RE: [PoC] Non-volatile WAL buffer

Hi Gang,

Thanks. I have tried to reproduce performance degrade, using your configuration, query, and steps. And today, I got some results that Original (PMEM) achieved better performance than Non-volatile WAL buffer on my Ubuntu environment. Now I work for further investigation.

Best regards,
Takashi

--
Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp>
NTT Software Innovation Center

> -----Original Message-----
> From: Deng, Gang <gang(dot)deng(at)intel(dot)com>
> Sent: Friday, October 9, 2020 3:10 PM
> To: Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp>
> Cc: pgsql-hackers(at)postgresql(dot)org; 'Takashi Menjo' <takashi(dot)menjo(at)gmail(dot)com>
> Subject: RE: [PoC] Non-volatile WAL buffer
>
> Hi Takashi,
>
> There are some differences between our HW/SW configuration and test steps. I attached postgresql.conf I used
> for your reference. I would like to try postgresql.conf and steps you provided in the later days to see if I can find
> cause.
>
> I also ran pgbench and postgres server on the same server but on different NUMA node, and ensure server process
> and PMEM on the same NUMA node. I used similar steps are yours from step 1 to 9. But some difference in later
> steps, major of them are:
>
> In step 10), I created a database and table for test by:
> #create database:
> psql -c "create database insert_bench;"
> #create table:
> psql -d insert_bench -c "create table test(crt_time timestamp, info text default
> '75feba6d5ca9ff65d09af35a67fe962a4e3fa5ef279f94df6696bee65f4529a4bbb03ae56c3b5b86c22b447fc
> 48da894740ed1a9d518a9646b3a751a57acaca1142ccfc945b1082b40043e3f83f8b7605b5a55fcd7eb8fc1
> d0475c7fe465477da47d96957849327731ae76322f440d167725d2e2bbb60313150a4f69d9a8c9e86f9d7
> 9a742e7a35bf159f670e54413fb89ff81b8e5e8ab215c3ddfd00bb6aeb4');"
>
> in step 15), I did not use pg_prewarm, but just ran pg_bench for 180 seconds to warm up.
> In step 16), I ran pgbench using command: pgbench -M prepared -n -r -P 10 -f ./test.sql -T 600 -c _ -j _
> insert_bench. (test.sql can be found in attachment)
>
> For HW/SW conf, the major differences are:
> CPU: I used Xeon 8268 (24c(at)2(dot)9Ghz, HT enabled) OS Distro: CentOS 8.2.2004
> Kernel: 4.18.0-193.6.3.el8_2.x86_64
> GCC: 8.3.1
>
> Best regards
> Gang
>
> -----Original Message-----
> From: Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp>
> Sent: Tuesday, October 6, 2020 4:49 PM
> To: Deng, Gang <gang(dot)deng(at)intel(dot)com>
> Cc: pgsql-hackers(at)postgresql(dot)org; 'Takashi Menjo' <takashi(dot)menjo(at)gmail(dot)com>
> Subject: RE: [PoC] Non-volatile WAL buffer
>
> Hi Gang,
>
> I have tried to but yet cannot reproduce performance degrade you reported when inserting 328-byte records. So
> I think the condition of you and me would be different, such as steps to reproduce, postgresql.conf, installation
> setup, and so on.
>
> My results and condition are as follows. May I have your condition in more detail? Note that I refer to your "Storage
> over App Direct" as my "Original (PMEM)" and "NVWAL patch" to "Non-volatile WAL buffer."
>
> Best regards,
> Takashi
>
>
> # Results
> See the attached figure. In short, Non-volatile WAL buffer got better performance than Original (PMEM).
>
> # Steps
> Note that I ran postgres server and pgbench in a single-machine system but separated two NUMA nodes. PMEM
> and PCI SSD for the server process are on the server-side NUMA node.
>
> 01) Create a PMEM namespace (sudo ndctl create-namespace -f -t pmem -m fsdax -M dev -e namespace0.0)
> 02) Make an ext4 filesystem for PMEM then mount it with DAX option (sudo mkfs.ext4 -q -F /dev/pmem0 ; sudo
> mount -o dax /dev/pmem0 /mnt/pmem0)
> 03) Make another ext4 filesystem for PCIe SSD then mount it (sudo mkfs.ext4 -q -F /dev/nvme0n1 ; sudo mount
> /dev/nvme0n1 /mnt/nvme0n1)
> 04) Make /mnt/pmem0/pg_wal directory for WAL
> 05) Make /mnt/nvme0n1/pgdata directory for PGDATA
> 06) Run initdb (initdb --locale=C --encoding=UTF8 -X /mnt/pmem0/pg_wal ...)
