On Feb 9, 2011, at 7:21 PM, Ted Kremenek wrote:
> On Feb 9, 2011, at 6:21 PM, John McCall wrote:
>> On Feb 9, 2011, at 3:56 PM, Ted Kremenek wrote:
>>> Was there a noticeable impact on compile-time? Memory use?
>>
>> "Before my patch" is r125182. "After my patch" is r125185. All
>> measurements except one are the median of 3 approximately similar results as
>> generated on a not-very-reliable, not-hardly-quiescent laptop.
>>
>> Cocoa_h.m creates 35700 Stmts/Exprs and 85258 Decls. On a 64-bit platform,
>> this is a theoretical memory savings of 285,600 bytes for Stmts/Exprs and
>> 682,064 bytes for Decls.
>> - Before my patch, it allocated 13,008,896 bytes, of which it used
>> 12,449,976, with the remainder being lost to e.g. alignment padding.
>> A Release build completed 1000 runs (I'm not sure why I did 1000 runs)
>> on my machine with the following characteristics:
>> daysthatwere:clang rjmccall$ runN 1000 ../../Release/bin/clang
>> -fsyntax-only INPUTS/Cocoa_h.m
>> name avg min med max SD total
>> user 0.3246 0.3215 0.3247 0.3328 0.0014 324.5585
>> sys 0.0771 0.0662 0.0819 0.0898 0.0068 77.1401
>> wall 0.4064 0.3954 0.4088 0.4440 0.0071 406.4173
>>
>> - After my patch, it allocated 12,779,520 bytes, of which it used
>> 12,164,576. This is a memory savings of 284,400 bytes (used). 1,328,392
>> bytes of Stmt/Expr nodes were allocated overall.
>
> The memory savings I see from your numbers is 13,008,896 - 12,779,520 =
> 229,376 (from the total allocated bytes). Isn't this the actual memory
> savings (not 284,400)?
That's a fair point. I was using "used" because there are things we could do
to reduce the overhead from alignment adjustment, whereas there's nothing we
can do to reduce the raw "used" overhead, but in terms of immediate effect on
the compiler, "allocated" is the better number.
John.
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