* [dpdk-dev] About the shared flock for hugepage files
@ 2017-09-12 2:16 =?gb18030?B?sNezpMP0?=
2017-09-12 3:10 ` Jim Thompson
0 siblings, 1 reply; 4+ messages in thread
From: =?gb18030?B?sNezpMP0?= @ 2017-09-12 2:16 UTC (permalink / raw)
To: =?gb18030?B?ZGV2?=
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Hi, everyone,
I'm a developer from china, now i have a problem is about the shared flock for hugepage files in the function of "map_all_hugepages()".
as follows:
---------------------------------------------------------------------------------------------------
/* set shared flock on the file. */
if (flock(fd, LOCK_SH | LOCK_NB) == -1) {
RTE_LOG(DEBUG, EAL, "%s(): Locking file failed:%s \n", __func__, strerror(errno));
close(fd);
return i;
}
close(fd);
--------------------------------------------------------------------------------------------------
there, it gives a shared flock to each hugepage file in /mnt/huge, and close it right away.
it makes me puzzled. Why? What doing that is for?
I'm looking forward to your reply, thank you very much.
best regards,
Bakari.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [dpdk-dev] About the shared flock for hugepage files
2017-09-12 2:16 [dpdk-dev] About the shared flock for hugepage files =?gb18030?B?sNezpMP0?=
@ 2017-09-12 3:10 ` Jim Thompson
2017-09-12 3:41 ` [dpdk-dev] =?gb18030?b?u9i4tKO6ICBBYm91dCB0aGUgc2hhcmVkIGZsb2Nr?= =?gb18030?q?_for_hugepage_files?= =?gb18030?B?sNezpMP0?=
0 siblings, 1 reply; 4+ messages in thread
From: Jim Thompson @ 2017-09-12 3:10 UTC (permalink / raw)
To: 白长敏; +Cc: dev
Bakari,
This is so you can have > 1 DPDK application on a machine and they won't use each other's hugepages.
See, for example the comments in clear_hugedir()
http://dpdk.org/browse/dpdk/tree/lib/librte_eal/linuxapp/eal/eal_hugepage_info.c#n198
Jim
> On Sep 11, 2017, at 9:16 PM, 白长敏 <912873551@qq.com> wrote:
>
> Hi, everyone,
>
>
> I'm a developer from china, now i have a problem is about the shared flock for hugepage files in the function of "map_all_hugepages()".
>
>
> as follows:
> ---------------------------------------------------------------------------------------------------
> /* set shared flock on the file. */
>
>
> if (flock(fd, LOCK_SH | LOCK_NB) == -1) {
>
>
> RTE_LOG(DEBUG, EAL, "%s(): Locking file failed:%s \n", __func__, strerror(errno));
>
>
> close(fd);
>
>
> return i;
>
>
> }
>
>
> close(fd);
>
> --------------------------------------------------------------------------------------------------
> there, it gives a shared flock to each hugepage file in /mnt/huge, and close it right away.
>
>
> it makes me puzzled. Why? What doing that is for?
>
>
> I'm looking forward to your reply, thank you very much.
>
>
> best regards,
> Bakari.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [dpdk-dev] =?gb18030?b?u9i4tKO6ICBBYm91dCB0aGUgc2hhcmVkIGZsb2Nr?= =?gb18030?q?_for_hugepage_files?=
2017-09-12 3:10 ` Jim Thompson
@ 2017-09-12 3:41 ` =?gb18030?B?sNezpMP0?=
2017-09-19 14:05 ` [dpdk-dev] 回复: About the shared flock for hugepage files Burakov, Anatoly
0 siblings, 1 reply; 4+ messages in thread
From: =?gb18030?B?sNezpMP0?= @ 2017-09-12 3:41 UTC (permalink / raw)
To: =?gb18030?B?SmltIFRob21wc29u?=; +Cc: =?gb18030?B?ZGV2?=
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="gb18030", Size: 1900 bytes --]
Hi Jim,
Thank you for reply, i understand it, but i still have two doubts.
1) if i have > 1 DPDK application on a machine, i can use the parameter "--file-prefix" to distinguish, it can work even if have not flock.
2) If I understand correctly, in the "map_all_hugepages()", after making the shared flock, close(fd), that is to free the flock. Then, in the "clear_hugedir()", it equal to have not flock ?
------------------ ÔʼÓʼþ ------------------
·¢¼þÈË: "Jim Thompson";<jim@netgate.com>;
·¢ËÍʱ¼ä: 2017Äê9ÔÂ12ÈÕ(ÐÇÆÚ¶þ) ÖÐÎç11:10
ÊÕ¼þÈË: "°×³¤Ãô"<912873551@qq.com>;
³ËÍ: "dev"<dev@dpdk.org>;
Ö÷Ìâ: Re: [dpdk-dev] About the shared flock for hugepage files
Bakari,
This is so you can have > 1 DPDK application on a machine and they won't use each other's hugepages.
