If the I/O ring is full, the guest cannot send any more requests
until some responses are sent. Only sending all available responses
just before checking for new work does not leave much time for the
guest to supply new work, so this will cause stalls if the ring gets
full. Also, not completing reads as soon as possible adds latency
to the guest.
To alleviate that, complete IO requests as soon as they come back.
xen_block_send_response() already returns a value indicating whether
a notify should be sent, which is all the batching we need.
Signed-off-by: Tim Smith <tim.smith@citrix.com>
Re-based and commit comment adjusted.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
When I/O consists of many small requests, performance is improved by
batching them together in a single io_submit() call. When there are
relatively few requests, the extra overhead is not worth it. This
introduces a check to start batching I/O requests via blk_io_plug()/
blk_io_unplug() in an amount proportional to the number which were
already in flight at the time we started reading the ring.
Signed-off-by: Tim Smith <tim.smith@citrix.com>
Re-based and commit comment adjusted.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This is a purely cosmetic patch that purges remaining use of 'blk' and
'ioreq' in local function names, and then makes sure all functions are
prefixed with 'xen_block_'.
No functional change.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This is a purely cosmetic patch that purges the name 'ioreq' from struct,
variable and field names. (This name has been problematic for a long time
as 'ioreq' is the name used for generic I/O requests coming from Xen).
The patch replaces 'struct ioreq' with a new 'XenBlockRequest' type and
'ioreq' field/variable names with 'request', and then does necessary
fix-up to adhere to coding style.
Function names are not modified by this patch. They will be dealt with in
a subsequent patch.
No functional change.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This is a purely cosmetic patch that substitutes the old 'struct XenBlkDev'
name with 'XenBlockDataPlane' and 'blkdev' field/variable names with
'dataplane', and then does necessary fix-up to adhere to coding style.
No functional change.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This patch adds the transformations necessary to get dataplane/xen-block.c
to build against the new XenBus/XenDevice framework. MAINTAINERS is also
updated due to the introduction of dataplane/xen-block.h.
NOTE: Existing data structure names are retained for the moment. These will
be modified by subsequent patches. A typedef for XenBlockDataPlane
has been added to the header (based on the old struct XenBlkDev name
for the moment) so that the old names don't need to leak out of the
dataplane code.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Not all of the code duplicated from xen_disk.c is required as the basis for
the new dataplane implementation so this patch removes extraneous code,
along with the legacy #includes and calls to the legacy xen_pv_printf()
function. Error messages are changed to be reported using error_report().
NOTE: The code is still not yet built. Further transformations will be
required to make it correctly interface to the new XenBus/XenDevice
framework. They will be delivered in a subsequent patch.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
The new xen-block XenDevice implementation requires the same core
dataplane as the legacy xen_disk implementation it will eventually replace.
This patch therefore copies the legacy xen_disk.c source module into a new
dataplane/xen-block.c source module as the basis for the new dataplane and
adjusts the MAINTAINERS file accordingly.
NOTE: The duplicated code is not yet built. It is simply put into place by
this patch (just fixing style violations) such that the
modifications that will need to be made to the code are not
conflated with code movement, thus making review harder.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Tim Smith
Paul Durrant