From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH v4] vhost: improve dirty pages logging performance Date: Thu, 17 May 2018 14:01:52 +0200 Message-ID: <81a73714-9a7f-0b64-d508-2eb03422fe06@redhat.com> References: <20180517114447.28205-1-maxime.coquelin@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: stable@dpdk.org To: dev@dpdk.org, tiwei.bie@intel.com, mst@redhat.com Return-path: In-Reply-To: <20180517114447.28205-1-maxime.coquelin@redhat.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 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 > Suggested-by: Michael S. Tsirkin > Signed-off-by: Maxime Coquelin I missed to add your: Reviewed-by: Tiwei Bie that you replied to v3, and since the changes in v4 were suggested by you, I guess it still applies. Cheers, Maxime