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f56dd32bf7
Essentially, the problem is that safemalloc is excruciatingly slow as it checks all allocated blocks for overrun at each memory management primitive, yielding a almost exponential slowdown for the memory management functions (malloc, realloc, free). The overrun check basically consists of verifying some bytes of a block for certain magic keys, which catches some simple forms of overrun. Another minor problem is violation of aliasing rules and that its own internal list of blocks is prone to corruption. Another issue with safemalloc is rather the maintenance cost as the tool has a significant impact on the server code. Given the magnitude of memory debuggers available nowadays, especially those that are provided with the platform malloc implementation, maintenance of a in-house and largely obsolete memory debugger becomes a burden that is not worth the effort due to its slowness and lack of support for detecting more common forms of heap corruption. Since there are third-party tools that can provide the same functionality at a lower or comparable performance cost, the solution is to simply remove safemalloc. Third-party tools can provide the same functionality at a lower or comparable performance cost. The removal of safemalloc also allows a simplification of the malloc wrappers, removing quite a bit of kludge: redefinition of my_malloc, my_free and the removal of the unused second argument of my_free. Since free() always check whether the supplied pointer is null, redudant checks are also removed. Also, this patch adds unit testing for my_malloc and moves my_realloc implementation into the same file as the other memory allocation primitives. client/mysqldump.c: Pass my_free directly as its signature is compatible with the callback type -- which wasn't the case for free_table_ent.
105 lines
2.6 KiB
C++
105 lines
2.6 KiB
C++
/* Copyright (C) 2003 MySQL AB, 2008-2009 Sun Microsystems, Inc
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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#ifdef USE_PRAGMA_IMPLEMENTATION
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#pragma implementation // gcc: Class implementation
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#endif
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#include "sql_priv.h"
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#include <mysql/psi/mysql_file.h>
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#include "transparent_file.h"
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#include "my_sys.h" // MY_WME, MY_ALLOW_ZERO_PTR, MY_SEEK_SET
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Transparent_file::Transparent_file() : lower_bound(0), buff_size(IO_SIZE)
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{
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buff= (uchar *) my_malloc(buff_size*sizeof(uchar), MYF(MY_WME));
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}
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Transparent_file::~Transparent_file()
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{
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my_free(buff);
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}
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void Transparent_file::init_buff(File filedes_arg)
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{
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filedes= filedes_arg;
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/* read the beginning of the file */
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lower_bound= 0;
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mysql_file_seek(filedes, 0, MY_SEEK_SET, MYF(0));
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if (filedes && buff)
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upper_bound= mysql_file_read(filedes, buff, buff_size, MYF(0));
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}
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uchar *Transparent_file::ptr()
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{
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return buff;
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}
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my_off_t Transparent_file::start()
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{
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return lower_bound;
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}
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my_off_t Transparent_file::end()
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{
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return upper_bound;
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}
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my_off_t Transparent_file::read_next()
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{
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size_t bytes_read;
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/*
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No need to seek here, as the file managed by Transparent_file class
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always points to upper_bound byte
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*/
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if ((bytes_read= mysql_file_read(filedes, buff, buff_size, MYF(0)))
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== MY_FILE_ERROR)
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return (my_off_t) -1;
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/* end of file */
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if (!bytes_read)
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return (my_off_t) -1;
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lower_bound= upper_bound;
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upper_bound+= bytes_read;
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return lower_bound;
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}
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char Transparent_file::get_value(my_off_t offset)
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{
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size_t bytes_read;
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/* check boundaries */
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if ((lower_bound <= offset) && (((my_off_t) offset) < upper_bound))
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return buff[offset - lower_bound];
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mysql_file_seek(filedes, offset, MY_SEEK_SET, MYF(0));
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/* read appropriate portion of the file */
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if ((bytes_read= mysql_file_read(filedes, buff, buff_size,
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MYF(0))) == MY_FILE_ERROR)
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return 0;
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lower_bound= offset;
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upper_bound= lower_bound + bytes_read;
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/* end of file */
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if (upper_bound == (my_off_t) offset)
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return 0;
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return buff[0];
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}
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