一个编译参数引起的ceph性能大幅下降

背景

最近翻ceph的官方的博客，发现了一篇博客提到了一个ubuntu下面的编译参数引起的rocksdb的性能下降，这个地方应该是ceph官方代码的参数没生效

受影响的系统

• P版本之前的ceph版本
• 操作系统是ubuntu的
• 某些ceph版本

这个要素比较多，所以运行的环境并不一定受到影响，那么我们看下，收到影响的版本是哪些,非ubuntu的系统可以忽略这个问题

我对15的版本比较熟，就以这个版本举例子

受到影响的版本

这个版本是从ceph官方同步过来的版本

https://mirrors.tuna.tsinghua.edu.cn/ceph/debian-15.2.17/pool/main/c/ceph/

不受影响的版本

https://launchpad.net/ubuntu/focal/+source/ceph

这个是ubuntu官方打包的版本

下载不同的版本

源文件

root@lab103:~# cat /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu/ focal main restricted
deb http://archive.ubuntu.com/ubuntu/ focal-updates main restricted
deb http://archive.ubuntu.com/ubuntu/ focal universe
deb http://archive.ubuntu.com/ubuntu/ focal-updates universe
deb http://archive.ubuntu.com/ubuntu/ focal multiverse
deb http://archive.ubuntu.com/ubuntu/ focal-updates multiverse
deb http://archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu/ focal-security main restricted
deb http://security.ubuntu.com/ubuntu/ focal-security universe
deb http://security.ubuntu.com/ubuntu/ focal-security multiverse
deb [trusted=yes]  https://mirrors.tuna.tsinghua.edu.cn/ceph/debian-15.2.17 focal  main

上面的源是安装ceph的软件包的，如果屏蔽掉最后一行，安装的就是ubuntu官方的版本，如果留着最后一行，安装的就是ceph官方的版本，包的名称不一样，这个很好区分

两个版本的区别

我们下载ubuntu官方的debian的打包文件

wget https://launchpad.net/ubuntu/+archive/primary/+sourcefiles/ceph/15.2.17-0ubuntu0.20.04.6/ceph_15.2.17-0ubuntu0.20.04.6.debian.tar.xz

ubuntu的官方的包是把debian的目录剥离出来的

我们再下载ceph官方的源码包，这个跟git里面是同步的我们看下内容

wget https://mirrors.tuna.tsinghua.edu.cn/ceph/debian-15.2.17/pool/main/c/ceph/ceph_15.2.17.orig.tar.gz

ceph的官方包里面是有debian目录的，我们直接查看内容

我们需要比对的是debian/rules里面的内容

ubuntu官方的

## Set JAVAC to prevent FTBFS due to incorrect use of 'gcj' if found (see "m4/ac_prog_javac.m4").
export JAVAC=javac

extraopts += -DWITH_OCF=ON -DWITH_NSS=ON -DWITH_PYTHON3=ON -DWITH_DEBUG=ON
extraopts += -DWITH_PYTHON2=OFF -DMGR_PYTHON_VERSION=3
extraopts += -DWITH_CEPHFS_JAVA=ON
extraopts += -DWITH_CEPHFS_SHELL=ON
extraopts += -DWITH_TESTS=OFF
extraopts += -DWITH_SYSTEM_BOOST=ON
extraopts += -DWITH_LTTNG=OFF -DWITH_EMBEDDED=OFF
extraopts += -DCMAKE_INSTALL_LIBEXECDIR=/usr/lib
extraopts += -DWITH_MGR_DASHBOARD_FRONTEND=OFF
extraopts += -DWITH_SYSTEMD=ON -DCEPH_SYSTEMD_ENV_DIR=/etc/default
extraopts += -DCMAKE_INSTALL_SYSCONFDIR=/etc
extraopts += -DCMAKE_INSTALL_SYSTEMD_SERVICEDIR=/lib/systemd/system
extraopts += -DWITH_RADOSGW_KAFKA_ENDPOINT=OFF
extraopts += -DCMAKE_BUILD_TYPE=RelWithDebInfo

ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
  NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
  extraopts += -DBOOST_J=$(NUMJOBS)
endif

ceph官方的

extraopts += -DWITH_OCF=ON -DWITH_LTTNG=ON
extraopts += -DWITH_MGR_DASHBOARD_FRONTEND=OFF
extraopts += -DWITH_PYTHON3=3
extraopts += -DWITH_CEPHFS_JAVA=ON
extraopts += -DWITH_CEPHFS_SHELL=ON
extraopts += -DWITH_SYSTEMD=ON -DCEPH_SYSTEMD_ENV_DIR=/etc/default
extraopts += -DWITH_GRAFANA=ON
# assumes that ceph is exmpt from multiarch support, so we override the libdir.
extraopts += -DCMAKE_INSTALL_LIBDIR=/usr/lib
extraopts += -DCMAKE_INSTALL_LIBEXECDIR=/usr/lib
extraopts += -DCMAKE_INSTALL_SYSCONFDIR=/etc
extraopts += -DCMAKE_INSTALL_SYSTEMD_SERVICEDIR=/lib/systemd/system
ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
  NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
  extraopts += -DBOOST_J=$(NUMJOBS)
endif

区别就是这个

extraopts += -DCMAKE_BUILD_TYPE=RelWithDebInfo

RelWithDebInfo: 既优化又能调试的版本

这个参数带来的效果是

-DCMAKE_CXX_FLAGS='-Wno-deprecated-copy -Wno-pessimizing-move'"

会带来这两个参数，以及一些其它的关闭，属于生产包需要加这个参数好一点

ceph官方是放在自己的cmake里面控制，但是deb打包的时候，有自己的这个参数，变量就被冲掉了，也就是没生效

https://github.com/ceph/ceph/pull/55500

官方现在改了，应该是解决了，但是ubuntu官方里面是直接在最上层就用参数去控制了，也就没有这个问题
修改cmake/modules/BuildRocksDB.cmake

endif()
  include(CheckCXXCompilerFlag)
  check_cxx_compiler_flag("-Wno-deprecated-copy" HAS_WARNING_DEPRECATED_COPY)
  set(rocksdb_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
  if(HAS_WARNING_DEPRECATED_COPY)
-    set(rocksdb_CXX_FLAGS -Wno-deprecated-copy)
+    string(APPEND rocksdb_CXX_FLAGS " -Wno-deprecated-copy")
  endif()
  check_cxx_compiler_flag("-Wno-pessimizing-move" HAS_WARNING_PESSIMIZING_MOVE)
  if(HAS_WARNING_PESSIMIZING_MOVE)
-    set(rocksdb_CXX_FLAGS "${rocksdb_CXX_FLAGS} -Wno-pessimizing-move")
+    string(APPEND rocksdb_CXX_FLAGS " -Wno-pessimizing-move")
  endif()
  if(rocksdb_CXX_FLAGS)
    list(APPEND rocksdb_CMAKE_ARGS -DCMAKE_CXX_FLAGS='${rocksdb_CXX_FLAGS}')

打包过程可以看到这两个参数加进去了没

[  8%] Performing configure step for 'rocksdb_ext'
cd /ceph/ceph-15.2.17/obj-x86_64-linux-gnu/src/rocksdb && /usr/bin/cmake -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DWITH_GFLAGS=OFF -DCMAKE_PREFIX_PATH= -DCMAKE_CXX_COMPILER=/usr/bin/c++ -DWITH_SNAPPY=TRUE -DWITH_LZ4=TRUE -DLZ4_INCLUDE_DIR=/usr/include -DLZ4_LIBRARIES=/usr/lib/x86_64-linux-gnu/liblz4.so -DWITH_ZLIB=TRUE -DPORTABLE=ON -DCMAKE_AR=/usr/bin/ar -DCMAKE_BUILD_TYPE=RelWithDebInfo -DFAIL_ON_WARNINGS=OFF -DUSE_RTTI=1 "-GUnix Makefiles" -DCMAKE_C_FLAGS=-Wno-stringop-truncation "-DCMAKE_CXX_FLAGS=' -Wno-deprecated-copy -Wno-pessimizing-move'" "-GUnix Makefiles" /ceph/ceph-15.2.17/src/rocksdb
-- Build files have been written to: /ceph/ceph-15.2.17/obj-x86_64-linux-gnu/src/rocksdb

那么我们整体捋一捋

- ceph在代码里面加了参数，参数被打包过程冲掉了，引起了性能下降
- ubuntu在打包ceph里面加另外一个参数，让这两个参数生效了，所以打出来的包没有问题

