Re: [dpdk-dev] [PATCH v4] vhost: improve dirty pages logging performance

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Hi Tiwei,

On 05/17/2018 01:44 PM, Maxime Coquelin wrote:
> This patch caches all dirty pages logging until the used ring index
> is updated.
> 
> The goal of this optimization is to fix a performance regression
> introduced when the vhost library started to use atomic operations
> to set bits in the shared dirty log map. While the fix was valid
> as previous implementation wasn't safe against concurrent accesses,
> contention was induced.
> 
> With this patch, during migration, we have:
> 1. Less atomic operations as only a single atomic OR operation
> per 32 or 64 (depending on CPU) pages.
> 2. Less atomic operations as during a burst, the same page will
> be marked dirty only once.
> 3. Less write memory barriers.
> 
> Fixes: 897f13a1f726 ("vhost: make page logging atomic")
> 
> Cc:stable@dpdk.org
> 
> Cc: Tiwei Bie<tiwei.bie@intel.com>
> Suggested-by: Michael S. Tsirkin<mst@redhat.com>
> Signed-off-by: Maxime Coquelin<maxime.coquelin@redhat.com>

I missed to add your:
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>

that you replied to v3, and since the changes in v4 were suggested by
you, I guess it still applies.

Cheers,
Maxime