See, for example the comments in clear_hugedir()
http://dpdk.org/browse/dpdk/tree/lib/librte_eal/linuxapp/eal/eal_hugepage_info.c#n198
Jim
On Sep 11, 2017, at 9:16 PM, °×³¤Ãô <912873551@qq.com> wrote:
Hi, everyone,
I'm a developer from china, now i have a problem is about the shared flock for hugepage files in the function of "map_all_hugepages()".
as follows:
---------------------------------------------------------------------------------------------------
/* set shared flock on the file. */
if (flock(fd, LOCK_SH | LOCK_NB) == -1) {
RTE_LOG(DEBUG, EAL, "%s(): Locking file failed:%s \n", __func__, strerror(errno));
close(fd);
return i;
}
close(fd);
--------------------------------------------------------------------------------------------------
there, it gives a shared flock to each hugepage file in /mnt/huge, and close it right away.
it makes me puzzled. Why? What doing that is for?
I'm looking forward to your reply, thank you very much.
best regards,
Bakari.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [dpdk-dev] 回复: About the shared flock for hugepage files
2017-09-12 3:41 ` [dpdk-dev] =?gb18030?b?u9i4tKO6ICBBYm91dCB0aGUgc2hhcmVkIGZsb2Nr?= =?gb18030?q?_for_hugepage_files?= =?gb18030?B?sNezpMP0?=
@ 2017-09-19 14:05 ` Burakov, Anatoly
0 siblings, 0 replies; 4+ messages in thread
From: Burakov, Anatoly @ 2017-09-19 14:05 UTC (permalink / raw)
To: 912873551, dev; +Cc: jim
Hi Bakari,
On 12-Sep-17 4:41 AM, 912873551 at qq.com (白长敏) wrote:
> Hi Jim,
>
>
> Thank you for reply, i understand it, but i still have two doubts.
>
>
> 1) if i have > 1 DPDK application on a machine, i can use the parameter "--file-prefix" to distinguish, it can work even if have not flock.
That's not entirely correct. DPDK will attempt to clean up *all*
hugepage files it encounters, not just those that are designated as "its
own" via the --file-prefix [1]. This is because hugepages are not freed
back to the OS unless its backing file in hugetlbfs is removed from the
system, so DPDK needs to clear out any pre-existing hugepage files in
order to successfully allocate any hugepages for its use.
> 2) If I understand correctly, in the "map_all_hugepages()", after making the shared flock, close(fd), that is to free the flock. Then, in the "clear_hugedir()", it equal to have not flock ?
You are correct that normally, closing the file descriptor would release
the lock. However, we're also doing an mmap() call on that fd [2], which
duplicates the descriptor, and therefore we continue to hold a lock to
that file.
Quote from mmap() man page [3]:
"The mmap() function shall add an extra reference to the file associated
with the file descriptor fildes which is not removed by a subsequent
close() on that file descriptor. This reference shall be removed when
there are no more mappings to the file."
[1]
http://www.dpdk.org/browse/dpdk/tree/lib/librte_eal/linuxapp/eal/eal_hugepage_info.c#n192
[2]
http://www.dpdk.org/browse/dpdk/tree/lib/librte_eal/linuxapp/eal/eal_memory.c#n505
[3] https://linux.die.net/man/3/mmap
>
>
> ------------------ ???? ------------------
> ???: "Jim Thompson";<jim at netgate.com>;
> ????: 2017?9?12?(???) ??11:10
> ???: "???"<912873551 at qq.com>;
> ??: "dev"<dev at dpdk.org>;
> ??: Re: [dpdk-dev] About the shared flock for hugepage files
>
>
>
>
> Bakari,
>
>
> This is so you can have > 1 DPDK application on a machine and they won't use each other's hugepages.
>
>
> See, for example the comments in clear_hugedir()
>
>
> http://dpdk.org/browse/dpdk/tree/lib/librte_eal/linuxapp/eal/eal_hugepage_info.c#n198
>
>
> Jim
>
> On Sep 11, 2017, at 9:16 PM, ??? <912873551 at qq.com> wrote:
>
>
> Hi, everyone,
>
>
> I'm a developer from china, now i have a problem is about the shared flock for hugepage files in the function of "map_all_hugepages()".
>
>
> as follows:
> ---------------------------------------------------------------------------------------------------
> /* set shared flock on the file. */
>
>
> if (flock(fd, LOCK_SH | LOCK_NB) == -1) {
>
>
> RTE_LOG(DEBUG, EAL, "%s(): Locking file failed:%s \n", __func__, strerror(errno));
>
>
> close(fd);
>
>
> return i;
>
>
> }
>
>
> close(fd);
>
> --------------------------------------------------------------------------------------------------
> there, it gives a shared flock to each hugepage file in /mnt/huge, and close it right away.
>
>
> it makes me puzzled. Why? What doing that is for?
>
>
> I'm looking forward to your reply, thank you very much.
>
>
> best regards,
> Bakari.
>
--
Thanks,
Anatoly
^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-09-12 2:16 [dpdk-dev] About the shared flock for hugepage files =?gb18030?B?sNezpMP0?=
2017-09-12 3:10 ` Jim Thompson
2017-09-12 3:41 ` [dpdk-dev] =?gb18030?b?u9i4tKO6ICBBYm91dCB0aGUgc2hhcmVkIGZsb2Nr?= =?gb18030?q?_for_hugepage_files?= =?gb18030?B?sNezpMP0?=
2017-09-19 14:05 ` [dpdk-dev] 回复: About the shared flock for hugepage files Burakov, Anatoly
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