Re: [PATCH v4 2/2] tools/xenstore: set open file descriptor limit for xenstored

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 27/09/2021 15:24, Juergen Gross wrote:
> On 27.09.21 16:13, Andrew Cooper wrote:
>> On 27/09/2021 11:48, Juergen Gross wrote:
>>> Add a configuration item for the maximum number of open file
>>> descriptors xenstored should be allowed to have.
>>>
>>> The default should be "unlimited" in order not to restrict xenstored
>>> in the number of domains it can support, but unfortunately the prlimit
>>> command requires specification of a real value for the number of files,
>>> so use 262144 as the default value.
>>
>> Citation needed.
>>
>> prlimit -nunlimited
>>
>> prlimit --nofile=unlimited
>>
>> both work fine, and strace confirms they issue correct system calls.
>
> Not on my test system:
>
> # prlimit --pid 734 --nofile=unlimited
> prlimit: failed to set the NOFILE resource limit: Operation not permitted
> # prlimit --pid 734 --nofile=262144
> #

What does strace say in both of these cases?

>
>> Support for "unlimited" as a parameter has existed for the entire
>> lifetime of the utility,
>> https://github.com/karelzak/util-linux/commit/6bac2825af7216c5471148e219dbcf62ec5ede84
>>
>
> Yes, but not all systems seem to support raising the limit to
> "unlimited".

That's as maybe, but

prlimit64(0, RLIMIT_NOFILE, {rlim_cur=RLIM64_INFINITY,
rlim_max=RLIM64_INFINITY}, NULL) = -1 EPERM (Operation not permitted)

is a Linux issue, not a prlimit bug.

~Andrew