From: Jason Wang <jasowang@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org
Subject: Re: [PATCH RFC v1 0/2] vhost: ring format independence
Date: Sat, 12 Oct 2019 16:15:42 +0800 [thread overview]
Message-ID: <f650ac1a-6e2a-9215-6e4f-a1095f4a89cd@redhat.com> (raw)
In-Reply-To: <20191011134358.16912-1-mst@redhat.com>
On 2019/10/11 下午9:45, Michael S. Tsirkin wrote:
> So the idea is as follows: we convert descriptors to an
> independent format first, and process that converting to
> iov later.
>
> The point is that we have a tight loop that fetches
> descriptors, which is good for cache utilization.
> This will also allow all kind of batching tricks -
> e.g. it seems possible to keep SMAP disabled while
> we are fetching multiple descriptors.
I wonder this may help for performance:
- another indirection layer, increased footprint
- won't help or even degrade when there's no batch
- an extra overhead in the case of in order where we should already had
tight loop
- need carefully deal with indirect and chain or make it only work for
packet sit just in a single descriptor
Thanks
>
> And perhaps more importantly, this is a very good fit for the packed
> ring layout, where we get and put descriptors in order.
>
> This patchset seems to already perform exactly the same as the original
> code already based on a microbenchmark. More testing would be very much
> appreciated.
>
> Biggest TODO before this first step is ready to go in is to
> batch indirect descriptors as well.
>
> Integrating into vhost-net is basically
> s/vhost_get_vq_desc/vhost_get_vq_desc_batch/ -
> or add a module parameter like I did in the test module.
>
>
>
> Michael S. Tsirkin (2):
> vhost: option to fetch descriptors through an independent struct
> vhost: batching fetches
>
> drivers/vhost/test.c | 19 ++-
> drivers/vhost/vhost.c | 333 +++++++++++++++++++++++++++++++++++++++++-
> drivers/vhost/vhost.h | 20 ++-
> 3 files changed, 365 insertions(+), 7 deletions(-)
>
next prev parent reply other threads:[~2019-10-12 8:15 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-11 13:45 [PATCH RFC v1 0/2] vhost: ring format independence Michael S. Tsirkin
2019-10-11 13:45 ` [PATCH RFC v1 1/2] vhost: option to fetch descriptors through an independent struct Michael S. Tsirkin
2019-10-12 7:28 ` Jason Wang
2019-10-12 20:27 ` Michael S. Tsirkin
2019-10-14 1:43 ` Jason Wang
2019-10-15 20:20 ` Michael S. Tsirkin
2019-10-16 4:38 ` Jason Wang
2019-10-11 13:46 ` [PATCH RFC v1 2/2] vhost: batching fetches Michael S. Tsirkin
2019-10-12 7:30 ` Jason Wang
2019-10-12 20:36 ` Michael S. Tsirkin
2019-10-14 1:47 ` Jason Wang
2019-10-12 7:31 ` [PATCH RFC v1 0/2] vhost: ring format independence Jason Wang
2019-10-12 20:36 ` Michael S. Tsirkin
2019-10-12 8:15 ` Jason Wang [this message]
2019-10-12 19:26 ` Michael S. Tsirkin
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