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Update comment to clarify the machine spec.

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llvm-svn: 288609
This commit is contained in:
Rui Ueyama
2016-12-04 02:34:29 +00:00
parent 697e7cd761
commit 28f22ae15e
1 changed files with 5 additions and 4 deletions
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9
lld/ELF/Threads.h
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@@ -19,7 +19,8 @@
//
// Fortunately, when a linker links large programs (when the link time is
// most critical), it spends most of the time to work on massive number of
// small pieces of data of the same kind. Here are examples:
// small pieces of data of the same kind, and there are opportunities for
// large parallelism there. Here are examples:
//
// - We have hundreds of thousands of input sections that need to be
// copied to a result file at the last step of link. Once we fix a file
@@ -43,9 +44,9 @@
// The above approach seems to be working fairly well. As an example, when
// linking Chromium (output size 1.6 GB), using 4 cores reduces latency to
// 75% compared to single core (from 12.66 seconds to 9.55 seconds) on my
// machine. Using 40 cores reduces it to 63% (from 12.66 seconds to 7.95
// seconds). Because of the Amdahl's law, the speedup is not linear, but
// as you add more cores, it gets faster.
// Ivy Bridge Xeon 2.8 GHz machine. Using 40 cores reduces it to 63% (from
// 12.66 seconds to 7.95 seconds). Because of the Amdahl's law, the
// speedup is not linear, but as you add more cores, it gets faster.
//
// On a final note, if you are trying to optimize, keep the axiom "don't
// guess, measure!" in mind. Some important passes of the linker are not