From 6fdf3b21433e901dcba0ac186f00d604ce944f56 Mon Sep 17 00:00:00 2001 From: "K. Y. Srinivasan" Date: Sat, 1 Dec 2012 06:46:32 -0800 Subject: Drivers: hv: Implement routines for read side signaling optimization 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 Reviewed-by: Haiyang Zhang Signed-off-by: Greg Kroah-Hartman --- drivers/hv/ring_buffer.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) (limited to 'drivers/hv/ring_buffer.c') diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index 7233c88f01b8..001079287709 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -29,6 +29,30 @@ #include "hyperv_vmbus.h" +void hv_begin_read(struct hv_ring_buffer_info *rbi) +{ + rbi->ring_buffer->interrupt_mask = 1; + smp_mb(); +} + +u32 hv_end_read(struct hv_ring_buffer_info *rbi) +{ + u32 read; + u32 write; + + rbi->ring_buffer->interrupt_mask = 0; + smp_mb(); + + /* + * Now check to see if the ring buffer is still empty. + * If it is not, we raced and we need to process new + * incoming messages. + */ + hv_get_ringbuffer_availbytes(rbi, &read, &write); + + return read; +} + /* * hv_get_next_write_location() -- cgit v1.2.3 From 98fa8cf4bcc79cb14de8fd815bbcd00dcbd7b20e Mon Sep 17 00:00:00 2001 From: "K. Y. Srinivasan" Date: Sat, 1 Dec 2012 06:46:36 -0800 Subject: Drivers: hv: Optimize the signaling on the write path The host has already implemented the "read" side optimizations. Leverage that to optimize "write" side signaling. Signed-off-by: K. Y. Srinivasan Reviewed-by: Haiyang Zhang Signed-off-by: Greg Kroah-Hartman --- drivers/hv/channel.c | 15 +++++++++------ drivers/hv/hyperv_vmbus.h | 2 +- drivers/hv/ring_buffer.c | 42 +++++++++++++++++++++++++++++++++++++++--- 3 files changed, 49 insertions(+), 10 deletions(-) (limited to 'drivers/hv/ring_buffer.c') diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index 773a2f25a8f0..727c5f1d6acf 100644 --- a/drivers/hv/channel.c +++ b/drivers/hv/channel.c @@ -564,6 +564,7 @@ int vmbus_sendpacket(struct vmbus_channel *channel, const void *buffer, struct scatterlist bufferlist[3]; u64 aligned_data = 0; int ret; + bool signal = false; /* Setup the descriptor */ @@ -580,9 +581,9 @@ int vmbus_sendpacket(struct vmbus_channel *channel, const void *buffer, sg_set_buf(&bufferlist[2], &aligned_data, packetlen_aligned - packetlen); - ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3); + ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal); - if (ret == 0 && !hv_get_ringbuffer_interrupt_mask(&channel->outbound)) + if (ret == 0 && signal) vmbus_setevent(channel); return ret; @@ -606,6 +607,7 @@ int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel, u32 packetlen_aligned; struct scatterlist bufferlist[3]; u64 aligned_data = 0; + bool signal = false; if (pagecount > MAX_PAGE_BUFFER_COUNT) return -EINVAL; @@ -641,9 +643,9 @@ int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel, sg_set_buf(&bufferlist[2], &aligned_data, packetlen_aligned - packetlen); - ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3); + ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal); - if (ret == 0 && !hv_get_ringbuffer_interrupt_mask(&channel->outbound)) + if (ret == 0 && signal) vmbus_setevent(channel); return ret; @@ -665,6 +667,7 @@ int vmbus_sendpacket_multipagebuffer(struct vmbus_channel *channel, u32 packetlen_aligned; struct scatterlist bufferlist[3]; u64 aligned_data = 0; + bool signal = false; u32 pfncount = NUM_PAGES_SPANNED(multi_pagebuffer->offset, multi_pagebuffer->len); @@ -703,9 +706,9 @@ int vmbus_sendpacket_multipagebuffer(struct vmbus_channel *channel, sg_set_buf(&bufferlist[2], &aligned_data, packetlen_aligned - packetlen); - ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3); + ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal); - if (ret == 0 && !hv_get_ringbuffer_interrupt_mask(&channel->outbound)) + if (ret == 0 && signal) vmbus_setevent(channel); return ret; diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h index 3184f6ff4e74..895c898812bd 100644 --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -555,7 +555,7 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info); int hv_ringbuffer_write(struct hv_ring_buffer_info *ring_info, struct scatterlist *sglist, - u32 sgcount); + u32 sgcount, bool *signal); int