[Samba] Possible memory leak in

[Matt Oursbourn]

so far I can confirm that with:
aio read size = 0
aio write size = 0

The memory has not grown past 8MiB on any smbd process.

Jeremy, As for the test you suggest.  That is way over my head.  I  don't
understand your email even a little bit.   I am happy to test, but I have
never compiled samba.

-matt



On Tue, Sep 14, 2021 at 11:16 AM Ralph Boehme <slow at samba.org> wrote:

>
> Am 12.09.21 um 21:48 schrieb Matt Oursbourn via samba:
> > What I have noticed from looking at the Processes tab in System
> > Monitor on the server: The server is on a 10GB network.  When I start
> > a chia plot (~106Gb file) transfer from a client computer that is
> > also connected to the 10Gb network the transfer starts off at
> > ~1000Mb/s until the samba process is larger
> than
> > 32.5GiB. The largest I have seen is 39GiB.   The transfer rate then
> > drops down to the hdd write speed of ~170Mb/s.  That samba process
> > never
> gets any
> > smaller than 32.5GiB.  Even after the transfer is complete.
> >
> > If a client computer that is connected with a 1Gb nic starts a
> > transfer, another samba process is spawned. That transfer stays
> > around 130Mb/s
> to 150
> > Mb/s and the samba process grows to ~9GiB. After that transfer is
> > complete the process drops down to ~5MiB.
> >
> > After a day of plotting and transferring ~100 plot files to the
> > server
> from
> > those two computers there are still only the two samba processes
> > running. Plotting has been stopped for several hours  and one is
> > 32.5Gib, the other is 4.9Mib.
>
> the pool-usage of the large process you'd sent me privately contains:
>
> $ grep pthreadpool_tevent_job_state pool-usage\ smbd_32GiB.txt | wc -l
> 6468
>
> which means there are 6468 SMB2 WRITE requests pending at the server.
>
> This is likely triggered because
>
> - the client is sending data much faster then the server is writing data
> to disk
>
> - Samba returns SMB2 Async Interim Response for every received WRITE
> request
>
> - These grant SMB2 credits to the client
>
> - As a result the client is not throttled by a crediting window
>
> Iirc we've seen this before some time ago and iirc a Windows server
> behaves either doesn't send interim async responses or stops sending
> them at some point.
>
> To me this looks like a design flaw in the crediting logic, but we can't
> change that so we have to adjust our write processing code to handle this.
>
> Until that fix materializes (which may take some tim) you could disable
> aio as a workaround in smb.conf by setting:
>
> aio read size = 0
> aio write size = 0
>
> -slow
>
> --
> Ralph Boehme, Samba Team                 https://samba.org/
> SerNet Samba Team Lead      https://sernet.de/en/team-samba
>
>
>
>