Bug 353391 - script wastes quadratic time with /sys/block/sdX/sdXN/slaves
script wastes quadratic time with /sys/block/sdX/sdXN/slaves
Status: CLOSED DUPLICATE of bug 277271
Product: Fedora
Classification: Fedora
Component: mkinitrd (Show other bugs)
All Linux
low Severity low
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Assigned To: Peter Jones
Fedora Extras Quality Assurance
Depends On:
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Reported: 2007-10-25 18:49 EDT by John Reiser
Modified: 2008-03-13 02:19 EDT (History)
0 users

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Doc Type: Bug Fix
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Last Closed: 2008-03-13 02:19:44 EDT
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Attachments (Terms of Use)
summarized strace output involving /sys/block/sdX/sdXN/slaves (6.87 KB, text/plain)
2007-10-25 18:51 EDT, John Reiser
no flags Details

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Description John Reiser 2007-10-25 18:49:32 EDT
Description of problem: During a fresh installation from DVD, two shell scripts
each waste time quadratically in the number of partitions on each harddrive.  On
a box with three drives of (4, 7, 15} partitions, system calls such as
open("/sys/block/sdc/sdc15/slaves", O_RDONLY|O_NONBLOCK|O_DIRECTORY|0x80000) =
 ccount for more than 1% of all system calls during the entire installation.

Version-Release number of selected component (if applicable):

How reproducible: always

Steps to Reproduce:
1. Install on a box that has at least one drive with many partitions.
2. as soon as vtty2 is available:
strace -f -o '|gzip' -p <pid-of-anaconda>  > strace.out &
(you must supply strace on a USB flash drive before boot, and mount the device
3. inspect strace.out (63MB compressed, 1GB uncompressed) for: 
open("/sys/block/sdX/sdXN/slaves", ...) = -1 ENOENT.
Actual results: 142,718 such ENOENT when three drives of 4, 7, 15 partitions. 
(Output will be attached to this bz report.)  All calls come from two /sbin/nash
processes.  There are only 13,238,719 system calls in the whole install.  

Expected results: quadratic algorithms are not allowed when they exceed 1% of
the total effort.

Additional info:
Comment 1 John Reiser 2007-10-25 18:51:40 EDT
Created attachment 238151 [details]
summarized strace output involving /sys/block/sdX/sdXN/slaves

The columns are: count, pid, syscall from strace
Comment 2 Alexandre Oliva 2008-03-13 02:19:44 EDT

*** This bug has been marked as a duplicate of 277271 ***

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