[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] Segments can span multiple clusters with tap:qcow
On 25/4/07 21:41, "Mark McLoughlin" <markmc@xxxxxxxxxx> wrote: > In blktap's qcow we need split up read/write requests if the requests > span multiple clusters. However, with our MAX_AIO_REQUESTS define we > assume that there is only ever a single aio request per tapdisk request > and under heavy i/o we can run out of room causing us to cancel > requests. > > The attached patch dynamically allocates (based on cluster_bits) the > various io request queues the driver maintains. The current code allocates aio-request info for every segment in a request ring (MAX_AIO_REQUESTS == BLK_RING_SIZE * MAX_SEGMENTS_PER_REQUEST). This patch seems to take into account that each segment (part-of-page) can itself be split into clusters, hence the page_size/cluster_size calculation, but shouldn't this be multiplied by the existing MAX_AIO_REQUESTS? Otherwise you provide only enough aio requests for one segment at a time, rather than a request ring's worth of segments? -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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