write:  2859 MB/s

Changes I did are: 

On oss

-          lctl set_param obdfilter.lfsbv-*.brw_size=16

On clients 

-          unmounted and remounted

-          lctl set_param osc.lfsbv-OST*.max_pages_per_rpc=4096  (got auto-updated after re-mount)

-          lctl set_param osc.*.max_rpcs_in_flight=64   (Had to manually increase this to 64,  since after re-mount, it was auto-set to 8,  but read/write performance was poor)

-          lctl set_param osc.*.max_dirty_mb=2040. (setting the value to 2048 was failing with : Numerical result out of range error.   Previously it was set to 2000 when I got good performance. 

My other settings: 

-          lnetctl net add --net tcp1 --if $interface  –peer-timeout 180 –peer-credits 128 –credits 1024

-          echo "options ksocklnd nscheds=10 sock_timeout=100 credits=2560 peer_credits=63 enable_irq_affinity=0"  >  /etc/modprobe.d/ksocklnd.conf

-          lfs setstripe -c 1 -S 1M /mnt/mdt_bv/test1

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