upstream/mercurial-mirror Files · contrib/fuzz/fuzzutil.cc

wireprotoframing: buffer emitted data to reduce frame count...

wireprotoframing: buffer emitted data to reduce frame count An upcoming commit introduces a wire protocol command that can emit hundreds of thousands of small objects. Without a buffering layer, we would emit a single, small frame for every object. Performance profiling revealed this to be a source of significant overhead for both client and server. This commit introduces a very crude buffering layer so that we emit fewer, bigger frames in such a scenario. This code will likely get rewritten in the future to be part of the streams API, as we'll need a similar strategy for compressing data. I don't want to think about it too much at the moment though. server before: user 32.500+0.000 sys 1.160+0.000 after: user 20.230+0.010 sys 0.180+0.000 client before: user 133.400+0.000 sys 93.120+0.000 after: user 68.370+0.000 sys 32.950+0.000 This appears to indicate we have significant overhead in the frame processing code on both client and server. It might be worth profiling that at some point... Differential Revision: https://phab.mercurial-scm.org/D4473

Yuya Nishihara - - Load All Authors

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      #include "fuzzutil.h"

      #include <cstring>

      #include <utility>

      contrib::optional<two_inputs> SplitInputs(const uint8_t *Data, size_t Size)

      {

      	if (!Size) {

      		return contrib::nullopt;

      	}

      	// figure out a random point in [0, Size] to split our input.

      	size_t left_size = (Data[0] / 255.0) * (Size - 1);

      	// Copy inputs to new allocations so if bdiff over-reads

      	// AddressSanitizer can detect it.

      	std::unique_ptr<char[]> left(new char[left_size]);

      	std::memcpy(left.get(), Data + 1, left_size);

      	// right starts at the next byte after left ends

      	size_t right_size = Size - (left_size + 1);

      	std::unique_ptr<char[]> right(new char[right_size]);

      	std::memcpy(right.get(), Data + 1 + left_size, right_size);

      	LOG(2) << "inputs are  " << left_size << " and " << right_size

      	       << " bytes" << std::endl;

      	two_inputs result = {std::move(right), right_size, std::move(left),

      	                     left_size};

      	return result;

      }

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				#include "fuzzutil.h"

				#include <cstring>
				#include <utility>

				contrib::optional<two_inputs> SplitInputs(const uint8_t *Data, size_t Size)
				{
				if (!Size) {
				return contrib::nullopt;
				}
				// figure out a random point in [0, Size] to split our input.
				size_t left_size = (Data[0] / 255.0) * (Size - 1);

				// Copy inputs to new allocations so if bdiff over-reads
				// AddressSanitizer can detect it.
				std::unique_ptr<char[]> left(new char[left_size]);
				std::memcpy(left.get(), Data + 1, left_size);
				// right starts at the next byte after left ends
				size_t right_size = Size - (left_size + 1);
				std::unique_ptr<char[]> right(new char[right_size]);
				std::memcpy(right.get(), Data + 1 + left_size, right_size);
				LOG(2) << "inputs are " << left_size << " and " << right_size
				<< " bytes" << std::endl;
				two_inputs result = {std::move(right), right_size, std::move(left),
				left_size};
				return result;
				}