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Improve performance of VirtIO.device_reply

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Switch from using cpu.write8 in a loop to cpu.write_blob. As write8
requires a switch to wasm on every call, it is quite slow.
This commit is contained in:
Fabian 2018-05-02 12:02:42 -05:00
parent d31b424a37
commit 3d60e6f8d2
1 changed files with 10 additions and 19 deletions
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29
src/virtio.js
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@ -337,7 +337,6 @@ VirtIO.prototype.device_reply = function(queueidx, infos)
var next = infos.next;
var desc_start = this.queue_address << 12;
var buffer_idx = 0;
var buffers = [];
do
@ -376,29 +375,21 @@ VirtIO.prototype.device_reply = function(queueidx, infos)
}
while(true);
var buffer_len = -1;
var pointer = 0;
var buffer_idx = 0;
for(var i = 0; i < result_length; i++)
for(var i = 0; i < result_length; )
{
var data = this.device.replybuffer[i];
if(pointer >= buffer_len)
if(buffer_idx === buffers.length)
{
if(buffer_idx === buffers.length)
{
dbg_log("Write more data than descriptor has", LOG_VIRTIO);
return 0;
}
var buf = buffers[buffer_idx++];
addr_low = buf.addr_low;
buffer_len = buf.len;
pointer = 0;
dbg_log("Write more data than descriptor has", LOG_VIRTIO);
return 0;
}
this.cpu.write8(addr_low + pointer++, data);
const buf = buffers[buffer_idx++];
const slice = this.device.replybuffer.subarray(i, i + buf.len);
this.cpu.write_blob(slice, buf.addr_low);
i += buf.len;
}
var used_desc_start = (this.queue_address << 12) + 16 * this.queue_size + 4 + 2 * this.queue_size;