[Samba] Samba 4 slow write

[L.P.H. van Belle]

If you want back to samba 3.6.x 
sernet packages..
http://www.enterprisesamba.com/samba-packages/ubuntu/ 


Greetz, 

Louis
 

>-----Oorspronkelijk bericht-----
>Van: airween at gmail.com [mailto:samba-bounces at lists.samba.org] 
>Namens Ervin Hegedüs
>Verzonden: woensdag 22 april 2015 12:44
>Aan: Jones Syue
>CC: samba at lists.samba.org
>Onderwerp: Re: [Samba] Samba 4 slow write
>
>Dear Jones,
>
>many-many thanks for your answers, and for your times...
>
>On Wed, Apr 22, 2015 at 04:50:42PM +0800, Jones Syue wrote:
>> Hello Ervin,
>> ???
>> 
>> > Do you mean that this is the "normal" way? These geteuid and
>> > getegid system calls are so slow?
>> >
>> 
>> >> ???% time     seconds  usecs/call     calls    errors syscall
>> ???>> ???
>> ------ ----------- ----------- --------- --------- ----------------
>> ???>> ???
>>  15.68   15.894980           4   4398791           getegid
>> >> 15.57   15.783699           4   4398801           geteuid???
>> 
>> Hmm yeap
>> ???as earlier mentioned,
>> both system calls are top 2 and more than 30% during compiling.
>> 
>> ???As???
>>  'perf top' call graph depicted,
>> gete{uid, gid} will go through samba stacks, glibc,
>> and syscalls to reach kernel finally,
>> this critical path spent time on stack push-pop, context 
>switches, etc.
>
>yes, that's clear for me,
> 
>> > On the previous system (Debian Wheezy, Samba 3) I've also used
>> > ACL's, but there were much faster than this...
>> >
>> > What should be the solution? Do you have any idea?
>> >
>> 
>> Hmm my guess the difference is made by in-memory cache lookup[1],
>> samba-3 with it.
>> But samba-4 without it,
>> so non-admin users reach gete{uid, gid} heavily,
>> admin users could ease this pain because earlier return by
>> get_current_uid().
>
>ok, this is new for me - but I don't know, what can I do now...
>
>> Here is my test to imply this guess,
>> test-bench is uploading 5,000 files and each one is 1MB.
>> 
>> Case A) samba-3.6.25 without modification,
>> strace show nothing through gete{uid, gid},
>> and spent 85 seconds on uploading.
>> 
>> Case B) Remove cache lookup from samba-3.6.25,
>> strace show syscalls to gete{uid, gid},
>> and spent 100 seconds on uploading.
>
>this isn't a relevant different, the elapsed time increased by
>25% about - but in my case, the elapsed time increased by more,
>that 1000%... (the compile time was about 8 seconds - take a look
>it as 10 secs - on Samba 3, on Samba 4 that's about 100 secs).
>
>So, the big question is what can I do now? There isn't Samba 3
>package in Ubuntu, so I can't downgrade it :(.
>
>
>Thanks,
>
>
>Ervin
>
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