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-rw-r--r--src/system.h90
1 files changed, 45 insertions, 45 deletions
diff --git a/src/system.h b/src/system.h
index dbb4da1ed..eafcc2523 100644
--- a/src/system.h
+++ b/src/system.h
@@ -221,51 +221,6 @@ enum
# endif
#endif
-/* As of Mar 2009, 32KiB is determined to be the minimium
- blksize to best minimize system call overhead.
- This can be tested with this script with the results
- shown for a 1.7GHz pentium-m with 2GB of 400MHz DDR2 RAM:
-
- for i in $(seq 0 10); do
- size=$((8*1024**3)) #ensure this is big enough
- bs=$((1024*2**$i))
- printf "%7s=" $bs
- dd bs=$bs if=/dev/zero of=/dev/null count=$(($size/$bs)) 2>&1 |
- sed -n 's/.* \([0-9.]* [GM]B\/s\)/\1/p'
- done
-
- 1024=734 MB/s
- 2048=1.3 GB/s
- 4096=2.4 GB/s
- 8192=3.5 GB/s
- 16384=3.9 GB/s
- 32768=5.2 GB/s
- 65536=5.3 GB/s
- 131072=5.5 GB/s
- 262144=5.7 GB/s
- 524288=5.7 GB/s
- 1048576=5.8 GB/s
-
- Note that this is to minimize system call overhead.
- Other values may be appropriate to minimize file system
- or disk overhead. For example on my current linux system
- the readahead setting is 128KiB which was read using:
-
- file="."
- device=$(df -P --local "$file" | tail -n1 | cut -d' ' -f1)
- echo $(( $(blockdev --getra $device) * 512 ))
-
- However there isn't a portable way to get the above.
- In the future we could use the above method if available
- and default to io_blksize() if not.
- */
-enum { IO_BUFSIZE = 32*1024 };
-static inline size_t
-io_blksize (struct stat sb)
-{
- return MAX (IO_BUFSIZE, ST_BLKSIZE (sb));
-}
-
/* Redirection and wildcarding when done by the utility itself.
Generally a noop, but used in particular for native VMS. */
#ifndef initialize_main
@@ -701,4 +656,49 @@ bad_cast (char const *s)
return (char *) s;
}
+/* As of Mar 2009, 32KiB is determined to be the minimium
+ blksize to best minimize system call overhead.
+ This can be tested with this script with the results
+ shown for a 1.7GHz pentium-m with 2GB of 400MHz DDR2 RAM:
+
+ for i in $(seq 0 10); do
+ size=$((8*1024**3)) #ensure this is big enough
+ bs=$((1024*2**$i))
+ printf "%7s=" $bs
+ dd bs=$bs if=/dev/zero of=/dev/null count=$(($size/$bs)) 2>&1 |
+ sed -n 's/.* \([0-9.]* [GM]B\/s\)/\1/p'
+ done
+
+ 1024=734 MB/s
+ 2048=1.3 GB/s
+ 4096=2.4 GB/s
+ 8192=3.5 GB/s
+ 16384=3.9 GB/s
+ 32768=5.2 GB/s
+ 65536=5.3 GB/s
+ 131072=5.5 GB/s
+ 262144=5.7 GB/s
+ 524288=5.7 GB/s
+ 1048576=5.8 GB/s
+
+ Note that this is to minimize system call overhead.
+ Other values may be appropriate to minimize file system
+ or disk overhead. For example on my current linux system
+ the readahead setting is 128KiB which was read using:
+
+ file="."
+ device=$(df -P --local "$file" | tail -n1 | cut -d' ' -f1)
+ echo $(( $(blockdev --getra $device) * 512 ))
+
+ However there isn't a portable way to get the above.
+ In the future we could use the above method if available
+ and default to io_blksize() if not.
+ */
+enum { IO_BUFSIZE = 32*1024 };
+static inline size_t
+io_blksize (struct stat sb)
+{
+ return MAX (IO_BUFSIZE, ST_BLKSIZE (sb));
+}
+
void usage (int status) ATTRIBUTE_NORETURN;