From: Andreas Sandberg <andreas.sandberg@arm.com>
Date: Thu, 21 Jan 2021 12:44:14 +0000 (+0000)
Subject: python: Consistently use ISO prefixes
X-Git-Tag: develop-gem5-snapshot~235
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=ebf29ea90fb1e22381acabd3cacc00a8b8efc230;p=gem5.git

python: Consistently use ISO prefixes

We currently use the traditional SI-like prefixes to represent
binary multipliers in some contexts. This is ambiguous in many cases
since they overload the meaning of the SI prefix.

Here are some examples of commonly used in the industry:
  * Storage vendors define 1 MB as 10**6 bytes
  * Memory vendors define 1 MB as 2**20 bytes
  * Network equipment treats 1Mbit/s as 10**6 bits/s
  * Memory vendors define 1Mbit as 2**20 bits

In practice, this means that a FLASH chip on a storage bus uses
decimal prefixes, but that same flash chip on a memory bus uses binary
prefixes. It would also be reasonable to assume that the contents of a
1Mbit FLASH chip would take 0.1s to transfer over a 10Mbit Ethernet
link. That's however not the case due to different meanings of the
prefix.

The quantity 2MX is treated differently by gem5 depending on the unit
X:

  * Physical quantities (s, Hz, V, A, J, K, C, F) use decimal prefixes.
  * Interconnect and NoC bandwidths (B/s) use binary prefixes.
  * Network bandwidths (bps) use decimal prefixes.
  * Memory sizes and storage sizes (B) use binary prefixes.

Mitigate this ambiguity by consistently using the ISO/IEC/SI prefixes
for binary multipliers for parameters and comments where appropriate.

Change-Id: I3d0bbfa00968486af8d57c36be2c8bee034bae93
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/39577
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
---

diff --git a/src/python/m5/params.py b/src/python/m5/params.py
index 5ff507189..6227fad4c 100644
--- a/src/python/m5/params.py
+++ b/src/python/m5/params.py
@@ -678,7 +678,7 @@ class Float(ParamValue, float):
 
 class MemorySize(CheckedInt):
     cxx_type = 'uint64_t'
-    ex_str = '512MB'
+    ex_str = '512MiB'
     size = 64
     unsigned = True
     def __init__(self, value):
@@ -690,7 +690,7 @@ class MemorySize(CheckedInt):
 
 class MemorySize32(CheckedInt):
     cxx_type = 'uint32_t'
-    ex_str = '512MB'
+    ex_str = '512MiB'
     size = 32
     unsigned = True
     def __init__(self, value):
@@ -710,7 +710,7 @@ class Addr(CheckedInt):
         else:
             try:
                 # Often addresses are referred to with sizes. Ex: A device
-                # base address is at "512MB".  Use toMemorySize() to convert
+                # base address is at "512MiB".  Use toMemorySize() to convert
                 # these into addresses. If the address is not specified with a
                 # "size", an exception will occur and numeric translation will
                 # proceed below.
@@ -1734,7 +1734,7 @@ class NetworkBandwidth(float,ParamValue):
 
 class MemoryBandwidth(float,ParamValue):
     cxx_type = 'float'
-    ex_str = "1GB/s"
+    ex_str = "1GiB/s"
     cmd_line_settable = True
 
     def __new__(cls, value):