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Ship it!


- Nathan Binkert


On Aug. 23, 2012, 2:48 a.m., Andreas Hansson wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> http://reviews.gem5.org/r/1321/
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> 
> (Updated Aug. 23, 2012, 2:48 a.m.)
> 
> 
> Review request for Default.
> 
> 
> Description
> -------
> 
> Changeset 9168:571d3ae56173
> ---------------------------
> Clock: Rework clocks to avoid tick-to-cycle transformations
> 
> This patch introduces the notion of a clock update function that aims
> to avoid costly divisions when turning the current tick into a
> cycle. Each clocked object advances a private (hidden) cycle member
> and a tick member and uses these to implement functions for getting
> the tick of the next cycle, or the tick of a cycle some time in the
> future.
> 
> In the different modules using the clocks, changes are made to avoid
> counting in ticks only to later translate to cycles. There are a few
> oddities in how the O3 and inorder CPU count idle cycles, as seen by a
> few locations where a cycle is subtracted in the calculation. This is
> done such that the regression does not change any stats, but should be
> revisited in a future patch.
> 
> Another, much needed, change that is not done as part of this patch is
> to introduce a new typedef uint64_t Cycle to be able to at least hint
> at the unit of the variables counting Ticks vs Cycles. This will be
> done as a follow-up patch.
> 
> As an additional follow up, the thread context still uses ticks for
> the book keeping of last activate and last suspend and this should
> probably also be changed into cycles as well.
> 
> 
> Diffs
> -----
> 
>   src/arch/arm/table_walker.cc 1d983855df2c 
>   src/arch/x86/mmapped_ipr.hh 1d983855df2c 
>   src/cpu/base.cc 1d983855df2c 
>   src/cpu/inorder/cpu.hh 1d983855df2c 
>   src/cpu/inorder/cpu.cc 1d983855df2c 
>   src/cpu/inorder/resource.cc 1d983855df2c 
>   src/cpu/inorder/resource_pool.cc 1d983855df2c 
>   src/cpu/o3/O3CPU.py 1d983855df2c 
>   src/cpu/o3/commit.hh 1d983855df2c 
>   src/cpu/o3/commit_impl.hh 1d983855df2c 
>   src/cpu/o3/cpu.hh 1d983855df2c 
>   src/cpu/o3/cpu.cc 1d983855df2c 
>   src/cpu/o3/fetch_impl.hh 1d983855df2c 
>   src/cpu/o3/inst_queue_impl.hh 1d983855df2c 
>   src/cpu/o3/lsq_unit.hh 1d983855df2c 
>   src/cpu/simple/atomic.cc 1d983855df2c 
>   src/cpu/simple/timing.hh 1d983855df2c 
>   src/cpu/simple/timing.cc 1d983855df2c 
>   src/cpu/testers/memtest/memtest.cc 1d983855df2c 
>   src/cpu/testers/networktest/networktest.cc 1d983855df2c 
>   src/dev/arm/pl111.cc 1d983855df2c 
>   src/dev/i8254xGBe.cc 1d983855df2c 
>   src/dev/ns_gige.cc 1d983855df2c 
>   src/sim/clocked_object.hh 1d983855df2c 
> 
> Diff: http://reviews.gem5.org/r/1321/diff/
> 
> 
> Testing
> -------
> 
> util/regress all passing (disregarding t1000 and eio)
> 
> A minor update. This change did improve performance. Running the
> full regression, including a clean compile of all the ISAs went
> down by 8%. Note that this includes the time for building as well.
> 
> 
> Thanks,
> 
> Andreas Hansson
> 
>

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