linux-kernel - Re: [PATCH net-next 0/6] vhost: accelerate metadata access

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Message-ID: <20190605162631-mutt-send-email-mst@kernel.org>
Date:   Wed, 5 Jun 2019 16:27:18 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        peterx@...hat.com, James.Bottomley@...senpartnership.com,
        hch@...radead.org, davem@...emloft.net, jglisse@...hat.com,
        linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org,
        linux-parisc@...r.kernel.org, christophe.de.dinechin@...il.com,
        jrdr.linux@...il.com
Subject: Re: [PATCH net-next 0/6] vhost: accelerate metadata access

On Fri, May 24, 2019 at 04:12:12AM -0400, Jason Wang wrote:
> Hi:
> 
> This series tries to access virtqueue metadata through kernel virtual
> address instead of copy_user() friends since they had too much
> overheads like checks, spec barriers or even hardware feature
> toggling like SMAP. This is done through setup kernel address through
> direct mapping and co-opreate VM management with MMU notifiers.
> 
> Test shows about 23% improvement on TX PPS. TCP_STREAM doesn't see
> obvious improvement.
> 
> Thanks


Thanks this is queued for next.

Did you want to rebase and repost packed ring support on top?
IIUC it's on par with split ring with these patches.


> Changes from RFC V3:
> - rebase to net-next
> - Tweak on the comments
> Changes from RFC V2:
> - switch to use direct mapping instead of vmap()
> - switch to use spinlock + RCU to synchronize MMU notifier and vhost
>   data/control path
> - set dirty pages in the invalidation callbacks
> - always use copy_to/from_users() friends for the archs that may need
>   flush_dcache_pages()
> - various minor fixes
> Changes from V4:
> - use invalidate_range() instead of invalidate_range_start()
> - track dirty pages
> Changes from V3:
> - don't try to use vmap for file backed pages
> - rebase to master
> Changes from V2:
> - fix buggy range overlapping check
> - tear down MMU notifier during vhost ioctl to make sure
>   invalidation request can read metadata userspace address and vq size
>   without holding vq mutex.
> Changes from V1:
> - instead of pinning pages, use MMU notifier to invalidate vmaps
>   and remap duing metadata prefetch
> - fix build warning on MIPS
> 
> Jason Wang (6):
>   vhost: generalize adding used elem
>   vhost: fine grain userspace memory accessors
>   vhost: rename vq_iotlb_prefetch() to vq_meta_prefetch()
>   vhost: introduce helpers to get the size of metadata area
>   vhost: factor out setting vring addr and num
>   vhost: access vq metadata through kernel virtual address
> 
>  drivers/vhost/net.c   |   4 +-
>  drivers/vhost/vhost.c | 850 ++++++++++++++++++++++++++++++++++++------
>  drivers/vhost/vhost.h |  38 +-
>  3 files changed, 766 insertions(+), 126 deletions(-)
> 
> -- 
> 2.18.1