From: "Wang, Wei W" <wei.w.wang@intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
"jasowang@redhat.com" <jasowang@redhat.com>,
"Stefan Hajnoczi" <stefanha@gmail.com>,
"Marc-André Lureau" <marcandre.lureau@gmail.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"virtio-dev@lists.oasis-open.org"
<virtio-dev@lists.oasis-open.org>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: Jan Scheurich <jan.scheurich@ericsson.com>
Subject: [Qemu-devel] virtio-net: configurable TX queue size
Date: Thu, 4 May 2017 10:58:37 +0000 [thread overview]
Message-ID: <286AC319A985734F985F78AFA26841F7391FDD30@shsmsx102.ccr.corp.intel.com> (raw)
Hi,
I want to re-open the discussion left long time ago:
https://lists.gnu.org/archive/html/qemu-devel/2015-11/msg06194.html
, and discuss the possibility of changing the hardcoded (256) TX queue
size to be configurable between 256 and 1024.
The reason to propose this request is that a severe issue of packet drops in
TX direction was observed with the existing hardcoded 256 queue size,
which causes performance issues for packet drop sensitive guest
applications that cannot use indirect descriptor tables. The issue goes away
with 1K queue size.
The concern mentioned in the previous discussion (please check the link
above) is that the number of chained descriptors would exceed
UIO_MAXIOV (1024) supported by the Linux.
>From the code, I think the number of the chained descriptors is limited to
MAX_SKB_FRAGS + 2 (~18), which is much less than UIO_MAXIOV.
Please point out if I missed anything. Thanks.
Best,
Wei
next reply other threads:[~2017-05-04 10:58 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-04 10:58 Wang, Wei W [this message]
2017-05-05 2:27 ` [Qemu-devel] virtio-net: configurable TX queue size Jason Wang
2017-05-05 5:53 ` [Qemu-devel] [virtio-dev] " Wei Wang
2017-05-05 9:20 ` Jason Wang
2017-05-05 22:08 ` Michael S. Tsirkin
2017-05-07 12:02 ` [Qemu-devel] [virtio-dev] " Yan Vugenfirer
2017-05-08 1:23 ` Wei Wang
2017-05-05 20:36 ` [Qemu-devel] " Michael S. Tsirkin
2017-05-07 4:39 ` Wang, Wei W
2017-05-10 9:00 ` Jason Wang
2017-05-10 9:59 ` Wei Wang
2017-05-10 9:52 ` [Qemu-devel] [virtio-dev] " Wei Wang
2017-05-10 20:07 ` Michael S. Tsirkin
2017-05-11 5:09 ` Wei Wang
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