https://bugzilla.novell.com/show_bug.cgi?id=387347 User koenig@linux.de added comment https://bugzilla.novell.com/show_bug.cgi?id=387347#c381873 Summary: pipe uses only 2 CPU on dual-core ("zcat | wc") Product: openSUSE 11.0 Version: Factory Platform: x86-64 OS/Version: Other Status: NEW Severity: Normal Priority: P5 - None Component: Kernel AssignedTo: bnc-team-screening@forge.provo.novell.com ReportedBy: koenig@linux.de QAContact: kernel-maintainers@forge.provo.novell.com Found By: --- as a side result from bug #381873 I got some bad performace for a small pipe on my IBM T60 using intel T7200 core2duo cpu, only one cpu core gets used: harald > zcat /var/lib/pin/ARCHIVES.gz | LC_ALL=C time wc 3331696 30052221 535205599 0:09.43 real, 4.50 user, 0.13 sys, 49% cpu top shows that gzip and wc take about the same about of cpu-time, both around 50%. running xosview shows that CPU0 and CPU1 frequently get changed/used, both show more or less random usage pattern. if I use "zcat | bzip2 > /dev/null" then bzip2 uses 90+ % cpu because it's much more cpu bound... why does "zcat | wc" run "so slow" (doesn't use both CPUs for this pipe) ??? here is the last data for this report for the pipe issue: using "cat" instead of "wc" harald > time zcat /var/lib/pin/ARCHIVES.gz{,,,,,,,} | LC_ALL=C time cat > /dev/null 0:41.11 real, 0.16 user, 1.61 sys, 4% cpu 41.128 0m41.128s real, 37.850 user, 3.148 sys, 99.68 cpu harald > time zcat /var/lib/pin/ARCHIVES.gz{,,,,,,,} | LC_ALL=C time wc > /dev/null 1:16.89 real, 36.23 user, 1.24 sys, 48% cpu 76.902 1m16.902s real, 73.297 user, 2.608 sys, 98.70 cpu NOTE that the 2nd line of time output shows the cpu time sums of the whole pipe (zcat + wc), so wc got 48% cpu and zcat the other 50% harald > uname -a Linux harald 2.6.25-26-default #1 SMP 2008-04-30 07:56:05 +0200 x86_64 x86_64 x86_64 GNU/Linux what's wrong here, why not use both cores ? ;-( -- Configure bugmail: https://bugzilla.novell.com/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.