[gdal-dev] GDAL Overestimating Physical Memory
Angus Dickey
angus at myheat.ca
Thu Jan 26 15:13:07 PST 2023
Even,
I pulled the updated PR and it is working well in a Linux container:
$ ./get_gdal_memory
GDAL version is 3.7.0dev
GDAL thinks it has 2097152000 bytes of physical memory
GDAL thinks it has 2097152000 bytes of usable physical memory
sysinfo() thinks it has 811526475776 bytes of physical memory
Thank you for this change, it should make GDAL in LXCs much more stable.
Maybe someday sysinfo()
<https://man7.org/linux/man-pages/man2/sysinfo.2.html> will be updated
to understand cgroup v2 or a new library function will be created to make
this easier for you.
Angus
On Thu, Jan 26, 2023 at 7:52 AM Even Rouault <even.rouault at spatialys.com>
wrote:
> Angus,
>
> I've just edited the pull request to take into account MemTotal of
> /proc/meminfo. Only tested on my host Linux, but hopefully that should work
> also for your setup given the elements you've mentionned.
>
> Laurențiu,
>
> are you 100% positive you've tested the updated version of the pull
> request? I've just given a try to running gdallimits under Docker from a
> Ubuntu 22.04 host and it successfully takes into account the /sys/fs/cgroup/memory.max
> limit
>
> Even
> Le 26/01/2023 à 02:13, Angus Dickey a écrit :
>
> Even,
>
> Thanks, that is some quick turn around! I imagine Proxmox
> <https://www.proxmox.com/en/> or LXD
> <https://linuxcontainers.org/lxd/introduction/> are pretty much what
> everyone uses to create linux containers. LXC is the underlying technology
> but also has a set of command line tools that can be used to create
> containers. In your case it sounds like LXD can't choose a subnet for your
> linux bridge, which is mysterious and I don't know how to fix that.
>
> I tried your update inside a container and am still seeing the problem
> where GDAL thinks it has the full host memory:
>
> $ gdalinfo --version
> GDAL 3.7.0dev, released 2023/99/99 (debug build)
> $ ./get_gdal_memory
> GDAL version is 3.7.0dev
> GDAL thinks it has 135083474944 bytes of physical memory
> GDAL thinks it has 135083474944 bytes of usable physical memory
> sysinfo() thinks it has 135083474944 bytes of physical memory
> $ free -h
> total used free shared buff/cache
> available
> Mem: 2.0Gi 152Mi 1.1Gi 0.0Ki 755Mi
> 1.8Gi
> Swap: 256Mi 0B 256Mi
> $ cat /proc/meminfo | grep MemTotal
> MemTotal: 2048000 kB
>
> I wanted to dig a bit but am no expert in containerization and cgroup v2.
> It seems that some tools show the memory the container has (free
> <https://man7.org/linux/man-pages/man1/free.1.html>& /proc/meminfo
> <https://man7.org/linux/man-pages/man5/proc.5.html>) and others (sysinfo
> <https://man7.org/linux/man-pages/man2/sysinfo.2.html>) show the host
> memory. For cgroups v2 I see your code is trying to find the max memory
> from a specific memory.max file in /sys/fs/cgroup/. In my *containers *that
> file (actually all the memory.max files) contain the default value "max".
>
> $ find /sys/fs/cgroup -type f -name memory.max -exec sh -c "cat '{}'" \;
> max
> max
> max
> ... all max ...
> max
>
> If I try the same thing on the *host *I actually find it is set to the
> expected value.
>
> cat $ /sys/fs/cgroup/lxc/901/memory.max
> 2097152000
>
> The cgroup values on the host appear to be what is limiting the container
> memory, more rules can be added inside the container but they are still
> beholden to the host rules. I am not sure how free & /proc/memory are
> getting the correct available memory but maybe I will ask the proxmox or
> LXD people.
>
> Thanks again,
>
> Angus
>
>
> On Wed, Jan 25, 2023 at 4:49 AM Even Rouault <even.rouault at spatialys.com>
> wrote:
>
>> Angus,
>>
>> I'm not familiar with LXC. I tried to setup LXD with
>> https://linuxcontainers.org/lxd/introduction/ but it fails with a
>> mysterious "Error: Failed to create local member network "lxdbr0" in
>> project "default": Failed generating auto config: Failed to automatically
>> find an unused IPv4 subnet, manual configuration required"
>>
>> Anyway, I've attempted in https://github.com/OSGeo/gdal/pull/7124 to
>> better take into account cgroup to get memory limitation. Could you give
>> this a try?
