Re: [PATCH] mem: warn if address hint is not respected

["Jonas Pfefferle" <pepperjo@japf.ch>]

Hi Xueming,

Correct --base-virtaddr was introduced for that purpose. There are 
multiple reasons why the address layout of the secondary process might 
look different: reasons you mentioned in 2), ASLR etc. I believe there 
is no way to avoid this in real world use cases. The reason for this 
particular patch is that the address hint (--base-virtaddr) is 
sometimes not respected and the kernel falls back to just reserving 
any address it can find to satisfy the mapping (see discussion on the 
patch), i.e. effectively rendering --base-virtaddr useless.

Regards,
Jonas (new email address)


  On Tue, 26 Dec 2017 15:56:10 +0000
  "Xueming(Steven) Li" <xuemingl@mellanox.com> wrote:
> Hi Jonas,
> 
> Seems you are trying to use --base-virtaddr to resolve address 
>conflicts 
> in secondary, I'm wondering how this happened and how to avoid it:
> 1. what's your hugepage side? Hugepage mmap is size aligned, maybe 
>1G works?
> 2. is there more libs loaded in secondary process or memory usage 
>before 
> EAL init?
> 3. Since address allocated in one direction, I'm thinking to reserve 
>a 
> larger "hop" address space as MAP_ANONYMOUS, allocate hugepage, then 
>release 
> "hop". That essentially reserve an address space big enough for 
>secondary,
> and most important the hop size is easy to estimate than 
>--base-virtaddr.
> 
> Thanks,
> Xueming(Steven)
> 
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jonas 
>>Pfefferle1
>> Sent: Wednesday, November 8, 2017 7:52 PM
>> To: Burakov, Anatoly <anatoly.burakov@intel.com>
>> Cc: dev@dpdk.org; jianfeng.tan@intel.com; Thomas Monjalon
>> <thomas@monjalon.net>
>> Subject: Re: [dpdk-dev] [PATCH] mem: warn if address hint is not 
>>respected
>> 
>> "Burakov, Anatoly" <anatoly.burakov@intel.com> wrote on 11/07/2017
>> 02:54:24
>> PM:
>> 
>> > From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
>> > To: Thomas Monjalon <thomas@monjalon.net>
>> > Cc: dev@dpdk.org, Jonas Pfefferle <jpf@zurich.ibm.com>,
>> jianfeng.tan@intel.com
>> > Date: 11/07/2017 02:54 PM
>> > Subject: Re: [dpdk-dev] [PATCH] mem: warn if address hint is not
>> respected
>> >
>> > On 06-Nov-17 8:26 PM, Thomas Monjalon wrote:
>> > > 31/10/2017 10:08, Jonas Pfefferle:
>> > >> Print a warning if the --base-virtaddr hint is not respected 
>>since
>> > >> this might lead to problems when mapping memory in the 
>>secondary
>> > >> process.
>> > >>
>> > >> Signed-off-by: Jonas Pfefferle <jpf@zurich.ibm.com>
>> > >
>> > > Anatoly, please review this patch.
>> > > It does not seem to fix something, so it is candidate for 18.02.
>> > >
>> >
>> > For some reason my Thunderbird ate the original email, so i'll 
>>reply
>> > to this one.
>> >
>> > One nitpick would be that we're calling get_virtual_area many 
>>times
>> > and it would probably be a good idea to make pagesize static and 
>>call
>> > sysconf only once. Otherwise,
>> 
>> We should address this in a separate patch and introduce a pagesize
>> function for everyone to use. sysconf is used like this all over the 
>>place.
>> 
>> >
>> > Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
>> >
>> > --
>> > Thanks,
>> > Anatoly
>> >