From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: Yongseok Koh <yskoh@mellanox.com>,
"Walker, Benjamin" <benjamin.walker@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"thomas@monjalon.net" <thomas@monjalon.net>,
"andras.kovacs@ericsson.com" <andras.kovacs@ericsson.com>,
"Wiles, Keith" <keith.wiles@intel.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>
Subject: Re: [dpdk-dev] [RFC v2 00/23] Dynamic memory allocation for DPDK
Date: Mon, 5 Feb 2018 10:03:35 +0000 [thread overview]
Message-ID: <afbeaf2a-3d5b-544e-d6ae-0d6b6d2f6023@intel.com> (raw)
In-Reply-To: <20180202192832.GA42096@yongseok-MBP.local>
On 02-Feb-18 7:28 PM, Yongseok Koh wrote:
> On Tue, Dec 26, 2017 at 05:19:25PM +0000, Walker, Benjamin wrote:
>> On Fri, 2017-12-22 at 09:13 +0000, Burakov, Anatoly wrote:
>>> On 21-Dec-17 9:38 PM, Walker, Benjamin wrote:
>>>> SPDK will need some way to register for a notification when pages are
>>>> allocated
>>>> or freed. For storage, the number of requests per second is (relative to
>>>> networking) fairly small (hundreds of thousands per second in a traditional
>>>> block storage stack, or a few million per second with SPDK). Given that, we
>>>> can
>>>> afford to do a dynamic lookup from va to pa/iova on each request in order to
>>>> greatly simplify our APIs (users can just pass pointers around instead of
>>>> mbufs). DPDK has a way to lookup the pa from a given va, but it does so by
>>>> scanning /proc/self/pagemap and is very slow. SPDK instead handles this by
>>>> implementing a lookup table of va to pa/iova which we populate by scanning
>>>> through the DPDK memory segments at start up, so the lookup in our table is
>>>> sufficiently fast for storage use cases. If the list of memory segments
>>>> changes,
>>>> we need to know about it in order to update our map.
>>>
>>> Hi Benjamin,
>>>
>>> So, in other words, we need callbacks on alloa/free. What information
>>> would SPDK need when receiving this notification? Since we can't really
>>> know in advance how many pages we allocate (it may be one, it may be a
>>> thousand) and they no longer are guaranteed to be contiguous, would a
>>> per-page callback be OK? Alternatively, we could have one callback per
>>> operation, but only provide VA and size of allocated memory, while
>>> leaving everything else to the user. I do add a virt2memseg() function
>>> which would allow you to look up segment physical addresses easier, so
>>> you won't have to manually scan memseg lists to get IOVA for a given VA.
>>>
>>> Thanks for your feedback and suggestions!
>>
>> Yes - callbacks on alloc/free would be perfect. Ideally for us we want one
>> callback per virtual memory region allocated, plus a function we can call to
>> find the physical addresses/page break points on that virtual region. The
>> function that finds the physical addresses does not have to be efficient - we'll
>> just call that once when the new region is allocated and store the results in a
>> fast lookup table. One call per virtual region is better for us than one call
>> per physical page because we're actually keeping multiple different types of
>> memory address translation tables in SPDK. One translates from va to pa/iova, so
>> for this one we need to break this up into physical pages and it doesn't matter
>> if you do one call per virtual region or one per physical page. However another
>> one translates from va to RDMA lkey, so it is much more efficient if we can
>> register large virtual regions in a single call.
>
> Another yes to callbacks. Like Benjamin mentioned about RDMA, MLX PMD has to
> look up LKEY per each packet DMA. Let me briefly explain about this for your
> understanding. For security reason, we don't allow application initiates a DMA
> transaction with unknown random physical addresses. Instead, va-to-pa mapping
> (we call it Memory Region) should be pre-registered and LKEY is the index of the
> translation entry registered in device. With the current static memory model, it
> is easy to manage because v-p mapping is unchanged over time. But if it becomes
> dynamic, MLX PMD should get notified with the event to register/un-regsiter
> Memory Region.
>
> For MLX PMD, it is also enough to get one notification per allocation/free of a
> virutal memory region. It shouldn't necessarily be a per-page call like Benjamin
> mentioned because PA of region doesn't need to be contiguous for registration.
> But it doesn't need to know about physical address of the region (I'm not saying
> it is unnecessary, but just FYI :-).
>
> Thanks,
> Yongseok
>
Thanks for your feedback, good to hear we're on the right track. I
already have a prototype implementation of this working, due for v1
submission :)
--
Thanks,
Anatoly
next prev parent reply other threads:[~2018-02-05 10:03 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-19 11:14 Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 01/23] eal: move get_virtual_area out of linuxapp eal_memory.c Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 02/23] eal: add function to report number of detected sockets Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 03/23] eal: add rte_fbarray Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 04/23] eal: move all locking to heap Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 05/23] eal: protect malloc heap stats with a lock Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 06/23] eal: make malloc a doubly-linked list Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 07/23] eal: make malloc_elem_join_adjacent_free public Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 08/23] eal: add "single file segments" command-line option Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 09/23] eal: add "legacy memory" option Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 10/23] eal: read hugepage counts from node-specific sysfs path Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 11/23] eal: replace memseg with memseg lists Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 12/23] eal: add support for dynamic memory allocation Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 13/23] eal: make use of dynamic memory allocation for init Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 14/23] eal: add support for dynamic unmapping of pages Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 15/23] eal: add API to check if memory is physically contiguous Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 16/23] eal: enable dynamic memory allocation/free on malloc/free Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 17/23] eal: add backend support for contiguous memory allocation Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 18/23] eal: add rte_malloc support for allocating contiguous memory Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 19/23] eal: enable reserving physically contiguous memzones Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 20/23] eal: make memzones use rte_fbarray Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 21/23] mempool: add support for the new memory allocation methods Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 22/23] vfio: allow to map other memory regions Anatoly Burakov
2017-12-19 11:14 ` [dpdk-dev] [RFC v2 23/23] eal: map/unmap memory with VFIO when alloc/free pages Anatoly Burakov
2017-12-19 15:46 ` [dpdk-dev] [RFC v2 00/23] Dynamic memory allocation for DPDK Stephen Hemminger
2017-12-19 16:02 ` Burakov, Anatoly
2017-12-19 16:06 ` Stephen Hemminger
2017-12-19 16:09 ` Burakov, Anatoly
2017-12-21 21:38 ` Walker, Benjamin
2017-12-22 9:13 ` Burakov, Anatoly
2017-12-26 17:19 ` Walker, Benjamin
2018-02-02 19:28 ` Yongseok Koh
2018-02-05 10:03 ` Burakov, Anatoly [this message]
2018-02-05 10:18 ` Nélio Laranjeiro
2018-02-05 10:36 ` Burakov, Anatoly
2018-02-06 9:10 ` Nélio Laranjeiro
2018-02-14 2:01 ` Yongseok Koh
2018-02-14 9:32 ` Burakov, Anatoly
2018-02-14 18:13 ` Yongseok Koh
2018-01-13 14:13 ` Burakov, Anatoly
2018-01-23 22:33 ` Yongseok Koh
2018-01-25 16:18 ` Burakov, Anatoly
2018-02-14 8:04 ` Thomas Monjalon
2018-02-14 10:07 ` Burakov, Anatoly
2018-04-25 16:02 ` Burakov, Anatoly
2018-04-25 16:12 ` Stephen Hemminger
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