hv_ringbuffer_peek(struct hv_ring_buffer_info *ring_info, void *buffer, u32 buflen); diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index 001079287709..9bc55f0dcf47 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -53,6 +53,37 @@ u32 hv_end_read(struct hv_ring_buffer_info *rbi) return read; } +/* + * When we write to the ring buffer, check if the host needs to + * be signaled. Here is the details of this protocol: + * + * 1. The host guarantees that while it is draining the + * ring buffer, it will set the interrupt_mask to + * indicate it does not need to be interrupted when + * new data is placed. + * + * 2. The host guarantees that it will completely drain + * the ring buffer before exiting the read loop. Further, + * once the ring buffer is empty, it will clear the + * interrupt_mask and re-check to see if new data has + * arrived. + */ + +static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi) +{ + if (rbi->ring_buffer->interrupt_mask) + return false; + + /* + * This is the only case we need to signal when the + * ring transitions from being empty to non-empty. + */ + if (old_write == rbi->ring_buffer->read_index) + return true; + + return false; +} + /* * hv_get_next_write_location() @@ -322,7 +353,7 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) * */ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, - struct scatterlist *sglist, u32 sgcount) + struct scatterlist *sglist, u32 sgcount, bool *signal) { int i = 0; u32 bytes_avail_towrite; @@ -331,6 +362,7 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, struct scatterlist *sg; u32 next_write_location; + u32 old_write; u64 prev_indices = 0; unsigned long flags; @@ -359,6 +391,8 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, /* Write to the ring buffer */ next_write_location = hv_get_next_write_location(outring_info); + old_write = next_write_location; + for_each_sg(sglist, sg, sgcount, i) { next_write_location = hv_copyto_ringbuffer(outring_info, @@ -375,14 +409,16 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, &prev_indices, sizeof(u64)); - /* Make sure we flush all writes before updating the writeIndex */ - smp_wmb(); + /* Issue a full memory barrier before updating the write index */ + smp_mb(); /* Now, update the write location */ hv_set_next_write_location(outring_info, next_write_location); spin_unlock_irqrestore(&outring_info->ring_lock, flags); + + *signal = hv_need_to_signal(old_write, outring_info); return 0; } -- cgit v1.2.3 From 4fa152ce24724a4a6b2edd26ca2eb7757ff5b2b8 Mon Sep 17 00:00:00 2001 From: "K. Y. Srinivasan" Date: Sat, 1 Dec 2012 06:46:37 -0800 Subject: Drivers: hv: Get rid of hv_get_ringbuffer_interrupt_mask() This function is no longer used; get rid of it. Signed-off-by: K. Y. Srinivasan Reviewed-by: Haiyang Zhang Signed-off-by: Greg Kroah-Hartman --- drivers/hv/hyperv_vmbus.h | 1 - drivers/hv/ring_buffer.c | 13 ------------- 2 files changed, 14 deletions(-) (limited to 'drivers/hv/ring_buffer.c') diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h index 895c898812bd..ac1e419d4b16 100644 --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -565,7 +565,6 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *ring_info, u32 buflen, u32 offset); -u32 hv_get_ringbuffer_interrupt_mask(struct hv_ring_buffer_info *ring_info); void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, struct hv_ring_buffer_debug_info *debug_info); diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index 9bc55f0dcf47..2a0babc95709 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -294,19 +294,6 @@ void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, } } - -/* - * - * hv_get_ringbuffer_interrupt_mask() - * - * Get the interrupt mask for the specified ring buffer - * - */ -u32 hv_get_ringbuffer_interrupt_mask(struct hv_ring_buffer_info *rbi) -{ - return rbi->ring_buffer->interrupt_mask; -} - /* * * hv_ringbuffer_init() -- cgit v1.2.3 From c2b8e5202cf7670f918d0f7439ed2123cd58e1b7 Mon Sep 17 00:00:00 2001 From: "K. Y. Srinivasan" Date: Sat, 1 Dec 2012 06:46:57 -0800 Subject: Drivers: hv: Implement flow management on the send side 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 Reviewed-by: Haiyang Zhang Signed-off-by: Greg Kroah-Hartman --- drivers/hv/channel.c | 12 +++++++++-- drivers/hv/hyperv_vmbus.h | 2 +- drivers/hv/ring_buffer.