Faster dwarfdump #284
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Faster dwarfdump #284
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Rust's padding code is slow; it writes the padded item to a temporary buffer, measures the length of that buffer to determine how much padding is needed, then writes the padding bytes and the buffered value. When we're just using padding to output a specific number of spaces, we can instead build a string of spaces and print slices of it. Before: time ( target/release/examples/dwarfdump -i ~/mozilla-central/obj-ff-opt/dist/bin/libxul.so >& /dev/null ) real 3m36.962s user 3m35.254s sys 0m1.463s After: time ( target/release/examples/dwarfdump -i ~/mozilla-central/obj-ff-opt/dist/bin/libxul.so >& /dev/null ) real 2m21.745s user 2m20.175s sys 0m1.412s
Using slices of spaces instead of regular padding can speed things up even more, though it's a little more invasive; we need to be able to obtain the value of an enum as a static string to avoid dynamically calculating its length. Before: time ( target/release/examples/dwarfdump -i ~/mozilla-central/obj-ff-opt/dist/bin/libxul.so >& /dev/null ) real 2m21.745s user 2m20.175s sys 0m1.412s After: time ( target/release/examples/dwarfdump -i ~/mozilla-central/obj-ff-opt/dist/bin/libxul.so >& /dev/null ) real 1m39.153s user 1m37.714s sys 0m1.320s
It shouldn't be doing this for |
philipc
reviewed
Mar 4, 2018
| fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { | ||
| match *self { | ||
| impl $struct_name { | ||
| pub fn static_string(&self) -> Option<&'static str> { |
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You could also add something that returns Cow<'static, str> so that the caller can handle the unknown case identically... but then that case doesn't matter much.
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Some simple changes make dwarfdump more than twice as fast.