From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH 2/2] vhost: lockless enqueuing Date: Tue, 26 Apr 2016 15:05:20 +0800 Message-ID: <571F1330.7030504@redhat.com> References: <1461636873-45335-1-git-send-email-jasowang@redhat.com> <1461636873-45335-2-git-send-email-jasowang@redhat.com> <2033086948.46236145.1461651858100.JavaMail.zimbra@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: mst@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Pankaj Gupta Return-path: In-Reply-To: <2033086948.46236145.1461651858100.JavaMail.zimbra@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 04/26/2016 02:24 PM, Pankaj Gupta wrote: > Hi Jason, > > Overall patches look good. Just one doubt I have is below: >> We use spinlock to synchronize the work list now which may cause >> unnecessary contentions. So this patch switch to use llist to remove >> this contention. Pktgen tests shows about 5% improvement: >> >> Before: >> ~1300000 pps >> After: >> ~1370000 pps >> >> Signed-off-by: Jason Wang >> --- >> drivers/vhost/vhost.c | 52 >> +++++++++++++++++++++++++-------------------------- >> drivers/vhost/vhost.h | 7 ++++--- >> 2 files changed, 29 insertions(+), 30 deletions(-) [...] >> - if (work) { >> + node = llist_del_all(&dev->work_list); >> + if (!node) >> + schedule(); >> + >> + node = llist_reverse_order(node); > Can we avoid llist reverse here? > Probably not, this is because: - we should process the work exactly the same order as they were queued, otherwise flush won't work - llist can only add a node to the head of list. Thanks