[sheepdog] [PATCH] sheep: check resource limit at startup

[Liu Yuan]

On 01/29/2013 08:35 AM, MORITA Kazutaka wrote:
> At Mon, 28 Jan 2013 14:47:41 +0800,
> Liu Yuan wrote:
>>
>> From: Liu Yuan <tailai.ly at taobao.com>
>>
>> Sheep daemon is FD hungry and can't survive for EMFILE.
>> 1024 is default for NOFILE on most distributions, which is very
>> dangerous to run Sheepdog cluster. Let's give a warning on this.
>>
>> Signed-off-by: Liu Yuan <tailai.ly at taobao.com>
>> ---
>>  sheep/sheep.c |   29 +++++++++++++++++++++++++++++
>>  1 file changed, 29 insertions(+)
>>
>> diff --git a/sheep/sheep.c b/sheep/sheep.c
>> index f2c7bcd..5c5bcc5 100644
>> --- a/sheep/sheep.c
>> +++ b/sheep/sheep.c
>> @@ -26,6 +26,7 @@
>>  #include <fcntl.h>
>>  #include <errno.h>
>>  #include <arpa/inet.h>
>> +#include <sys/resource.h>
>>  
>>  #include "sheep_priv.h"
>>  #include "trace/trace.h"
>> @@ -385,6 +386,33 @@ static int init_work_queues(void)
>>  	return 0;
>>  }
>>  
>> +#define SD_RLIM_NOFILE 65536
> 
> Please explain why you think 65536 is enough.  Does it an enough
> number even if many VMs send IO requests at the same time?  I've hit
> the FD limitation when doing the test.
>

This is a random value. How about 'unlimited'? Then we don't need to
tweak it later when it is not big enough.


> BTW, Is it difficult to modify sheepdog so that it doesn't use so many
> FDs?
> 

I think yes. Currently the biggest user of FD is sockfd cache and
pusher's push threads, which is performance critical. If we limit the FD
to some ceiling, then I guess we'll lose the performance.

Thanks,
Yuan