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path: root/drivers/hv/ring_buffer.c
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2016-05-01Drivers: hv: vmbus: Implement APIs to support "in place" consumption of ↵K. Y. Srinivasan1-0/+1
vmbus packets Implement APIs for in-place consumption of vmbus packets. Currently, each packet is copied and processed one at a time and as part of processing each packet we potentially may signal the host (if it is waiting for room to produce a packet). These APIs help batched in-place processing of vmbus packets. We also optimize host signaling by having a separate API to signal the end of in-place consumption. With netvsc using these APIs, on an iperf run on average I see about 20X reduction in checks to signal the host. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-05-01Drivers: hv: vmbus: Move some ring buffer functions to hyperv.hK. Y. Srinivasan1-55/+0
In preparation for implementing APIs for in-place consumption of VMBUS packets, movve some ring buffer functionality into hyperv.h Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-05-01Drivers: hv: vmbus: Use the new virt_xx barrier codeK. Y. Srinivasan1-7/+7
Use the virt_xx barriers that have been defined for use in virtual machines. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-05-01Drivers: hv: vmbus: Use READ_ONCE() to read variables that are volatileK. Y. Srinivasan1-3/+3
Use the READ_ONCE macro to access variabes that can change asynchronously. This is the recommended mechanism for dealing with "unsafe" compiler optimizations. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-05-01Drivers: hv: vmbus: Introduce functions for estimating room in the ring bufferK. Y. Srinivasan1-21/+4
Introduce separate functions for estimating how much can be read from and written to the ring buffer. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-05-01Drivers: hv: vmbus: Fix signaling logic in hv_need_to_signal_on_read()K. Y. Srinivasan1-6/+20
On the consumer side, we have interrupt driven flow management of the producer. It is sufficient to base the signaling decision on the amount of space that is available to write after the read is complete. The current code samples the previous available space and uses this in making the signaling decision. This state can be stale and is unnecessary. Since the state can be stale, we end up not signaling the host (when we should) and this can result in a hang. Fix this problem by removing the unnecessary check. I would like to thank Arseney Romanenko <arseneyr@microsoft.com> for pointing out this issue. Also, issue a full memory barrier before making the signaling descision to correctly deal with potential reordering of the write (read index) followed by the read of pending_sz. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Tested-by: Dexuan Cui <decui@microsoft.com> Cc: <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-02-08Drivers: hv: vmbus: Give control over how the ring access is serializedK. Y. Srinivasan1-5/+8
On the channel send side, many of the VMBUS device drivers explicity serialize access to the outgoing ring buffer. Give more control to the VMBUS device drivers in terms how to serialize accesss to the outgoing ring buffer. The default behavior will be to aquire the ring lock to preserve the current behavior. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-02-08Drivers: hv: vmbus: Eliminate the spin lock on the read pathK. Y. Srinivasan1-13/+5
The function hv_ringbuffer_read() is called always on a pre-assigned CPU. Each chnnel is bound to a specific CPU and this function is always called on the CPU the channel is bound. There is no need to acquire the spin lock; get rid of this overhead. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-15Drivers: hv: ring_buffer: eliminate hv_ringbuffer_peek()Vitaly Kuznetsov1-28/+37
Currently, there is only one user for hv_ringbuffer_read()/ hv_ringbuffer_peak() functions and the usage of these functions is: - insecure as we drop ring_lock between them, someone else (in theory only) can acquire it in between; - non-optimal as we do a number of things (acquire/release the above mentioned lock, calculate available space on the ring, ...) twice and this path is performance-critical. Remove hv_ringbuffer_peek() moving the logic from __vmbus_recvpacket() to hv_ringbuffer_read(). Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-15Drivers: hv: ring_buffer: remove code duplication from hv_ringbuffer_peek/read()Vitaly Kuznetsov1-43/+25
hv_ringbuffer_peek() does the same as hv_ringbuffer_read() without advancing the read index. The only functional change this patch brings is moving hv_need_to_signal_on_read() call under the ring_lock but this function is just a couple of comparisons. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-15Drivers: hv: ring_buffer.c: fix comment styleVitaly Kuznetsov1-109/+26
Convert 6+-string comments repeating function names to normal kernel-style comments and fix a couple of other comment style issues. No textual or functional changes intended. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-08-05Drivers: hv_vmbus: Fix signal to host conditionChristopher Oo1-11/+3