> - Also give -P /mnt/pmem0/pg_wal/nvwal -Q 81920 in the case of Non-volatile WAL buffer
> 07) Edit postgresql.conf as the attached one
> - Please remove nvwal_* lines in the case of Original (PMEM)
> 08) Start postgres server process on NUMA node 0 (numactl -N 0 -m 0 -- pg_ctl -l pg.log start)
> 09) Create a database (createdb --locale=C --encoding=UTF8)
> 10) Initialize pgbench tables with s=50 (pgbench -i -s 50)
> 11) Change # characters of "filler" column of "pgbench_history" table to 300 (ALTER TABLE pgbench_history
> ALTER filler TYPE character(300);)
> - This would make the row size of the table 328 bytes
> 12) Stop the postgres server process (pg_ctl -l pg.log -m smart stop)
> 13) Remount the PMEM and the PCIe SSD
> 14) Start postgres server process on NUMA node 0 again (numactl -N 0 -m 0 -- pg_ctl -l pg.log start)
> 15) Run pg_prewarm for all the four pgbench_* tables
> 16) Run pgbench on NUMA node 1 for 30 minutes (numactl -N 1 -m 1 -- pgbench -r -M prepared -T 1800 -c __
> -j __)
> - It executes the default tpcb-like transactions
>
> I repeated all the steps three times for each (c,j) then got the median "tps = __ (including connections
> establishing)" of the three as throughput and the "latency average = __ ms " of that time as average latency.
>
> # Environment variables
> export PGHOST=/tmp
> export PGPORT=5432
> export PGDATABASE="$USER"
> export PGUSER="$USER"
> export PGDATA=/mnt/nvme0n1/pgdata
>
> # Setup
> - System: HPE ProLiant DL380 Gen10
> - CPU: Intel Xeon Gold 6240M x2 sockets (18 cores per socket; HT disabled by BIOS)
> - DRAM: DDR4 2933MHz 192GiB/socket x2 sockets (32 GiB per channel x 6 channels per socket)
> - Optane PMem: Apache Pass, AppDirect Mode, DDR4 2666MHz 1.5TiB/socket x2 sockets (256 GiB per channel
> x 6 channels per socket; interleaving enabled)
> - PCIe SSD: DC P4800X Series SSDPED1K750GA
> - Distro: Ubuntu 20.04.1
> - C compiler: gcc 9.3.0
> - libc: glibc 2.31
> - Linux kernel: 5.7 (vanilla)
> - Filesystem: ext4 (DAX enabled when using Optane PMem)
> - PMDK: 1.9
> - PostgreSQL (Original): 14devel (200f610: Jul 26, 2020)
> - PostgreSQL (Non-volatile WAL buffer): 14devel (200f610: Jul 26, 2020) + non-volatile WAL buffer patchset
> v4
>
> --
> Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp> NTT Software Innovation Center
>
> > -----Original Message-----
> > From: Takashi Menjo <takashi(dot)menjo(at)gmail(dot)com>
> > Sent: Thursday, September 24, 2020 2:38 AM
> > To: Deng, Gang <gang(dot)deng(at)intel(dot)com>
> > Cc: pgsql-hackers(at)postgresql(dot)org; Takashi Menjo
> > <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp>
> > Subject: Re: [PoC] Non-volatile WAL buffer
> >
> > Hello Gang,
> >
> > Thank you for your report. I have not taken care of record size deeply
> > yet, so your report is very interesting. I will also have a test like yours then post results here.
> >
> > Regards,
> > Takashi
> >
> >
> > 2020年9月21日(月) 14:14 Deng, Gang <gang(dot)deng(at)intel(dot)com <mailto:gang(dot)deng(at)intel(dot)com> >:
> >
> >
> > Hi Takashi,
> >
> >
> >
> > Thank you for the patch and work on accelerating PG performance with
> > NVM. I applied the patch and made some performance test based on the
> > patch v4. I stored database data files on NVMe SSD and stored WAL file on Intel PMem (NVM). I used two
> methods to store WAL file(s):
> >
> > 1. Leverage your patch to access PMem with libpmem (NVWAL patch).
> >
> > 2. Access PMem with legacy filesystem interface, that means use PMem as ordinary block device, no
> > PG patch is required to access PMem (Storage over App Direct).
> >
> >
> >
> > I tried two insert scenarios:
> >
> > A. Insert small record (length of record to be inserted is 24 bytes), I think it is similar as your test
> >
> > B. Insert large record (length of record to be inserted is 328 bytes)
> >
> >
> >
> > My original purpose is to see higher performance gain in scenario B as it is more write intensive on WAL.
