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SubjectRe: [PATCH 1/3] drivers: hv: vmbus: Introduce latency testing
Date
Branden Bonaby <brandonbonaby94@gmail.com> writes:

> Introduce user specified latency in the packet reception path.
>
> Signed-off-by: Branden Bonaby <brandonbonaby94@gmail.com>
> ---
> drivers/hv/connection.c | 5 +++++
> drivers/hv/ring_buffer.c | 10 ++++++++++
> include/linux/hyperv.h | 14 ++++++++++++++
> 3 files changed, 29 insertions(+)
>
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 09829e15d4a0..2a2c22f5570e 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -354,9 +354,14 @@ void vmbus_on_event(unsigned long data)
> {
> struct vmbus_channel *channel = (void *) data;
> unsigned long time_limit = jiffies + 2;
> + struct vmbus_channel *test_channel = !channel->primary_channel ?
> + channel :
> + channel->primary_channel;
>
> trace_vmbus_on_event(channel);
>
> + if (unlikely(test_channel->fuzz_testing_buffer_delay > 0))
> + udelay(test_channel->fuzz_testing_buffer_delay);
> do {
> void (*callback_fn)(void *);
>
> diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> index 9a03b163cbbd..d7627c9023d6 100644
> --- a/drivers/hv/ring_buffer.c
> +++ b/drivers/hv/ring_buffer.c
> @@ -395,7 +395,12 @@ struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
> {
> struct hv_ring_buffer_info *rbi = &channel->inbound;
> struct vmpacket_descriptor *desc;
> + struct vmbus_channel *test_channel = !channel->primary_channel ?
> + channel :
> + channel->primary_channel;
>
> + if (unlikely(test_channel->fuzz_testing_message_delay > 0))
> + udelay(test_channel->fuzz_testing_message_delay);
> if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
> return NULL;
>
> @@ -420,7 +425,12 @@ __hv_pkt_iter_next(struct vmbus_channel *channel,
> struct hv_ring_buffer_info *rbi = &channel->inbound;
> u32 packetlen = desc->len8 << 3;
> u32 dsize = rbi->ring_datasize;
> + struct vmbus_channel *test_channel = !channel->primary_channel ?
> + channel :
> + channel->primary_channel;

This pattern is repeated 3 times so a define is justified. I would also
reversed the logic:

test_channel = channel->primary_channel ? channel->primary_channel : channel;

>
> + if (unlikely(test_channel->fuzz_testing_message_delay > 0))
> + udelay(test_channel->fuzz_testing_message_delay);

unlikely() is good but if it was under #ifdef it would've been even better.

> /* bump offset to next potential packet */
> rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
> if (rbi->priv_read_index >= dsize)
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index 6256cc34c4a6..8d068956dd67 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -23,6 +23,7 @@
> #include <linux/mod_devicetable.h>
> #include <linux/interrupt.h>
> #include <linux/reciprocal_div.h>
> +#include <linux/delay.h>
>
> #define MAX_PAGE_BUFFER_COUNT 32
> #define MAX_MULTIPAGE_BUFFER_COUNT 32 /* 128K */
> @@ -926,6 +927,19 @@ struct vmbus_channel {
> * full outbound ring buffer.
> */
> u64 out_full_first;
> +
> + /* enabling/disabling fuzz testing on the channel (default is false)*/
> + bool fuzz_testing_state;
> +
> + /* Buffer delay will delay the guest from emptying the ring buffer
> + * for a specific amount of time. The delay is in microseconds and will
> + * be between 1 to a maximum of 1000, its default is 0 (no delay).
> + * The Message delay will delay guest reading on a per message basis
> + * in microseconds between 1 to 1000 with the default being 0
> + * (no delay).
> + */
> + u32 fuzz_testing_buffer_delay;
> + u32 fuzz_testing_message_delay;
> };
>
> static inline bool is_hvsock_channel(const struct vmbus_channel *c)

--
Vitaly

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