From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>
Subject: Re: [PATCH v4] eal: make hugetlb initialization more
 robust
Date: Wed, 18 May 2016 09:06:52 +0100
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Cc: dev@dpdk.org, david.marchand@6wind.com, nhorman@tuxdriver.com
To: Thomas Monjalon <thomas.monjalon@6wind.com>,
 Jianfeng Tan <jianfeng.tan@intel.com>
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On 17/05/2016 17:40, Thomas Monjalon wrote:
> 2016-05-12 00:44, Jianfeng Tan:
>> This patch adds an option, --huge-trybest, to use a recover mechanism to
>> the case that there are not so many hugepages (declared in sysfs), which
>> can be used. It relys on a mem access to fault-in hugepages, and if fails
> relys -> relies
>
>> with SIGBUS, recover to previously saved stack environment with
>> siglongjmp().
>>
>> Besides, this solution fixes an issue when hugetlbfs is specified with an
>> option of size. Currently DPDK does not respect the quota of a hugetblfs
>> mount. It fails to init the EAL because it tries to map the number of free
>> hugepages in the system rather than using the number specified in the quota
>> for that mount.
> It looks to be a bug. Why adding an option?
> What is the benefit of the old behaviour, not using --try-best?

I do not see any benefit to the old behavior.
Given that we need the signal handling for the cgroup use case, I would 
be inclined to use
this method as the default instead of trying to figure out how many 
hugepages we have free, etc.

Thoughts?

Sergio

>> +static sigjmp_buf jmpenv;
>> +
>> +static void sigbus_handler(int signo __rte_unused)
>> +{
>> +	siglongjmp(jmpenv, 1);
>> +}
>> +
>> +/* Put setjmp into a wrap method to avoid compiling error. Any non-volatile,
>> + * non-static local variable in the stack frame calling sigsetjmp might be
>> + * clobbered by a call to longjmp.
>> + */
>> +static int wrap_sigsetjmp(void)
>> +{
>> +	return sigsetjmp(jmpenv, 1);
>> +}
> Please add the word "huge" to these variables and functions.
>
>> +static struct sigaction action_old;
>> +static int need_recover;
>> +
>> +static void
>> +register_sigbus(void)
>> +{
>> +	sigset_t mask;
>> +	struct sigaction action;
>> +
>> +	sigemptyset(&mask);
>> +	sigaddset(&mask, SIGBUS);
>> +	action.sa_flags = 0;
>> +	action.sa_mask = mask;
>> +	action.sa_handler = sigbus_handler;
>> +
>> +	need_recover = !sigaction(SIGBUS, &action, &action_old);
>> +}
>> +
>> +static void
>> +recover_sigbus(void)
>> +{
>> +	if (need_recover) {
>> +		sigaction(SIGBUS, &action_old, NULL);
>> +		need_recover = 0;
>> +	}
>> +}
> Idem, Please add the word "huge".
>