> > But I observed that NVWAL patch method had ~5% performance improvement
> > compared with Storage over App Direct method in scenario A, while had ~20% performance degradation in
> scenario B.
> >
> >
> >
> > I made further investigation on the test. I found that NVWAL patch
> > can improve performance of XlogFlush function, but it may impact
> > performance of CopyXlogRecordToWAL function. It may be related to the higher latency of memcpy to Intel
> PMem comparing with DRAM. Here are key data in my test:
> >
> >
> >
> > Scenario A (length of record to be inserted: 24 bytes per record):
> >
> > ==============================
> >
> >
> > NVWAL SoAD
> >
> > ------------------------------------ ------- -------
> >
> > Througput (10^3 TPS) 310.5
> > 296.0
> >
> > CPU Time % of CopyXlogRecordToWAL 0.4 0.2
> >
> > CPU Time % of XLogInsertRecord 1.5 0.8
> >
> > CPU Time % of XLogFlush 2.1 9.6
> >
> >
> >
> > Scenario B (length of record to be inserted: 328 bytes per record):
> >
> > ==============================
> >
> >
> > NVWAL SoAD
> >
> > ------------------------------------ ------- -------
> >
> > Througput (10^3 TPS) 13.0
> > 16.9
> >
> > CPU Time % of CopyXlogRecordToWAL 3.0 1.6
> >
> > CPU Time % of XLogInsertRecord 23.0 16.4
> >
> > CPU Time % of XLogFlush 2.3 5.9
> >
> >
> >
> > Best Regards,
> >
> > Gang
> >
> >
> >
> > From: Takashi Menjo <takashi(dot)menjo(at)gmail(dot)com <mailto:takashi(dot)menjo(at)gmail(dot)com> >
> > Sent: Thursday, September 10, 2020 4:01 PM
> > To: Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp <mailto:takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp> >
> > Cc: pgsql-hackers(at)postgresql(dot)org <mailto:pgsql-hackers(at)postgresql(dot)org>
> > Subject: Re: [PoC] Non-volatile WAL buffer
> >
> >
> >
> > Rebased.
> >
> >
> >
> >
> >
> > 2020年6月24日(水) 16:44 Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp
> > <mailto:takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp> >:
> >
> > Dear hackers,
> >
> > I update my non-volatile WAL buffer's patchset to v3. Now we can
> > use it in streaming replication mode.
> >
> > Updates from v2:
> >
> > - walreceiver supports non-volatile WAL buffer
> > Now walreceiver stores received records directly to non-volatile WAL buffer if applicable.
> >
> > - pg_basebackup supports non-volatile WAL buffer
> > Now pg_basebackup copies received WAL segments onto non-volatile WAL
> > buffer if you run it with "nvwal" mode (-Fn).
> > You should specify a new NVWAL path with --nvwal-path option. The
> > path will be written to postgresql.auto.conf or recovery.conf. The size of the new NVWAL is same as the
> master's one.
> >
> >
> > Best regards,
> > Takashi
> >
> > --
> > Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp <mailto:takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp> >
> > NTT Software Innovation Center
> >
> > > -----Original Message-----
> > > From: Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp
> > <mailto:takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp> >
> > > Sent: Wednesday, March 18, 2020 5:59 PM
> > > To: 'PostgreSQL-development' <pgsql-hackers(at)postgresql(dot)org
> > <mailto:pgsql-hackers(at)postgresql(dot)org> >
> > > Cc: 'Robert Haas' <robertmhaas(at)gmail(dot)com
> > <mailto:robertmhaas(at)gmail(dot)com> >; 'Heikki Linnakangas' <hlinnaka(at)iki(dot)fi <mailto:hlinnaka(at)iki(dot)fi> >; 'Amit
> Langote'
> > > <amitlangote09(at)gmail(dot)com <mailto:amitlangote09(at)gmail(dot)com> >
> > > Subject: RE: [PoC] Non-volatile WAL buffer
> > >
> > > Dear hackers,
> > >
> > > I rebased my non-volatile WAL buffer's patchset onto master. A
> > new v2 patchset is attached to this mail.
> > >
> > > I also measured performance before and after patchset, varying
> > -c/--client and -j/--jobs options of pgbench, for
> > > each scaling factor s = 50 or 1000. The results are presented in
> > the following tables and the attached charts.
> > > Conditions, steps, and other details will be shown later.
