Re: [Samba] gencache.tdb size and cache flush
- Date: Tue, 4 Sep 2018 15:36:15 +0200
- From: Francesco Malvezzi via samba <samba@xxxxxxxxxxxxxxx>
- Subject: Re: [Samba] gencache.tdb size and cache flush
Il 04/09/18 12:42, Volker Lendecke ha scritto:
> On Tue, Sep 04, 2018 at 11:59:04AM +0200, Francesco Malvezzi wrote:
>> Il 04/09/18 06:00, Volker Lendecke ha scritto:
>>> Technical description below, but the exec summary is: Yes, we have a
>>> performance problem with gencache.
>>> On Wed, Aug 29, 2018 at 10:28:05AM +0200, Francesco Malvezzi via samba wrote:
>>>> Hi all,
>>>> I have a midsize AD domain with some 50k users but only 100 workstations
>>>> Sometimes I find server CPU throttling at 100%. In order to let it drop
>>> Can you find out where *exactly* that 100% is spent? gstack on the
>>> spinning process with debug symbols would be very helpful here.
>> not sure how to do it.
>> can be like that
> Yes, exactly. The relevant line is
> #19 0x00007fe50c1c5a3c in dcesrv_samr_EnumDomainUsers
thank you for reading all that stuff.
> which means that some client is listing all users in your domain. With
> 50.000 users this takes a while. If the client times out and
> reconnects, this can pretty quickly pile up.
If I simulate it by listing all user in Active Directory User and
Computer utility, I obtain a load raise at 100% cpu, very short because
client disconnects at around 1000 users.
A call to:
time sudo ./bin/ldbsearch -H private/sam.ldb "(objectClass=user)" >
describes better your scenario: one cpu is full load for about 20
seconds and then it drops.
> Do you have Linux clients with winbind and "winbind enum users = yes"
> in your network? This would probably do that to your DC.
As far as I know, the winbindd clients in our milieu do not enumerate
users, unless misconfigured (but can't talk for MacOSX clients),
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