linux-kernel - Re: [RFC V4 PATCH 0/8] Packed ring layout for vhost

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Message-ID: <9a8425be-5c39-eff7-d808-836b825ed890@redhat.com>
Date:   Mon, 21 May 2018 10:33:30 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Wei Xu <wexu@...hat.com>
Cc:     mst@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, jfreimann@...hat.com,
        tiwei.bie@...el.com
Subject: Re: [RFC V4 PATCH 0/8] Packed ring layout for vhost



On 2018年05月21日 00:25, Wei Xu wrote:
> On Wed, May 16, 2018 at 08:32:13PM +0800, Jason Wang wrote:
>> Hi all:
>>
>> This RFC implement packed ring layout. The code were tested with
>> Tiwei's RFC V3 ahttps://lkml.org/lkml/2018/4/25/34. Some fixups and
>> tweaks were needed on top of Tiwei's code to make it run for event
>> index.
> Could you please show the change based on Tiwei's code to easy other's
> test?

Please try Tiwei's V4 instead of just waiting for the fixup. It should 
work unless you don't try zerocopy and vIOMMU.


>> Pktgen reports about 20% improvement on PPS (event index is off). More
>> testing is ongoing.
>>
>> Notes for tester:
>>
>> - Start from this version, vhost need qemu co-operation to work
>>    correctly. Or you can comment out the packed specific code for
>>    GET/SET_VRING_BASE.
> Do you mean the code in vhost_virtqueue_start/stop?

For qemu, probably.

> Both Tiwei's and your v3
> work fortunately correctly which should be avoided since the ring should be
> definitely different.

I don't understand this, you mean reset work?

Thanks

>
> Wei
>
>> Changes from V3:
>> - Fix math on event idx checking
>> - Sync last avail wrap counter through GET/SET_VRING_BASE
>> - remove desc_event prefix in the driver/device structure
>>
>> Changes from V2:
>> - do not use & in checking desc_event_flags
>> - off should be most significant bit
>> - remove the workaround of mergeable buffer for dpdk prototype
>> - id should be in the last descriptor in the chain
>> - keep _F_WRITE for write descriptor when adding used
>> - device flags updating should use ADDR_USED type
>> - return error on unexpected unavail descriptor in a chain
>> - return false in vhost_ve_avail_empty is descriptor is available
>> - track last seen avail_wrap_counter
>> - correctly examine available descriptor in get_indirect_packed()
>> - vhost_idx_diff should return u16 instead of bool
>>
>> Changes from V1:
>>
>> - Refactor vhost used elem code to avoid open coding on used elem
>> - Event suppression support (compile test only).
>> - Indirect descriptor support (compile test only).
>> - Zerocopy support.
>> - vIOMMU support.
>> - SCSI/VSOCK support (compile test only).
>> - Fix several bugs
>>
>> Jason Wang (8):
>>    vhost: move get_rx_bufs to vhost.c
>>    vhost: hide used ring layout from device
>>    vhost: do not use vring_used_elem
>>    vhost_net: do not explicitly manipulate vhost_used_elem
>>    vhost: vhost_put_user() can accept metadata type
>>    virtio: introduce packed ring defines
>>    vhost: packed ring support
>>    vhost: event suppression for packed ring
>>
>>   drivers/vhost/net.c                | 136 ++----
>>   drivers/vhost/scsi.c               |  62 +--
>>   drivers/vhost/vhost.c              | 861 ++++++++++++++++++++++++++++++++-----
>>   drivers/vhost/vhost.h              |  47 +-
>>   drivers/vhost/vsock.c              |  42 +-
>>   include/uapi/linux/virtio_config.h |   9 +
>>   include/uapi/linux/virtio_ring.h   |  32 ++
>>   7 files changed, 928 insertions(+), 261 deletions(-)
>>
>> -- 
>> 2.7.4
>>