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

[Jonas Pfefferle]

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" <xuemi...@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-boun...@dpdk.org] On Behalf Of Jonas 
Pfefferle1
Sent: Wednesday, November 8, 2017 7:52 PM
To: Burakov, Anatoly <anatoly.bura...@intel.com>
Cc: dev@dpdk.org; jianfeng....@intel.com; Thomas Monjalon
<tho...@monjalon.net>
Subject: Re: [dpdk-dev] [PATCH] mem: warn if address hint is not 
respected

"Burakov, Anatoly" <anatoly.bura...@intel.com> wrote on 11/07/2017
02:54:24
PM:

> From: "Burakov, Anatoly" <anatoly.bura...@intel.com>
> To: Thomas Monjalon <tho...@monjalon.net>
> Cc: dev@dpdk.org, Jonas Pfefferle <j...@zurich.ibm.com>,
jianfeng....@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 <j...@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.bura...@intel.com>
>
> --
> Thanks,
> Anatoly
>