11:20 a.m.
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Oh wow, this is just a matter of me using the wrong LMDB version? I had no =
idea I wasn=E2=80=99t using the release version. I=E2=80=99ve been using ht=
tps://github.com/Venemo/node-lmdb, which includes LMDB directly in it, and =
had assumed that the version number in the code implied a release. I can pu=
t together a PR for that project to get it on the right version.
Thank you so much the pointer, I appreciate! And thank you so much for the =
great software, its a fantastic package!
Thanks,
Kris
From: Howard Chu
Sent: February 5, 2019 12:03 PM
To: kriszyp(a)gmail.com; openldap-its(a)OpenLDAP.org
Subject: Re: (ITS#8972) Performance/freezing issues using NTDLL on WindowsS=
erver on Azure
kriszyp(a)gmail.com wrote:
Full_Name: Kristopher William Zyp
Version: LMDB 0.9.70
OS: Windows Server 2012 R2
URL:=20
Submission from: (NULL) (71.199.6.148)
I guess Windows users are never happy.
Note that you're using the LMDB work-in-progress code. You ought to be usin=
g the
LMDB 0.9 release branch, which just uses Win32.
The fact is that you get optimal performance by using LMDB as originally de=
signed
and documented - choose as large a mapsize as possible and then forget abou=
t it.
Preallocation is always more efficient than incremental growth.
Clearly Windows will struggle to allocate disk space to grow files and addr=
ess
space to grow maps while there's competing system activity occurring, and t=
his
problem is worse when running under a hypervisor. This is the reason we nev=
er
merged the NTDLL code into the release branch; we knew from the outset that=
it
would destroy performance.
https://openldap.org/lists/openldap-technical/201511/msg00107.html
As a general rule, we're opposed to adding platform-specific API options to=
LMDB.
The API is supposed to be uniform across all supported platforms. If you wa=
nt to
submit a patch for compile-time selection of this feature, I guess that cou=
ld
work. As it is, LMDB is clearly not going to be a preinstalled Windows DLL =
so
it should be being built privately for every app that uses it anyway, so th=
is
shouldn't cause compatibility issues.
We have experienced significant performance issues in the form of
strange=
pauses
or freezing of any processes that are using our LMDB databases. These
pau=
ses are
periodic, often every few minutes, and typically completely freeze a
proc=
ess for
about 5 seconds, sometimes less, sometimes as much as a minute. They
ofte=
n occur
when the process is completely idle (we have a sleep timer to monitor
for=
them),
but we also see a lot of unusually large pauses on commits too. We
have n=
ever
been able to reproduce any of these issues with our local machines
runnin=
g
Windows 10, only on the virtual Azure Windows servers.
=20
After weeks of investigation, we finally realized that all of these stran=
ge
performance issues seemed to be due to the use of NTDLL for memory
mappin=
g. I
swapped out the NtCreateSection/NtMapViewOfSection calls for standard
Win=
32
CreateFileMapping/MapViewOfFile calls to create the memory map, and
sudde=
nly
these issues went away, and performance dramatically improved. Making
thi=
s
switch does mean you lose the progressive file allocation
functionality o=
f
NtCreateSection, but this is a small price to pay for the vast
performanc=
e
benefit of using standard file mapping.
=20
Anyway, my request is to simply to provide an option to use CreateFileMap=
ping
API instead of NtCreateSection. I recognize that the NTDLL based APIs
may=
be
more convenient for many users, but an option to use the standard
APIs, e=
ven if
it means the entire map is pre-allocated in the file size, is well
worth =
it for
the gains. I also recognize that Windows isn't the first choice
of LMDB, =
but
performance with these standard APIs is very good.
=20
I'd be happy to work on putting together a branch/pull request to address=
this.
