[LU-15725] Client side Mdtest File Read Regression introduced with fix for LU-11623

• Type: Bug
• Resolution: Unresolved
• Priority: Major
• Affects Version/s: Lustre 2.13.0
• Severity: 3
• Assignee: Lai Siyao
• Reporter: Petros Koutoupis

Description

While testing 2.15 and comparing it to our 2.12 branch, I observed a noticeable file read regression on the client side and after doing a git bisect, I narrowed it down to the patch https://review.whamcloud.com/38763 "LU-11623 llite: hash just created files if lock allows".

After reverting the patch, my read performance was immediately restored but it was at the expense of the huge file stat boost.

File stats
Original (2.12 results): 399893
Before Revert (2.15): 683490 —> +73%
After Revert (2.15): 401637

File Reads
Original (2.12 results) 297644
Before Revert (2.15): 250536 —> -15%
After Revert (2.15): 295096

mdtest script:

#!/bin/bash


NODES=21
PPN=16
PROCS=$(( $NODES * $PPN ))
MDT_COUNT=1
PAUSED=120


# Unique directory #
srun -N $NODES --ntasks-per-node $PPN ~bloewe/benchmarks/ior-3.3.0-CentOS-8.2/install/bin/mdtest -v -i 5 -p $PAUSED -C -E -T -r -n $(( $MDT_COUNT * 1048576 / $PROCS )) -u -d /mnt/kjlmo13/pkoutoupis/mdt0/test.`date +"%Y%m%d.%H%M%S"` 2>&1 |& tee f_mdt0_0k_ost_uniq.out

srun -N $NODES --ntasks-per-node $PPN ~bloewe/benchmarks/ior-3.3.0-CentOS-8.2/install/bin/mdtest -v -i 5 -p $PAUSED -C -w 32768 -E -e 32768 -T -r -n $(( $MDT_COUNT * 1048576 / $PROCS )) -u -d /mnt/kjlmo13/pkoutoupis/mdt0/test.`date +"%Y%m%d.%H%M%S"` 2>&1 |& tee f_mdt0_32k_ost_uniq.out 

 

Issue Links

• is related to: LU-11623 Allow caching of open-created dentries