On 27-Feb-19 6:02 PM, Edwin Leung wrote:
Hi Anatoly,
In my test for DPDK 18.11, I notice the following:
1. Using --legacy-mem switch, DPDK still opens 1 fd/huge page. In essence, it
is the same with or without this switch.
2. Using --single-file-segments does reduce the open fd to 1. However, for
each huge page that is in-use, a .lock file is opened. As a result, it still
uses up a large number of fd's.
Thanks.
-- edwin
-----Original Message-----
From: Iain Barker
Sent: Wednesday, February 27, 2019 8:57 AM
To: Burakov, Anatoly <anatoly.bura...@intel.com>; Wiles, Keith
<keith.wi...@intel.com>
Cc: dev@dpdk.org; Edwin Leung <edwin.le...@oracle.com>
Subject: RE: [dpdk-dev] Question about DPDK hugepage fd change
Original Message from: Burakov, Anatoly [mailto:anatoly.bura...@intel.com]
I just realized that, unless you're using --legacy-mem switch, one
other way to alleviate the issue would be to use --single-file-segments
option. This will still store the fd's, however it will only do so per
memseg list, not per page. So, instead of 1000's of fd's with 2MB
pages, you'd end up with under 10. Hope this helps!
Hi Anatoly,
Thanks for the update and suggestion. We did try using --single-file-segments
previously. Although it lowers the amount of fd's allocated for tracking the
segments as you noted, there is still a problem.
It seems that a .lock file is created for each huge page, not for each segment.
So with 2MB pages the glibc limit of 1024 fd's is still exhausted quickly if
there is ~2GB of 2MB huge pages.
Edwin can provide more details from his testing. In our case much sooner, as we
already use >500 fd's for the application, just 1GB of 2MB huge pages is enough
to hit the fd limit due to the .lock files.
Thanks.
Right, i forgot about that. Thanks for noticing! :)
By the way, i've proposed a patch for 19.05 to address this issue. The
downside is that you'd be losing virtio with vhost-user backend support:
http://patches.dpdk.org/patch/50469/
It would be good if you tested it and reported back. Thanks!
(i should fix the wording of the documentation to avoid mentioning
--single-file-segments as a solution - i completely forgot that it
creates lock files...)
--
Thanks,
Anatoly
