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    SubjectRe: [PATCH 2/2] vhost: lockless enqueuing
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    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@redhat.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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