However, your repository is a little different than typical github
reposi=
tories,
so I wanted to know if that was doable, and if there was a proper way
to =
submit
a PR, or if it needs to be submitted through this ticket system as a
patc=
h.
http://www.openldap.org/devel/contributing.html
--=20
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/
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--></style></head><body lang=3DEN-CA link=3Dblue
vlink=3D"#954F72"><div cla=
ss=3DWordSection1><p class=3DMsoNormal>Oh wow, this is just a matter of me =
using the wrong LMDB version? I had no idea I wasn=E2=80=99t using the rele=
ase version. I=E2=80=99ve been using <a href=3D"https://github.com/Venemo/n=
ode-lmdb">https://github.com/Venemo/node-lmdb</a>;, which includes LMDB
dire=
ctly in it, and had assumed that the version number in the code implied a r=
elease. I can put together a PR for that project to get it on the right ver=
sion.</p><p class=3DMsoNormal>Thank you so much the pointer, I appreciate! =
And thank you so much for the great software, its a fantastic package!</p><=
p class=3DMsoNormal><o:p> </o:p></p><p
class=3DMsoNormal>Thanks,<br>Kr=
is</p><p class=3DMsoNormal><o:p> </o:p></p><div
style=3D'mso-element:p=
ara-border-div;border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm=
0cm 0cm'><p class=3DMsoNormal
style=3D'border:none;padding:0cm'><b>From: <=
/b><a href=3D"mailto:hyc@symas.com">Howard
Chu</a><br><b>Sent: </b>February=
5, 2019 12:03 PM<br><b>To: </b><a
href=3D"mailto:kriszyp@gmail.com">kriszy=
p(a)gmail.com</a>; <a
href=3D"mailto:openldap-its@OpenLDAP.org">openldap-its@=
OpenLDAP.org</a><br><b>Subject: </b>Re: (ITS#8972)
Performance/freezing iss=
ues using NTDLL on WindowsServer on Azure</p></div><p
class=3DMsoNormal><o:=
p> </o:p></p><p class=3DMsoNormal>kriszyp(a)gmail.com
wrote:</p><p class=
=3DMsoNormal>> Full_Name: Kristopher William Zyp</p><p
class=3DMsoNormal=
> Version: LMDB 0.9.70</p><p
class=3DMsoNormal>> OS: Windows Server =
2012 R2</p><p
class=3DMsoNormal>> URL: </p><p class=3DMsoNormal>> Sub=
mission from: (NULL) (71.199.6.148)</p><p
class=3DMsoNormal><o:p> </o:=
p></p><p class=3DMsoNormal>I guess Windows users are never
happy.</p><p cla=
ss=3DMsoNormal><o:p> </o:p></p><p
class=3DMsoNormal>Note that you're u=
sing the LMDB work-in-progress code. You ought to be using the</p><p class=
=3DMsoNormal>LMDB 0.9 release branch, which just uses Win32.</p><p class=3D=
MsoNormal><o:p> </o:p></p><p class=3DMsoNormal>The
fact is that you ge=
t optimal performance by using LMDB as originally designed</p><p class=3DMs=
oNormal>and documented - choose as large a mapsize as possible and then for=
get about it.</p><p class=3DMsoNormal>Preallocation is always more efficien=
t than incremental growth.</p><p
class=3DMsoNormal><o:p> </o:p></p><p =
class=3DMsoNormal>Clearly Windows will struggle to allocate disk space to g=
row files and address</p><p class=3DMsoNormal>space to grow maps while ther=
e's competing system activity occurring, and this</p><p
class=3DMsoNormal>p=
roblem is worse when running under a hypervisor. This is the reason we neve=
r</p><p class=3DMsoNormal>merged the NTDLL code into the release branch; we=
knew from the outset that it</p><p class=3DMsoNormal>would destroy perform=
ance.</p><p class=3DMsoNormal><o:p> </o:p></p><p
class=3DMsoNormal>htt=
ps://openldap.org/lists/openldap-technical/201511/msg00107.html</p>... class=
=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNormal>As a
general rule, w=
e're opposed to adding platform-specific API options to LMDB.</p><p class=
=3DMsoNormal>The API is supposed to be uniform across all supported platfor=
ms. If you want to</p><p class=3DMsoNormal>submit a patch for compile-time =
selection of this feature, I guess that could</p><p class=3DMsoNormal>work.=