> > >
> > >
> > > Results (s=50)
> > > ==============
> > > Throughput [10^3 TPS] Average latency [ms]
> > > ( c, j) before after before after
> > > ------- --------------------- ---------------------
> > > ( 8, 8) 35.7 37.1 (+3.9%) 0.224 0.216 (-3.6%)
> > > (18,18) 70.9 74.7 (+5.3%) 0.254 0.241 (-5.1%)
> > > (36,18) 76.0 80.8 (+6.3%) 0.473 0.446 (-5.7%)
> > > (54,18) 75.5 81.8 (+8.3%) 0.715 0.660 (-7.7%)
> > >
> > >
> > > Results (s=1000)
> > > ================
> > > Throughput [10^3 TPS] Average latency [ms]
> > > ( c, j) before after before after
> > > ------- --------------------- ---------------------
> > > ( 8, 8) 37.4 40.1 (+7.3%) 0.214 0.199 (-7.0%)
> > > (18,18) 79.3 86.7 (+9.3%) 0.227 0.208 (-8.4%)
> > > (36,18) 87.2 95.5 (+9.5%) 0.413 0.377 (-8.7%)
> > > (54,18) 86.8 94.8 (+9.3%) 0.622 0.569 (-8.5%)
> > >
> > >
> > > Both throughput and average latency are improved for each scaling
> > factor. Throughput seemed to almost reach
> > > the upper limit when (c,j)=(36,18).
> > >
> > > The percentage in s=1000 case looks larger than in s=50 case. I
> > think larger scaling factor leads to less
> > > contentions on the same tables and/or indexes, that is, less lock
> > and unlock operations. In such a situation,
> > > write-ahead logging appears to be more significant for performance.
> > >
> > >
> > > Conditions
> > > ==========
> > > - Use one physical server having 2 NUMA nodes (node 0 and 1)
> > > - Pin postgres (server processes) to node 0 and pgbench to node 1
> > > - 18 cores and 192GiB DRAM per node
> > > - Use an NVMe SSD for PGDATA and an interleaved 6-in-1 NVDIMM-N set for pg_wal
> > > - Both are installed on the server-side node, that is, node 0
> > > - Both are formatted with ext4
> > > - NVDIMM-N is mounted with "-o dax" option to enable Direct Access (DAX)
> > > - Use the attached postgresql.conf
> > > - Two new items nvwal_path and nvwal_size are used only after patch
> > >
> > >
> > > Steps
> > > =====
> > > For each (c,j) pair, I did the following steps three times then I
> > found the median of the three as a final result shown
> > > in the tables above.
> > >
> > > (1) Run initdb with proper -D and -X options; and also give
> > --nvwal-path and --nvwal-size options after patch
> > > (2) Start postgres and create a database for pgbench tables
> > > (3) Run "pgbench -i -s ___" to create tables (s = 50 or 1000)
> > > (4) Stop postgres, remount filesystems, and start postgres again
> > > (5) Execute pg_prewarm extension for all the four pgbench tables
> > > (6) Run pgbench during 30 minutes
> > >
> > >
> > > pgbench command line
> > > ====================
> > > $ pgbench -h /tmp -p 5432 -U username -r -M prepared -T 1800 -c ___ -j ___ dbname
> > >
> > > I gave no -b option to use the built-in "TPC-B (sort-of)" query.
> > >
> > >
> > > Software
> > > ========
> > > - Distro: Ubuntu 18.04
> > > - Kernel: Linux 5.4 (vanilla kernel)
> > > - C Compiler: gcc 7.4.0
> > > - PMDK: 1.7
> > > - PostgreSQL: d677550 (master on Mar 3, 2020)
> > >
> > >
> > > Hardware
> > > ========
> > > - System: HPE ProLiant DL380 Gen10
> > > - CPU: Intel Xeon Gold 6154 (Skylake) x 2sockets
> > > - DRAM: DDR4 2666MHz {32GiB/ch x 6ch}/socket x 2sockets
> > > - NVDIMM-N: DDR4 2666MHz {16GiB/ch x 6ch}/socket x 2sockets
> > > - NVMe SSD: Intel Optane DC P4800X Series SSDPED1K750GA
> > >
> > >
> > > Best regards,
> > > Takashi
> > >
> > > --
> > > Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp
> > <mailto:takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp> > NTT Software Innovation Center
> > >
> > > > -----Original Message-----
> > > > From: Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp
> > <mailto:takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp> >
> > > > Sent: Thursday, February 20, 2020 6:30 PM
> > > > To: 'Amit Langote' <amitlangote09(at)gmail(dot)com <mailto:amitlangote09(at)gmail(dot)com> >
> > > > Cc: 'Robert Haas' <robertmhaas(at)gmail(dot)com
> > <mailto:robertmhaas(at)gmail(dot)com> >; 'Heikki Linnakangas' <hlinnaka(at)iki(dot)fi <mailto:hlinnaka(at)iki(dot)fi> >;
> > > 'PostgreSQL-development'
> > > > <pgsql-hackers(at)postgresql(dot)org <mailto:pgsql-hackers(at)postgresql(dot)org> >
> > > > Subject: RE: [PoC] Non-volatile WAL buffer
> > > >
> > > > Dear Amit,
> > > >
> > > > Thank you for your advice. Exactly, it's so to speak "do as the hackers do when in pgsql"...