Fixes a bug where previously hv_ringbuffer_read would pass in the old number of bytes available to read instead of the expected old read index when calculating when to signal to the host that the ringbuffer is empty. Since the previous write size is already saved, also changes the hv_need_to_signal_on_read to use the previously read value rather than recalculating it. Signed-off-by: Christopher Oo <t-chriso@microsoft.com> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-09-24Drivers: hv: vmbus: Enable interrupt driven flow controlK. Y. Srinivasan1-0/+5
In win8 we have a feature that allows for interrupt driven flow management for host/guest communication. For instance, if the host were blocked because there was no space available in the ringbuffer, the host could request that the guest send an interrupt when space becomes available in the ringbuffer (when the guest drains the ringbuffer). While this feature was implemented in the guest a while ago, we had not advertised that the guest supported this feature. This patch advertises the support to the host. For pre-win8 hosts, this has no effect since the size of the ringbuffer control structure has not changed and all changes have been backward compatible - unused/reserved space has been used to implement this feature. In this version of the patch I have cleaned up the commit log based on feedback from Greg KH. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-02-08Drivers: hv: vmbus: Cleanup the packet send pathK. Y. Srinivasan1-10/+7
The current channel code is using scatterlist abstraction to pass data to the ringbuffer API on the send path. This causes unnecessary translations between virtual and physical addresses. Fix this. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-06-25drivers: hv: check interrupt mask before read_indexJason Wang1-0/+2
This patches add a read barriers to force the driver to check the interrupt mask before read_index. Otherwise we may lost a kick to host. Cc: K. Y. Srinivasan <kys@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-06-18drivers: hv: switch to use mb() instead of smp_mb()Jason Wang1-5/+5
Even if guest were compiled without SMP support, it could not assume that host wasn't. So switch to use mb() instead of smp_mb() to force memory barriers for UP guest. Signed-off-by: Jason Wang <jasowang@redhat.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-04-01Drivers: hv: vmbus: Fix a bug in hv_need_to_signal()K. Y. Srinivasan1-0/+1
As part of updating the vmbus protocol, the function hv_need_to_signal() was introduced. This functions helps optimize signalling from guest to host. The newly added memory barrier is needed to ensure that we correctly decide when to signal the host. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com> Reported-by: Olaf Hering <olh@suse.de> Cc: Stable <stable@vger.kernel.org> (V3.8+) Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-01-17Drivers: hv: Implement flow management on the send sideK. Y. Srinivasan1-1/+50
Implement flow management on the send side. When the sender is blocked, the reader can potentially signal the sender to indicate there is now room to send. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-01-17Drivers: hv: Get rid of hv_get_ringbuffer_interrupt_mask()K. Y. Srinivasan1-13/+0
This function is no longer used; get rid of it. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-01-17Drivers: hv: Optimize the signaling on the write pathK. Y. Srinivasan1-3/+39
The host has already implemented the "read" side optimizations. Leverage that to optimize "write" side signaling. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-01-17Drivers: hv: Implement routines for read side signaling optimizationK. Y. Srinivasan1-0/+24
Implement functions that will support read-side signaling optimization. By having the reader indicate the start of the "read" operation and the "end" of the read operation we can more efficiently handle the signaling protocol: while the read is in progress, there is no need for the "writer" to signal the "reader" as new items are put on the read queue. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-04-04net/hyperv: Add flow control based on hi/low watermarkHaiyang Zhang1-31/+0
In the existing code, we only stop queue when the ringbuffer is full, so the current packet has to be dropped or retried from upper layer. This patch stops the tx queue when available ringbuffer is below the low watermark. So the ringbuffer still has small amount of space available for the current packet. This will reduce the overhead of retries on sending. Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com> Reviewed-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-10-11Staging: hv: remove last user of DPRINT() macroGreg Kroah-Hartman1-31/+0
This also removed the unused function hv_dump_ring_info(). Cc: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2011-10-11Staging: hv: move hyperv code out of staging directoryGreg Kroah-Hartman1-0/+527
After many years wandering the desert, it is finally time for the Microsoft HyperV code to move out of the staging directory. Or at least the core hyperv bus code, and the utility driver, the rest still have some review to get through by the various subsystem maintainers. Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>