From: "Xie, Huawei" <huawei.xie@intel.com>
To: "Wang, Zhihong" <zhihong.wang@intel.com>,
Stephen Hemminger <stephen@networkplumber.org>,
"Richardson, Bruce" <bruce.richardson@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [RFC PATCH 2/2] lib/librte_eal: Remove unnecessary hugepage zero-filling
Date: Thu, 19 Nov 2015 06:04:56 +0000 [thread overview]
Message-ID: <C37D651A908B024F974696C65296B57B4B19B621@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <8F6C2BD409508844A0EFC19955BE0941834A76@SHSMSX152.ccr.corp.intel.com>
On 11/19/2015 10:16 AM, Wang, Zhihong wrote:
>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen Hemminger
>> Sent: Thursday, November 19, 2015 3:09 AM
>> To: Richardson, Bruce <bruce.richardson@intel.com>
>> Cc: dev@dpdk.org
>> Subject: Re: [dpdk-dev] [RFC PATCH 2/2] lib/librte_eal: Remove unnecessary
>> hugepage zero-filling
>>
>> On Wed, 18 Nov 2015 16:13:32 +0000
>> "Richardson, Bruce" <bruce.richardson@intel.com> wrote:
>>
>>>
>>>> -----Original Message-----
>>>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen
>>>> Hemminger
>>>> Sent: Wednesday, November 18, 2015 4:00 PM
>>>> To: Xie, Huawei <huawei.xie@intel.com>
>>>> Cc: dev@dpdk.org
>>>> Subject: Re: [dpdk-dev] [RFC PATCH 2/2] lib/librte_eal: Remove
>>>> unnecessary hugepage zero-filling
>>>>
>>>> On Wed, 18 Nov 2015 12:07:54 +0000
>>>> "Xie, Huawei" <huawei.xie@intel.com> wrote:
>>>>
>>>>>>>> The kernel fills new allocated (huge) pages with zeros.
>>>>>>>> DPDK just has to touch the pages to trigger the allocation.
>>>>> I think we shouldn't reply on the assumption that kernel has
>>>>> zeroed the memory. Kernel zeroes the memory mostly to avoid
>>>>> information leakage.It could also achieve this by setting each bit to 1.
>>>>> What we indeed need to check is later DPDK initialization code
>>>>> doesn't assume the memory has been zeroed. Otherwise zero only
>>>>> that part of the memory. Does this makes sense?
>>>> If all new pages are zero, why does DPDK have to pre-touch the pages
>>>> at all?
>>> The pages won't actually be mapped into the processes address space until
>> accessed.
>>> /Bruce
>> Isn't that what mmap MAP_POPULATE flag (not currently used) will do.
> Yes, the MAP_POPULATE does literally the same thing.
> This flag is implemented since Linux 2.5.46 according to Linux man page, guess that's why DPDK fault the page tables manually in the first place. :)
>
> I think we can use this flag since it makes the code clearer.
The manual says MAP_POPULATE is only supported for private mappings
since Linux 2.6.23.
>
> /Zhihong
>
>
next prev parent reply other threads:[~2015-11-19 6:05 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-18 3:27 [dpdk-dev] [RFC PATCH 0/2] Reduce DPDK initialization time Zhihong Wang
2015-11-18 3:27 ` [dpdk-dev] [RFC PATCH 1/2] lib/librte_eal: Reduce timer " Zhihong Wang
2015-11-18 3:27 ` [dpdk-dev] [RFC PATCH 2/2] lib/librte_eal: Remove unnecessary hugepage zero-filling Zhihong Wang
2015-11-18 10:39 ` Mcnamara, John
2015-11-18 10:44 ` Wang, Zhihong
2015-11-18 12:07 ` Xie, Huawei
2015-11-18 16:00 ` Stephen Hemminger
2015-11-18 16:13 ` Richardson, Bruce
2015-11-18 19:09 ` Stephen Hemminger
2015-11-19 2:15 ` Wang, Zhihong
2015-11-19 6:04 ` Xie, Huawei [this message]
2015-11-19 6:32 ` Wang, Zhihong
2015-11-19 9:18 ` Sergio Gonzalez Monroy
2015-11-23 2:54 ` Xie, Huawei
2015-11-23 10:18 ` Bruce Richardson
2015-11-20 12:15 ` Bruce Richardson
2015-11-19 3:54 ` Wang, Zhihong
2015-11-19 6:09 ` Xie, Huawei
2015-11-19 9:14 ` Sergio Gonzalez Monroy
2015-11-23 3:46 ` Xie, Huawei
2015-11-23 4:07 ` Stephen Hemminger
2015-11-23 5:05 ` Xie, Huawei
2015-11-23 6:52 ` Stephen Hemminger
2015-11-25 18:24 ` Xie, Huawei
2015-12-24 8:34 ` [dpdk-dev] [RFC PATCH 0/2] Reduce DPDK initialization time Qiu, Michael
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