As it is, LMDB is clearly not going to be a preinstalled Windows DLL so</p=
<p class=3DMsoNormal>it should be being built privately for
every app that=
uses it anyway, so this</p><p
class=3DMsoNormal>shouldn't cause compatibil=
ity issues.</p><p
class=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNorm=
al>> We have experienced significant performance issues in the form of s=
trange pauses</p><p class=3DMsoNormal>> or freezing of any processes
tha=
t are using our LMDB databases. These pauses are</p><p
class=3DMsoNormal>&g=
t; periodic, often every few minutes, and typically completely freeze a pro=
cess for</p><p class=3DMsoNormal>> about 5 seconds, sometimes less,
some=
times as much as a minute. They often occur</p><p class=3DMsoNormal>>
wh=
en the process is completely idle (we have a sleep timer to monitor for the=
m),</p><p class=3DMsoNormal>> but we also see a lot of unusually large
p=
auses on commits too. We have never</p><p class=3DMsoNormal>> been able
=
to reproduce any of these issues with our local machines running</p><p clas=
s=3DMsoNormal>> Windows 10, only on the virtual Azure Windows servers.</=
p><p class=3DMsoNormal>> </p><p class=3DMsoNormal>>
After weeks of in=
vestigation, we finally realized that all of these strange</p><p class=3DMs=
oNormal>> performance issues seemed to be due to the use of NTDLL for me=
mory mapping. I</p><p class=3DMsoNormal>> swapped out the
NtCreateSectio=
n/NtMapViewOfSection calls for standard Win32</p><p class=3DMsoNormal>>
=
CreateFileMapping/MapViewOfFile calls to create the memory map, and suddenl=
y</p><p class=3DMsoNormal>> these issues went away, and performance
dram=
atically improved. Making this</p><p class=3DMsoNormal>> switch does
mea=
n you lose the progressive file allocation functionality of</p><p class=3DM=
soNormal>> NtCreateSection, but this is a small price to pay for the vas=
t performance</p><p class=3DMsoNormal>> benefit of using standard file
m=
apping.</p><p class=3DMsoNormal>> </p><p
class=3DMsoNormal>> Anyway, =
my request is to simply to provide an option to use CreateFileMapping</p><p=
class=3DMsoNormal>> API instead of NtCreateSection. I recognize that th=
e NTDLL based APIs may be</p><p class=3DMsoNormal>> more convenient for
=
many users, but an option to use the standard APIs, even if</p><p class=3DM=
soNormal>> it means the entire map is pre-allocated in the file size, is=
well worth it for</p><p class=3DMsoNormal>> the gains. I also
recognize=
that Windows isn't the first choice of LMDB, but</p><p
class=3DMsoNormal>&=
gt; performance with these standard APIs is very good.</p><p class=3DMsoNor=
mal>> </p><p class=3DMsoNormal>> I'd be happy to work on
putting toge=
ther a branch/pull request to address this.</p><p class=3DMsoNormal>>
Ho=
wever, your repository is a little different than typical github repositori=
es,</p><p class=3DMsoNormal>> so I wanted to know if that was doable,
an=
d if there was a proper way to submit</p><p class=3DMsoNormal>> a PR,
or=
if it needs to be submitted through this ticket system as a patch.</p><p c=
lass=3DMsoNormal><o:p> </o:p></p><p
class=3DMsoNormal>http://www.openl=
dap.org/devel/contributing.html</p><p
class=3DMsoNormal><o:p> </o:p></=
p><p class=3DMsoNormal>-- </p><p class=3DMsoNormal>=C2=A0=C2=A0--
Howard Ch=
u</p><p class=3DMsoNormal>=C2=A0 CTO, Symas Corp.=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 http://www.symas.com</p><p class=3DMso=
Normal>=C2=A0 Director, Highland Sun=C2=A0=C2=A0=C2=A0=C2=A0 http://highlan=
dsun.com/hyc/</p><p class=3DMsoNormal> =C2=A0Chief Architect, OpenLDAP=C2=
=A0 http://www.openldap.org/project/</p><p
class=3DMsoNormal><o:p> </o=
:p></p></div></body></html>=
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