>From 1dcd99142e49d3ec7762d657aef868af1fc4d438 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?P=C3=A1draig=20Brady?= Date: Thu, 21 Jul 2011 08:25:49 +0100 Subject: [PATCH] cat,cp,mv,install,split: Set the minimum IO block size used to 64KiB * NEWS: Mention the change in behavior. * src/ioblksize.h: Add updated test results and increase value from 32KiB to 64KiB. --- NEWS | 4 ++++ src/ioblksize.h | 41 +++++++++++++++++++++++------------------ 2 files changed, 27 insertions(+), 18 deletions(-) diff --git a/NEWS b/NEWS index 2952dc9..13a4a25 100644 --- a/NEWS +++ b/NEWS @@ -25,6 +25,10 @@ GNU coreutils NEWS -*- outline -*- ** Changes in behavior + cp,mv,install,cat,split: now read and write a minimum of 64KiB at a time. + This was previously 32KiB and increasing to 64KiB was seen to increase + throughput by 13% when reading cached files on 64 bit GNU/Linux for example. + chmod, chown and chgrp now output the original attributes in messages, when -v or -c specified. diff --git a/src/ioblksize.h b/src/ioblksize.h index eaeced3..d819cf9 100644 --- a/src/ioblksize.h +++ b/src/ioblksize.h @@ -20,30 +20,35 @@ #include "stat-size.h" -/* As of Mar 2009, 32KiB is determined to be the minimium +/* As of Jul 2011, 64KiB 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: + This can be tested with this script: 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' + timeout --foreground -sINT 1 \ + dd bs=$bs if=/dev/zero of=/dev/null 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 + With the results shown for these two systems: + system-1 = 1.7GHz pentium-m with 400MHz DDR2 RAM, arch=i686 + system-2 = 2.1GHz i3-2310M with 1333MHz DDR3 RAM, arch=x86_64 + + blksize system-1 system-2 + ---------------------------- + 1024 734 MB/s 1.7 GB/s + 2048 1.3 GB/s 3.0 GB/s + 4096 2.4 GB/s 5.1 GB/s + 8192 3.5 GB/s 7.3 GB/s + 16384 3.9 GB/s 9.4 GB/s + 32768 5.2 GB/s 9.9 GB/s + 65536 5.3 GB/s 11.2 GB/s + 131072 5.5 GB/s 11.8 GB/s + 262144 5.7 GB/s 11.6 GB/s + 524288 5.7 GB/s 11.4 GB/s + 1048576 5.8 GB/s 11.4 GB/s Note that this is to minimize system call overhead. Other values may be appropriate to minimize file system @@ -58,7 +63,7 @@ In the future we could use the above method if available and default to io_blksize() if not. */ -enum { IO_BUFSIZE = 32*1024 }; +enum { IO_BUFSIZE = 64*1024 }; static inline size_t io_blksize (struct stat sb) { -- 1.7.5.2