[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2] 9p/xen: increase XEN_9PFS_RING_ORDER
n Fri, 22 May 2020, Dominique Martinet wrote: > Stefano Stabellini wrote on Thu, May 21, 2020: > > From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx> > > > > Increase XEN_9PFS_RING_ORDER to 9 for performance reason. Order 9 is the > > max allowed by the protocol. > > > > We can't assume that all backends will support order 9. The xenstore > > property max-ring-page-order specifies the max order supported by the > > backend. We'll use max-ring-page-order for the size of the ring. > > > > This means that the size of the ring is not static > > (XEN_FLEX_RING_SIZE(9)) anymore. Change XEN_9PFS_RING_SIZE to take an > > argument and base the calculation on the order chosen at setup time. > > > > Finally, modify p9_xen_trans.maxsize to be divided by 4 compared to the > > original value. We need to divide it by 2 because we have two rings > > coming off the same order allocation: the in and out rings. This was a > > mistake in the original code. Also divide it further by 2 because we > > don't want a single request/reply to fill up the entire ring. There can > > be multiple requests/replies outstanding at any given time and if we use > > the full ring with one, we risk forcing the backend to wait for the > > client to read back more replies before continuing, which is not > > performant. > > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx> > > LGTM, I'll try to find some time to test this by the end of next week or > will trust you if I can't make it -- ping me around June 1st if I don't > reply again until then... Ping :-)
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