On 05-Aug-20 1:58 PM, wangyunjian wrote:
-----Original Message-----
From: Burakov, Anatoly [mailto:anatoly.bura...@intel.com]
Sent: Friday, July 31, 2020 7:55 PM
To: wangyunjian <wangyunj...@huawei.com>; dev@dpdk.org;
david.march...@redhat.com
Cc: Lilijun (Jerry) <jerry.lili...@huawei.com>; xudingke
<xudin...@huawei.com>; sta...@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2] eal/linux: do not create user mem map
repeatedly when it exists
On 30-Jul-20 2:16 PM, wangyunjian wrote:
-----Original Message-----
From: Burakov, Anatoly [mailto:anatoly.bura...@intel.com]
Sent: Monday, July 27, 2020 5:24 PM
To: wangyunjian <wangyunj...@huawei.com>; dev@dpdk.org;
david.march...@redhat.com
Cc: Lilijun (Jerry) <jerry.lili...@huawei.com>; xudingke
<xudin...@huawei.com>; sta...@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2] eal/linux: do not create user mem map
repeatedly when it exists
On 25-Jul-20 10:59 AM, wangyunjian wrote:
-----Original Message-----
From: Burakov, Anatoly [mailto:anatoly.bura...@intel.com]
Sent: Friday, July 24, 2020 9:25 PM
To: wangyunjian <wangyunj...@huawei.com>; dev@dpdk.org;
david.march...@redhat.com
Cc: Lilijun (Jerry) <jerry.lili...@huawei.com>; xudingke
<xudin...@huawei.com>; sta...@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2] eal/linux: do not create user mem
map repeatedly when it exists
On 23-Jul-20 3:48 PM, wangyunjian wrote:
From: Yunjian Wang <wangyunj...@huawei.com>
Currently, we will create new user mem map entry for the same memory
segment, but in fact it has already been added to the user mem maps.
It's not necessary to create it twice.
To resolve the issue, add support to remove the same entry in the
function compact_user_maps().
Fixes: 0cbce3a167f1 ("vfio: skip DMA map failure if already mapped")
Cc: sta...@dpdk.org
Signed-off-by: Yunjian Wang <wangyunj...@huawei.com>
---
v2:
* Remove the same entry in the function compact_user_maps()
---
lib/librte_eal/linux/eal_vfio.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/lib/librte_eal/linux/eal_vfio.c
b/lib/librte_eal/linux/eal_vfio.c index abb12a354..df99307b7 100644
--- a/lib/librte_eal/linux/eal_vfio.c
+++ b/lib/librte_eal/linux/eal_vfio.c
@@ -167,6 +167,10 @@ adjust_map(struct user_mem_map *src,
struct
user_mem_map *end,
static int
merge_map(struct user_mem_map *left, struct user_mem_map
*right)
{
+ /* merge the same maps into one */
+ if (memcmp(left, right, sizeof(struct user_mem_map)) == 0)
+ goto out;
+
merge_map looks for adjacent maps only, but does not handle maps that
are wholly contained within one another ("the same map" also matches
this definition). wouldn't it be better to check for that instead of
*just* handling identical maps?
What about using the initial implementation?
We don't create new user mem map entry for the same memory segment.
I don't like this implementation because it relies on particulars of how VFIO
mapping work without explicitly specifying them. I.e. it's prone to breaking
when changing code. That's not even mentioning that we have no
guarantees
on kernel behavior in that particular case being identical on all supported
platforms.
I would honestly prefer an explicit compaction over implicit one.
What about this implementation?
Again, this works, but i feel like specializing it to just merge the
exact same maps is missing an opportunity to provide a more general
solution that merges same *and* subset maps.
Currently, the problem that I encounter is that a container has many
devices and the application will map the same memory many times.
The kernel driver returns EEXIST as long as there are overlapping memory
areas. Therefore, the application needs to ensure that the memory blocks
of the DMA do not overlap. Otherwise, it will not work normally.
Could you offer me some ideas or advise to fix it？
It sounds like your approach is better if that is indeed the case.
--
Thanks,
Anatoly