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++- 3 files changed, 61 insertions(+), 4 deletions(-) (limited to 'drivers/hv/ring_buffer.c') diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index 9303252b2e19..064257e79f23 100644 --- a/drivers/hv/channel.c +++ b/drivers/hv/channel.c @@ -735,6 +735,7 @@ int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer, u32 packetlen; u32 userlen; int ret; + bool signal = false; *buffer_actual_len = 0; *requestid = 0; @@ -761,8 +762,10 @@ int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer, /* Copy over the packet to the user buffer */ ret = hv_ringbuffer_read(&channel->inbound, buffer, userlen, - (desc.offset8 << 3)); + (desc.offset8 << 3), &signal); + if (signal) + vmbus_setevent(channel); return 0; } @@ -779,6 +782,7 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer, u32 packetlen; u32 userlen; int ret; + bool signal = false; *buffer_actual_len = 0; *requestid = 0; @@ -805,7 +809,11 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer, *requestid = desc.trans_id; /* Copy over the entire packet to the user buffer */ - ret = hv_ringbuffer_read(&channel->inbound, buffer, packetlen, 0); + ret = hv_ringbuffer_read(&channel->inbound, buffer, packetlen, 0, + &signal); + + if (signal) + vmbus_setevent(channel); return 0; } diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h index becb106918d6..ac111f223821 100644 --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -550,7 +550,7 @@ int hv_ringbuffer_peek(struct hv_ring_buffer_info *ring_info, void *buffer, int hv_ringbuffer_read(struct hv_ring_buffer_info *ring_info, void *buffer, u32 buflen, - u32 offset); + u32 offset, bool *signal); void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index 2a0babc95709..cafa72ffdc30 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -84,6 +84,50 @@ static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi) return false; } +/* + * To optimize the flow management on the send-side, + * when the sender is blocked because of lack of + * sufficient space in the ring buffer, potential the + * consumer of the ring buffer can signal the producer. + * This is controlled by the following parameters: + * + * 1. pending_send_sz: This is the size in bytes that the + * producer is trying to send. + * 2. The feature bit feat_pending_send_sz set to indicate if + * the consumer of the ring will signal when the ring + * state transitions from being full to a state where + * there is room for the producer to send the pending packet. + */ + +static bool hv_need_to_signal_on_read(u32 old_rd, + struct hv_ring_buffer_info *rbi) +{ + u32 prev_write_sz; + u32 cur_write_sz; + u32 r_size; + u32 write_loc = rbi->ring_buffer->write_index; + u32 read_loc = rbi->ring_buffer->read_index; + u32 pending_sz = rbi->ring_buffer->pending_send_sz; + + /* + * If the other end is not blocked on write don't bother. + */ + if (pending_sz == 0) + return false; + + r_size = rbi->ring_datasize; + cur_write_sz = write_loc >= read_loc ? r_size - (write_loc - read_loc) : + read_loc - write_loc; + + prev_write_sz = write_loc >= old_rd ? r_size - (write_loc - old_rd) : + old_rd - write_loc; + + + if ((prev_write_sz < pending_sz) && (cur_write_sz >= pending_sz)) + return true; + + return false; +} /* * hv_get_next_write_location() @@ -461,13 +505,14 @@ int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info, * */ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer, - u32 buflen, u32 offset) + u32 buflen, u32 offset, bool *signal) { u32 bytes_avail_towrite; u32 bytes_avail_toread; u32 next_read_location = 0; u64 prev_indices = 0; unsigned long flags; + u32 old_read; if (buflen <= 0) return -EINVAL; @@ -478,6 +523,8 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer, &bytes_avail_toread, &bytes_avail_towrite); + old_read = bytes_avail_toread; + /* Make sure there is something to read */ if (bytes_avail_toread < buflen) { spin_unlock_irqrestore(&inring_info->ring_lock, flags); @@ -508,5 +555,7 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer, spin_unlock_irqrestore(&inring_info->ring_lock, flags); + *signal = hv_need_to_signal_on_read(old_read, inring_info); + return 0; } -- cgit v1.2.3