From: Antonio Di Bacco <a.dibacco.ks@gmail.com>
To: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Cc: users@dpdk.org
Subject: Re: Shared memory between two primary DPDK processes
Date: Mon, 18 Apr 2022 19:34:06 +0200 [thread overview]
Message-ID: <CAO8pfFne4OF1caeFf2GE_XagYQJE8OmsSb8F-fWfVQ-KC_bMMQ@mail.gmail.com> (raw)
In-Reply-To: <CAO8pfF=pbNjiXQT1ASpvRnTKfnxCqkxozrbOj8sZnt90QAW-jg@mail.gmail.com>
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At the end I tried the pidfd_getfd syscall that is working really fine and
giving me back a "clone" fd of an fd in that was opened from another
process. I tested it opening a text file in the first process and after
cloning the fd , I could really read the file also in the second process.
Now the weird thing:
1) In the first process I allocate- a huge page, then get the fd
2) In the second process I get my "clone" fd and do an mmap, it works but
if I write on that memory, the first process cannot see what I wrote
int second_process(int remote_pid, int remote_mem_fd) {
printf("remote_pid %d remote_mem_fd %d\n", remote_pid,
remote_mem_fd);
int pidfd = syscall(__NR_pidfd_open, remote_pid, 0);
int my_mem_fd = syscall(438, pidfd, remote_mem_fd, 0);
printf("my_mem_fd %d\n", my_mem_fd); // This is nice
int flags = MAP_SHARED | MAP_HUGETLB | (30 << MAP_HUGE_SHIFT);
uint64_t* addr = (uint64_t*) mmap(NULL, 1024 * 1024 * 1024,
PROT_READ|PROT_WRITE, flags, my_mem_fd, 0);
if (addr == -1)
perror("mmap");
*addr = 0x0101010102020202;
}
Il giorno gio 14 apr 2022 alle ore 21:51 Antonio Di Bacco <
a.dibacco.ks@gmail.com> ha scritto:
>
>
> Il giorno gio 14 apr 2022 alle ore 21:01 Dmitry Kozlyuk <
> dmitry.kozliuk@gmail.com> ha scritto:
>
>> 2022-04-14 10:20 (UTC+0200), Antonio Di Bacco:
>> [...]
>> > Ok, after having a look to memif I managed to exchange the fd between
>> the
>> > two processes and it works.
>> > Anyway the procedure seems a little bit clunky and I think I'm going to
>> use
>> > the new SYSCALL pidfd_getfd
>> > to achieve the same result. In your opinion this method (getfd_pidfd)
>> > could also work if the two DPDK processes
>> > are inside different docker containers?
>>
>> Honestly, I've just learned about pidfd_getfd() from you.
>> But I know that containers use PID namespaces, so there's a question
>> how you will obtain the pidfd of a process in another container.
>>
>> In general, any method of sharing FD will work.
>> Remember that you also need offset and size.
>> Given that some channel is required to share those,
>> I think Unix domain socket is still the preferred way.
>>
>> > Or is there another mechanims like using handles to hugepages present in
>> > the filesystem to share between two
>> > different containers?
>>
>> FD is needed for mmap().
>> You need to either pass the FD or open() the same hugepage file by path.
>> I advise against using paths because they are not a part of DPDK API
>> contract.
>>
>
> Thank you very much Dmitry, your answers are always enlightening.
> I'm going to ask a different question on the dpdk.org about the best
> practice to share memory between two dpdk processes running in different
> containers.
>
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next prev parent reply other threads:[~2022-04-18 17:34 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-08 12:31 Antonio Di Bacco
2022-04-08 13:26 ` Dmitry Kozlyuk
2022-04-08 14:36 ` Ferruh Yigit
2022-04-08 21:14 ` Antonio Di Bacco
2022-04-08 21:08 ` Antonio Di Bacco
2022-04-11 13:03 ` Antonio Di Bacco
2022-04-11 17:30 ` Dmitry Kozlyuk
2022-04-14 8:20 ` Antonio Di Bacco
2022-04-14 19:01 ` Dmitry Kozlyuk
2022-04-14 19:51 ` Antonio Di Bacco
2022-04-18 17:34 ` Antonio Di Bacco [this message]
2022-04-18 17:53 ` Antonio Di Bacco
2022-04-18 19:08 ` Dmitry Kozlyuk
2022-07-06 22:14 ` Antonio Di Bacco
2022-07-07 0:26 ` Dmitry Kozlyuk
2022-07-07 8:48 ` Antonio Di Bacco
2022-07-07 9:26 ` Dmitry Kozlyuk
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