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Date: Tue, 26 Apr 2016 15:05:20 +0800 From: Jason Wang <jasowang@...hat.com> To: Pankaj Gupta <pagupta@...hat.com> Cc: mst@...hat.com, kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2/2] vhost: lockless enqueuing 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 <jasowang@...hat.com> >> --- >> 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
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