Re: [PATCH v18 00/32] per memcg lru_lock

[Alex Shi]

在 2020/8/26 上午9:19, Daniel Jordan 写道:
> On Tue, Aug 25, 2020 at 11:26:58AM +0800, Alex Shi wrote:
>> 在 2020/8/25 上午9:56, Daniel Jordan 写道:
>>> Alex, do you have a pointer to the modified readtwice case?
>>
>> Sorry, no. my developer machine crashed, so I lost case my container and modified
>> case. I am struggling to get my container back from a account problematic repository. 
>>
>> But some testing scripts is here, generally, the original readtwice case will
>> run each of threads on each of cpus. The new case will run one container on each cpus,
>> and just run one readtwice thead in each of containers.
> 
> Ok, what you've sent so far gives me an idea of what you did.  My readtwice
> changes were similar, except I used the cgroup interface directly instead of
> docker and shared a filesystem between all the cgroups whereas it looks like
> you had one per memcg.  30 second runs on 5.9-rc2 and v18 gave 11% more data
> read with v18.  This was using 16 cgroups (32 dd tasks) on a 40 CPU, 2 socket
> machine.

I clean up my testing and make it reproducable by a Dockerfile and a case patch which
attached. 
User can build a container from the file, and then do testing like following:

#start some testing containers
for ((i=0; i< 80; i++)); do docker run --privileged=true --rm lrulock bash -c " sleep 20000" & done

#do testing evn setup 
for i in `docker ps | sed '1 d' | awk '{print $1 }'` ;do docker exec --privileged=true -it $i bash -c "cd vm-scalability/; bash -x ./case-lru-file-readtwice m"& done

#kick testing
for i in `docker ps | sed '1 d' | awk '{print $1 }'` ;do docker exec --privileged=true -it $i bash -c "cd vm-scalability/; bash -x ./case-lru-file-readtwice r"& done

#show result
for i in `docker ps | sed '1 d' | awk '{print $1 }'` ;do echo === $i ===; docker exec $i bash -c 'cat /tmp/vm-scalability-tmp/dd-output-* '  & done | grep MB | awk 'BEGIN {a=0;} { a+=$10 } END {print NR, a/(NR)}'

This time, on a 2P * 20 core * 2 HT machine,
This readtwice performance is 252% compare to v5.9-rc2 kernel. A good surprise!

> 
>>> Even better would be a description of the problem you're having in production
>>> with lru_lock.  We might be able to create at least a simulation of it to show
>>> what the expected improvement of your real workload is.
>>
>> we are using thousands memcgs in a machine, but as a simulation, I guess above case
>> could be helpful to show the problem.
> 
> Using thousands of memcgs to do what?  Any particulars about the type of
> workload?  Surely it's more complicated than page cache reads :)

Yes, the workload are quit different on different business, some use cpu a lot, some use
memory a lot, and some are may mixed. For containers number, that are also quit various
from tens to hundreds to thousands.

> 
>>> I ran a few benchmarks on v17 last week (sysbench oltp readonly, kerndevel from
>>> mmtests, a memcg-ized version of the readtwice case I cooked up) and then today
>>> discovered there's a chance I wasn't running the right kernels, so I'm redoing
>>> them on v18.
> 
> Neither kernel compile nor git checkout in the root cgroup changed much, just
> 0.31% slower on elapsed time for the compile, so no significant regressions
> there.  Now for sysbench again.
> 

Thanks a lot for testing report!
Alex
FROM centos:8
MAINTAINER Alexs 
#WORKDIR /vm-scalability 
#RUN yum update -y && yum groupinstall "Development Tools" -y && yum clean all && \
#examples https://www.linuxtechi.com/build-docker-container-images-with-dockerfile/
RUN yum install git xfsprogs patch make gcc -y && yum clean all && \
git clone  https://git.kernel.org/pub/scm/linux/kernel/git/wfg/vm-scalability.git/ && \
cd vm-scalability && make usemem

COPY readtwice.patch /vm-scalability/

RUN cd vm-scalability && patch -p1 < readtwice.patch
diff --git a/case-lru-file-readtwice b/case-lru-file-readtwice
index 85533b248634..57cb97d121ae 100755
--- a/case-lru-file-readtwice
+++ b/case-lru-file-readtwice
@@ -15,23 +15,30 @@
 
 . ./hw_vars
 
-for i in `seq 1 $nr_task`
-do
-	create_sparse_file $SPARSE_FILE-$i $((ROTATE_BYTES / nr_task))
-	timeout --foreground -s INT ${runtime:-600} dd bs=4k if=$SPARSE_FILE-$i of=/dev/null > $TMPFS_MNT/dd-output-1-$i 2>&1 &
-	timeout --foreground -s INT ${runtime:-600} dd bs=4k if=$SPARSE_FILE-$i of=/dev/null > $TMPFS_MNT/dd-output-2-$i 2>&1 &
-done
+OUT_DIR=$(hostname)-${nr_task}c-$(((mem + (1<<29))>>30))g
+TEST_CASES=${@:-$(echo case-*)}
+
+echo $((1<<30)) > /proc/sys/vm/max_map_count
+echo $((1<<20)) > /proc/sys/kernel/threads-max
+echo 1 > /proc/sys/vm/overcommit_memory
+#echo 3 > /proc/sys/vm/drop_caches
+
+
+i=1
+
+if [ "$1" == "m" ];then
+	mount_tmpfs
+	create_sparse_root
+	create_sparse_file $SPARSE_FILE-$i $((ROTATE_BYTES))
+	exit
+fi
+
+
+if [ "$1" == "r" ];then
+	(timeout --foreground -s INT ${runtime:-300} dd bs=4k if=$SPARSE_FILE-$i of=/dev/null > $TMPFS_MNT/dd-output-1-$i 2>&1)&
+	(timeout --foreground -s INT ${runtime:-300} dd bs=4k if=$SPARSE_FILE-$i of=/dev/null > $TMPFS_MNT/dd-output-2-$i 2>&1)&
+fi
 
 wait
 sleep 1
 
-for file in $TMPFS_MNT/dd-output-*
-do
-	[ -s "$file" ] || {
-		echo "dd output file empty: $file" >&2
-	}
-	cat $file
-	rm  $file
-done
-
-rm `seq -f $SPARSE_FILE-%g 1 $nr_task`
diff --git a/hw_vars b/hw_vars
index 8731cefb9f57..ceeaa9f17c0b 100755
--- a/hw_vars
+++ b/hw_vars
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/sh -ex
 
 if [ -n "$runtime" ]; then
 	USEMEM="$CMD ./usemem --runtime $runtime"
@@ -43,7 +43,7 @@ create_loop_devices()
 	modprobe loop 2>/dev/null
 	[ -e "/dev/loop0" ] || modprobe loop 2>/dev/null
 
-	for i in $(seq 0 8)
+	for i in $(seq 0 104)
 	do
 		[ -e "/dev/loop$i" ] && continue
 		mknod /dev/loop$i b 7 $i
@@ -101,11 +101,11 @@ remove_sparse_root () {
 create_sparse_file () {
 	name=$1
 	size=$2
-	# echo "$name is of size $size"
+	echo "$name is of size $size"
 	$CMD truncate $name -s $size
 	# dd if=/dev/zero of=$name bs=1k count=1 seek=$((size >> 10)) 2>/dev/null
-	# ls $SPARSE_ROOT
-	# ls /tmp/vm-scalability/*
+	ls $SPARSE_ROOT
+	ls /tmp/vm-scalability/*
 }