大概就是这么回事，差不多就是发行版本出的包，没有按优化的版本打包，问题很小，影响还比较大，如果正好使用的就是这个ubuntu的官方包的话

性能测试

上面是说了这个问题的来源，我们来体验一下这个性能的区别

为了测试的准确性，构建了一个单机，单副本的环境，单个nvme的osd，在宿主机创建好osd之后，停止osd，然后把osd映射到docker里面进行手动启动

这样做的目的是，osd不变，减少变量，容器系统一致，只替换了ceph的包

容器启动方式

docker run -it --privileged=true -v /dev/:/dev/ -v /var/lib/ceph/:/var/lib/ceph -v /etc/ceph:/etc/ceph --network host ubuntu:focal /bin/bash --name ceph_deb

ceph官方包

root@lab103:/# dpkg --list|grep ceph
ii  ceph                                 15.2.17-1focal                    amd64        distributed storage and file system

手动启动osd

/usr/bin/ceph-osd -f --cluster ceph --id 0 --setuser ceph --setgroup ceph

测试

rados -p data bench 30 write -b 4096

也可以用其它命令，小io4k的比较明显,时间不久，就都贴上来

[root@lab103 zp]# rados -p data bench 30 write -b 4096
hints = 1
Maintaining 16 concurrent writes of 4096 bytes to objects of size 4096 for up to 30 seconds or 0 objects
Object prefix: benchmark_data_lab103_235759
  sec Cur ops   started  finished  avg MB/s  cur MB/s last lat(s)  avg lat(s)
    0       0         0         0         0         0           -           0
    1      16      6811      6795   26.5416    26.543  0.00314961  0.00234824
    2      15     13061     13046   25.4781    24.418  0.00280007  0.00244734
    3      16     18804     18788   24.4609   22.4297  0.00179994  0.00255073
    4      16     24430     24414    23.839   21.9766   0.0027436  0.00261775
    5      16     29900     29884   23.3441   21.3672  0.00184661  0.00267347
    6      16     35338     35322   22.9932   21.2422  0.00376749  0.00271445
    7      16     40864     40848   22.7917   21.5859   0.0023982  0.00273855
    8      16     46654     46638   22.7695   22.6172  0.00265023   0.0027412
    9      15     52491     52476   22.7731   22.8047  0.00237885  0.00274086
   10      16     58334     58318   22.7775   22.8203   0.0032622  0.00274042
   11      16     64011     63995   22.7224   22.1758  0.00224359  0.00274685
   12      16     69693     69677   22.6782   22.1953  0.00282742  0.00275244
   13      16     75483     75467   22.6733   22.6172   0.0024294  0.00275293
   14      16     81331     81315   22.6852   22.8438  0.00243682  0.00275157
   15      16     87110     87094   22.6776   22.5742  0.00249853  0.00275236
   16      16     92892     92876   22.6717   22.5859  0.00234551  0.00275325
   17      16     98682     98666   22.6683   22.6172  0.00279748  0.00275354
   18      16    104350    104334   22.6388   22.1406  0.00247821  0.00275716
   19      16    110108    110092   22.6309   22.4922  0.00265833  0.00275813
2024-03-21T18:09:10.318468+0800 min lat: 0.000901059 max lat: 0.0108369 avg lat: 0.00275815
  sec Cur ops   started  finished  avg MB/s  cur MB/s last lat(s)  avg lat(s)
   20      16    115907    115891   22.6318   22.6523  0.00308136  0.00275815
   21      16    121632    121616   22.6188   22.3633  0.00107606  0.00275984
   22      16    127334    127318   22.6029   22.2734  0.00307552  0.00276152
   23      16    133012    132996   22.5844   22.1797  0.00268477  0.00276388
   24      16    138652    138636   22.5612   22.0312  0.00284827  0.00276685
   25      16    144273    144257   22.5369    21.957   0.0022021  0.00276986
   26      16    149771    149755    22.496   21.4766  0.00333811  0.00277466
   27      16    155250    155234   22.4553   21.4023  0.00249963  0.00277992
   28      16    160745    160729   22.4199   21.4648  0.00245874  0.00278427
   29      16    166247    166231   22.3878   21.4922  0.00295188  0.00278836
Total time run:         30.0023
Total writes made:      171762
Write size:             4096
Object size:            4096
Bandwidth (MB/sec):     22.3631
Stddev Bandwidth:       1.02477
Max bandwidth (MB/sec): 26.543
Min bandwidth (MB/sec): 21.2422
Average IOPS:           5724
Stddev IOPS:            262.341
Max IOPS:               6795
Min IOPS:               5438
Average Latency(s):     0.00279145
Stddev Latency(s):      0.000623496
Max latency(s):         0.0108369
Min latency(s):         0.000901059
Cleaning up (deleting benchmark objects)
Removed 171762 objects
Clean up completed and total clean up time :30.6685

ubuntu官方包

root@lab103:/# dpkg --list|grep ceph
root@lab103:/# dpkg --list|grep ceph
ii  ceph                                 15.2.17-0ubuntu0.20.04.6          amd64        distributed storage and file system
ii  ceph-base                            15.2.17-0ubuntu0.20.04.6          amd64        common ceph daemon libraries and management tools

