[Bug libc/1005] New: putc() runs slower

[Bug libc/1005] New: putc() runs slower

[uttamp at us dot ibm dot com]

Bonnie application runs slower with nptl configured glibc library. This
application calls putc() in a tight loop. While using nptl configured libc
(static or dynamic version), causes the worst runtime performance.

-- 
           Summary: putc() runs slower
           Product: glibc
           Version: 2.3.3
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: gotom at debian dot or dot jp
        ReportedBy: uttamp at us dot ibm dot com
                CC: glibc-bugs at sources dot redhat dot com,uttamp at us
                    dot ibm dot com
 GCC build triplet: powerpc-linux
  GCC host triplet: powerpc-linux
GCC target triplet: powerpc-linux


http://sources.redhat.com/bugzilla/show_bug.cgi?id=1005

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[Bug libc/1005] putc() runs slower

[uttamp at us dot ibm dot com]

------- Additional Comments From uttamp at us dot ibm dot com  2005-06-10 21:46 -------
Created an attachment (id=516)
 --> (http://sources.redhat.com/bugzilla/attachment.cgi?id=516&action=view)
Proposed patch


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|gotom at debian dot or dot  |uttamp at us dot ibm dot com
                   |jp                          |
             Status|NEW                         |ASSIGNED


http://sources.redhat.com/bugzilla/show_bug.cgi?id=1005

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[Bug libc/1005] putc() runs slower

[uttamp at us dot ibm dot com]

------- Additional Comments From uttamp at us dot ibm dot com  2005-06-24 22:25 -------
Can this patch be verified?

-- 


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[Bug libc/1005] putc() runs slower

[uttamp at us dot ibm dot com]

------- Additional Comments From uttamp at us dot ibm dot com  2005-07-11 17:46 -------
Created an attachment (id=551)
 --> (http://sources.redhat.com/bugzilla/attachment.cgi?id=551&action=view)
proposed libio-stream lock/unlock patch

patch has added a check in _IO_putc(), _IO_getc(), putchar() and getchar()
library call if the calling app is single threaded or not. If it is single
threaded at the time of call to any of the above call, then call unlocked
version of library functions. This make sense because, when an application (
not multithreaded) calls putc() or any of the above call, thread of executation
is going to remain single, till we come back from the call and execute
pthread_create() and so on. There is no chance of new thread getting created
while application is in any of the above mentioned call. I've built and ran
complete glibc testsuite with the above patch and did not see any new failures
but saw an improvement in the performance numbers (obviously).


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #516 is|0                           |1
           obsolete|                            |


http://sources.redhat.com/bugzilla/show_bug.cgi?id=1005

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[Bug libc/1005] putc() runs slower

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2005-09-23 02:35 -------
This is why there is putc_unlocked.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |WONTFIX


http://sourceware.org/bugzilla/show_bug.cgi?id=1005

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[Bug libc/1005] putc() runs slower

[gsmith at us dot ibm dot com]

------- Additional Comments From gsmith at us dot ibm dot com  2006-02-13 15:26 -------
(In reply to comment #4)
> This is why there is putc_unlocked.

We can't very well advise someone to substitute putc_unlocked() for putc().  
Suppose some sap did this, and then years later the code gets reused in a 
threaded application -- this well-intentioned advice could cause very hard-to-
find problems.

-- 


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