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virtio: reduce rx allocations when preparing buffers (part 1)

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Instead of returning a vector of buffer chains, return an iterator
range that will produce those vectors on the fly, removing the vector
allocation.
This commit is contained in:
Avi Kivity
2014-10-14 18:05:01 +03:00
parent de4de65d46
commit 7684f00ebe
1 changed files with 7 additions and 6 deletions
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13
net/virtio.cc
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@@ -11,6 +11,7 @@
#include "core/stream.hh"
#include "core/circular_buffer.hh"
#include "core/align.hh"
#include "util/function_input_iterator.hh"
#include <atomic>
#include <vector>
#include <queue>
@@ -488,9 +489,7 @@ virtio_net_device::rxq::prepare_buffers() {
if (available.try_wait(opportunistic)) {
count += opportunistic;
}
std::vector<vring::buffer_chain> vbc;
vbc.reserve(count);
for (unsigned i = 0; i < count; ++i) {
auto make_buffer_chain = [this] {
vring::buffer_chain bc;
std::unique_ptr<char[]> buf(new char[4096]);
vring::buffer b;
@@ -526,9 +525,11 @@ virtio_net_device::rxq::prepare_buffers() {
}
});
bc.push_back(std::move(b));
vbc.push_back(std::move(bc));
}
_ring.post(vbc.begin(), vbc.end());
return bc;
};
auto start = make_function_input_iterator(make_buffer_chain, 0U);
auto finish = make_function_input_iterator(make_buffer_chain, count);
_ring.post(start, finish);
});
}