手动启动osd

/usr/bin/ceph-osd -f --cluster ceph --id 0 --setuser ceph --setgroup ceph

测试

rados -p data bench 30 write -b 4096

[root@lab103 zp]# rados -p data bench 30 write -b 4096
hints = 1
Maintaining 16 concurrent writes of 4096 bytes to objects of size 4096 for up to 30 seconds or 0 objects
Object prefix: benchmark_data_lab103_236362
  sec Cur ops   started  finished  avg MB/s  cur MB/s last lat(s)  avg lat(s)
    0       0         0         0         0         0           -           0
    1      16     15303     15287   59.7107   59.7148  0.00106137  0.00104294
    2      16     30338     30322   59.2169   58.7305 0.000799582  0.00105216
    3      16     46691     46675   60.7683   63.8789  0.00116935  0.00102532
    4      16     62548     62532   61.0597   61.9414 0.000970205  0.00102051
    5      16     78056     78040   60.9618   60.5781 0.000754982  0.00102213
    6      16     93210     93194   60.6659   59.1953 0.000796767  0.00102717
    7      16    108491    108475   60.5256   59.6914 0.000820318   0.0010296
    8      15    123545    123530     60.31   58.8086  0.00117671  0.00103331
    9      15    139028    139013   60.3281   60.4805   0.0010041  0.00103303
   10      16    154628    154612   60.3878   60.9336  0.00106916  0.00103203
   11      16    169869    169853   60.3095   59.5352  0.00100121  0.00103337
   12      16    185143    185127    60.255   59.6641 0.000874392  0.00103434
   13      16    200261    200245    60.162   59.0547 0.000937596  0.00103596
   14      16    212138    212122   59.1782   46.3945 0.000740705  0.00105322
   15      16    227092    227076   59.1267   58.4141 0.000774189  0.00105417
   16      16    241651    241635   58.9853   56.8711  0.00140325  0.00105664
   17      16    257762    257746    59.217   62.9336 0.000777715  0.00105251
   18      15    273338    273323   59.3072   60.8477 0.000842773  0.00105092
   19      16    288882    288866   59.3808   60.7148 0.000944547  0.00104963
2024-03-21T18:13:37.381819+0800 min lat: 0.000545632 max lat: 0.037882 avg lat: 0.00104838
  sec Cur ops   started  finished  avg MB/s  cur MB/s last lat(s)  avg lat(s)
   20      16    304446    304430   59.4512   60.7969 0.000774379  0.00104838
   21      16    320053    320037   59.5228   60.9648 0.000891544  0.00104713
   22      16    335395    335379   59.5409   59.9297  0.00105081  0.00104681
   23      16    351159    351143   59.6291   61.5781 0.000691308  0.00104527
   24      15    365701    365686   59.5112   56.8086 0.000910524  0.00104736
   25      16    381282    381266   59.5649   60.8594 0.000934152  0.00104642
   26      16    396656    396640   59.5834   60.0547 0.000904033  0.00104609
   27      15    411989    411974   59.5947   59.8984  0.00273626  0.00104583
   28      16    424394    424378   59.1965   48.4531 0.000757671  0.00105296
   29      15    435855    435840   58.6989   44.7734  0.00237303  0.00106191
Total time run:         30.0008
Total writes made:      449321
Write size:             4096
Object size:            4096
Bandwidth (MB/sec):     58.5038
Stddev Bandwidth:       4.48913
Max bandwidth (MB/sec): 63.8789
Min bandwidth (MB/sec): 44.7734
Average IOPS:           14976
Stddev IOPS:            1149.22
Max IOPS:               16353
Min IOPS:               11462
Average Latency(s):     0.00106545
Stddev Latency(s):      0.000482816
Max latency(s):         0.0431733
Min latency(s):         0.00047586
Cleaning up (deleting benchmark objects)
Removed 449321 objects
Clean up completed and total clean up time :22.541

一个iops 14976(58MB/s) - ubuntu的包
一个iops是5724(22MB/s) - ceph的包

可以看到差距还是很明显的

这个如果正好碰到了，可以按ubuntu这个方式改下debian的rule，或者把ceph的pr弄进去重新打包即可，具体验证有没有问题，可以通过检查下打包的参数或者直接单机验证下性能也可以