Date: Tue, 22 Jul 2014 21:42:34 +0400 From: Andrey Chernov <ache@freebsd.org> To: "Pedro F. Giffuni" <pfg@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r268984 - head/lib/libc/stdio Message-ID: <53CEA28A.3040106@freebsd.org> In-Reply-To: <53CE9A77.4060000@freebsd.org> References: <201407221619.s6MGJ10G068003@svn.freebsd.org> <53CE94F6.3090003@freebsd.org> <53CE9A77.4060000@freebsd.org>
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On 22.07.2014 21:08, Andrey Chernov wrote:
> On 22.07.2014 20:44, Andrey Chernov wrote:
>> Producing physical writes on ftell cause great performance degradation.
>> You should check for __SAPP flag before calling sflush to do this only
>> for append-mode files.
>
> BTW, I believe that sflush() should be completely eliminated even for
> _SAPP case. Something like that instead:
Proper patch to the old version:
--- ftell.c.bak 2014-07-22 21:25:46.000000000 +0400
+++ ftell.c 2014-07-22 21:28:01.000000000 +0400
@@ -118,6 +118,11 @@
if (HASUB(fp))
pos -= fp->_r; /* Can be negative at this point. */
} else if ((fp->_flags & __SWR) && fp->_p != NULL) {
+ if (fp->_flags & __SAPP) {
+ pos = _sseek(fp, (fpos_t)0, SEEK_END);
+ if (pos == -1)
+ return (1);
+ }
/*
* Writing. Any buffered characters cause the
* position to be greater than that in the
Forget the code below, it breaks reading:
> if (fp->_flags & __SAPP) {
> pos = _sseek(fp, (fpos_t)0, SEEK_END);
> if (pos == -1)
> return (1);
> } else if (fp->_flags & __SOFF)
> pos = fp->_offset;
> else {
> pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
> if (pos == -1)
> return (1);
> }
>
>>
>> On 22.07.2014 20:19, Pedro F. Giffuni wrote:
>>> Author: pfg
>>> Date: Tue Jul 22 16:19:01 2014
>>> New Revision: 268984
>>> URL: http://svnweb.freebsd.org/changeset/base/268984
>>>
>>> Log:
>>> ftello: return 1 when seeking offset on an append stream.
>>>
>>> Obtained from: Apple Inc. (Libc 997.90.3)
>>> Phabric: D442
>>> MFC after: 2 weeks
>>>
>>> Modified:
>>> head/lib/libc/stdio/ftell.c
>>>
>>> Modified: head/lib/libc/stdio/ftell.c
>>> ==============================================================================
>>> --- head/lib/libc/stdio/ftell.c Tue Jul 22 16:10:56 2014 (r268983)
>>> +++ head/lib/libc/stdio/ftell.c Tue Jul 22 16:19:01 2014 (r268984)
>>> @@ -97,6 +97,8 @@ _ftello(FILE *fp, fpos_t *offset)
>>> * Find offset of underlying I/O object, then
>>> * adjust for buffered bytes.
>>> */
>>> + if (__sflush(fp)) /* may adjust seek offset on append stream */
>>> + return (1);
>>> if (fp->_flags & __SOFF)
>>> pos = fp->_offset;
>>> else {
>>>
>>
>>
>
>
--
http://ache.vniz.net/
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