> > > >
> > > > I'm rebasing my branch onto master. I'll submit an updated
> > patchset and performance report later.
> > > >
> > > > Best regards,
> > > > Takashi
> > > >
> > > > --
> > > > Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp
> > <mailto:takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp>
> > > NTT Software
> > > > Innovation Center
> > > >
> > > > > -----Original Message-----
> > > > > From: Amit Langote <amitlangote09(at)gmail(dot)com <mailto:amitlangote09(at)gmail(dot)com> >
> > > > > Sent: Monday, February 17, 2020 5:21 PM
> > > > > To: Takashi Menjo <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp
> > <mailto:takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp> >
> > > > > Cc: Robert Haas <robertmhaas(at)gmail(dot)com
> > <mailto:robertmhaas(at)gmail(dot)com> >; Heikki Linnakangas
> > > > > <hlinnaka(at)iki(dot)fi <mailto:hlinnaka(at)iki(dot)fi> >; PostgreSQL-development
> > > > > <pgsql-hackers(at)postgresql(dot)org <mailto:pgsql-hackers(at)postgresql(dot)org> >
> > > > > Subject: Re: [PoC] Non-volatile WAL buffer
> > > > >
> > > > > Hello,
> > > > >
> > > > > On Mon, Feb 17, 2020 at 4:16 PM Takashi Menjo
> > <takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp <mailto:takashi(dot)menjou(dot)vg(at)hco(dot)ntt(dot)co(dot)jp> > wrote:
> > > > > > Hello Amit,
> > > > > >
> > > > > > > I apologize for not having any opinion on the patches
> > > > > > > themselves, but let me point out that it's better to base these
> > > > > > > patches on HEAD (master branch) than REL_12_0, because all new
> > > > > > > code is committed to the master branch, whereas stable branches
> > > > > > > such as
> > > > > > > REL_12_0 only receive bug fixes. Do you have any
> > > > > specific reason to be working on REL_12_0?
> > > > > >
> > > > > > Yes, because I think it's human-friendly to reproduce and discuss
> > > > > > performance measurement. Of course I know
> > > > > all new accepted patches are merged into master's HEAD, not stable
> > > > > branches and not even release tags, so I'm aware of rebasing my
> > > > > patchset onto master sooner or later. However, if someone,
> > > > > including me, says that s/he applies my patchset to "master" and
> > > > > measures its performance, we have to pay attention to which commit the "master"
> > > > > really points to. Although we have sha1 hashes to specify which
> > > > > commit, we should check whether the specific commit on master has
> > > > > patches affecting performance or not
> > > > because master's HEAD gets new patches day by day. On the other hand,
> > > > a release tag clearly points the commit all we probably know. Also we
> > > > can check more easily the features and improvements by using
> > release notes and user manuals.
> > > > >
> > > > > Thanks for clarifying. I see where you're coming from.
> > > > >
> > > > > While I do sometimes see people reporting numbers with the latest
> > > > > stable release' branch, that's normally just one of the baselines.
> > > > > The more important baseline for ongoing development is the master
> > > > > branch's HEAD, which is also what people volunteering to test your
> > > > > patches would use. Anyone who reports would have to give at least
> > > > > two numbers -- performance with a branch's HEAD without patch
> > > > > applied and that with patch applied -- which can be enough in most
> > > > > cases to see the difference the patch makes. Sure, the numbers
> > > > > might change on each report, but that's fine I'd think. If you
> > > > > continue to develop against the stable branch, you might miss to
> > > > notice impact from any relevant developments in the master branch,
> > > > even developments which possibly require rethinking the
> > architecture of your own changes, although maybe that
> > > rarely occurs.
> > > > >
> > > > > Thanks,
> > > > > Amit
> >
> >
> >
> >
> >
> >
> > --
> >
> > Takashi Menjo <takashi(dot)menjo(at)gmail(dot)com
> > <mailto:takashi(dot)menjo(at)gmail(dot)com> >
> >
> >
> >
> > --
> >
> > Takashi Menjo <takashi(dot)menjo(at)gmail(dot)com
> > <mailto:takashi(dot)menjo(at)gmail(dot)com> >