>>
>> Even
>> Le 25/01/2023 à 06:24, Angus Dickey a écrit :
>>
>> Even,
>>
>>
>> Thanks for the reply, I went ahead and compiled the latest GDAL 3.6.2 on
>> Ubuntu 22.04. Unfortunately I ended up with a similar result, GDAL thinks
>> it has 755GB of RAM to work with when it only has 2GB:
>>
>>
>> $ gdalinfo --version
>> GDAL 3.6.2, released 2023/01/02 (debug build)
>>
>> $ ./get_gdal_memory
>> GDAL version is 3.6.2
>> GDAL thinks is has 811526475776 bytes of physical memory
>> GDAL thinks it has 811526475776 bytes of usable physical memory
>>
>> $ free -h
>> total used free shared buff/cache
>> available
>> Mem: 2.0Gi 148Mi 1.2Gi 0.0Ki 639Mi
>> 1.8Gi
>> Swap: 256Mi 0B 256Mi
>>
>> My knowledge on the subject is limited but I think Linux containers (LXC)
>> uses cgroups and not setrlimit to limit resources, so maybe that is why the
>> new changes had no effect. To reproduce this issue you can create a
>> container using LXC, LXD, or a hypervision like proxmox (what I am using)
>> and call CPLGetUsablePhysicalRAM().
>>
>> If there is any other info that might be helpful let me know. I might try
>> a Docker container (it also uses cgroups) and is more popular than LXC,
>> although it fulfills a different function.
>>
>> thanks,
>>
>> Angus
>>
>>
>> On Tue, Jan 24, 2023 at 5:50 PM Even Rouault <even.rouault at spatialys.com>
>> wrote:
>>
>>> Angus,
>>>
>>> there has been a recent extra fix that landed in GDAL 3.6.2 that might
>>> possibly help: https://github.com/OSGeo/gdal/pull/6926
>>>
>>> Even
>>> Le 25/01/2023 à 01:36, Angus Dickey a écrit :
>>>
>>> Hi all,
>>>
>>> I am running into an issue where GDAL is overestimating the amount of
>>> physical memory it has leading to it locking up the OS by taking 100% of
>>> the memory. Here is an example program that illustrates the issue:
>>>
>>> #include <stdio.h>
>>> #include "gdal.h"
>>>
>>> int main(void) {
>>> printf("GDAL version is %s\n", GDALVersionInfo("RELEASE_NAME"));
>>> printf("GDAL thinks is has %lld bytes of physical memory\n",
>>> CPLGetPhysicalRAM());
>>> printf("GDAL thinks it has %lld bytes of usable physical memory\n",
>>> CPLGetUsablePhysicalRAM());
>>> return 0;
>>> }
>>>
>>> When this is compiled with GDAL 3.5.1 on Ubuntu 22.04 we get:
>>>
>>> $ ./get_gdal_memory
>>> GDAL version is 3.5.1
>>> GDAL thinks is has 811526475776 bytes of physical memory
>>> GDAL thinks it has 811526475776 bytes of usable physical memory
>>>
>>> Which is not consistent with the actual available memory:
>>>
>>> $ free -h
>>> total used free shared buff/cache
>>> available
>>> Mem: 2.0Gi 148Mi 1.2Gi 0.0Ki 639Mi
>>> 1.8Gi
>>> Swap: 256Mi 0B 256Mi
>>>
>>> So GDAL thinks it has 755GB of memory but it only has 2GB, this causes
>>> issues with the raster read cache and maybe elsewhere. I suspect this is
>>> happening because it is running in a Linux container
>>> <https://linuxcontainers.org/> and GDAL is getting the total physical
>>> memory of the host, not the container. The strange thing is Linux
>>> containers use cgroups for memory restrictions and the API docs mention
>>> it was fixed in GDAL 2.4.0
>>> <https://gdal.org/api/cpl.html#_CPPv417CPLGetPhysicalRAMv> but I am
>>> still seeing the issue in 3.5.1.
>>>
>>> Any help or insight would be appreciated; I am happy to provide any
>>> additional information or testing.
>>>
>>> Thanks,
>>>
>>> Angus
>>>
>>> _______________________________________________
>>> gdal-dev mailing listgdal-dev at lists.osgeo.orghttps://lists.osgeo.org/mailman/listinfo/gdal-dev
>>>
>>> -- http://www.spatialys.com
>>> My software is free, but my time generally not.
>>>
>>> -- http://www.spatialys.com
>> My software is free, but my time generally not.
>>
>> -- http://www.spatialys.com
> My software is free, but my time generally not.
>
>
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