417660449f
sds type should be determined based on the size of the underlying buffer, not the logical length of the sds. Currently we truncate the alloc field in case buffer is larger than we can handle. It leads to a mismatch between alloc field and the actual size of the buffer. Even considering that alloc doesn't include header size and the null terminator. It also leads to a waste of memory with jemalloc. For example, let's consider creation of sds of length 253. According to the length, the appropriate type is SDS_TYPE_8. But we allocate `253 + sizeof(struct sdshdr8) + 1` bytes, which sums to 257 bytes. In this case jemalloc allocates buffer from the next size bucket. With current configuration on Linux it's 320 bytes. So we end up with 320 bytes buffer, while we can't address more than 255. The same happens with other types and length close enough to the appropriate powers of 2. The downside of the adjustment is that with allocators that do not allocate larger than requested chunks (like GNU allocator), we switch to a larger type "too early". It leads to small waste of memory. Specifically: sds of length 31 takes 35 bytes instead of 33 (2 bytes wasted) sds of length 255 takes 261 bytes instead of 259 (2 bytes wasted) sds of length 65,535 takes 65,545 bytes instead of 65,541 (4 bytes wasted) sds of length 4,294,967,295 takes 4,294,967,313 bytes instead of 4,294,967,305 (8 bytes wasted) --------- Signed-off-by: Vadym Khoptynets <vadymkh@amazon.com>
55 lines
2.4 KiB
C
55 lines
2.4 KiB
C
/* SDSLib 2.0 -- A C dynamic strings library
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*
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* Copyright (c) 2006-2015, Salvatore Sanfilippo <antirez at gmail dot com>
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* Copyright (c) 2015, Redis Labs, Inc
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of Redis nor the names of its contributors may be used
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* to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/* SDS allocator selection.
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*
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* This file is used in order to change the SDS allocator at compile time.
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* Just define the following defines to what you want to use. Also add
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* the include of your alternate allocator if needed (not needed in order
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* to use the default libc allocator). */
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#ifndef __SDS_ALLOC_H__
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#define __SDS_ALLOC_H__
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#include "zmalloc.h"
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#define s_malloc zmalloc
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#define s_realloc zrealloc
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#define s_trymalloc ztrymalloc
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#define s_tryrealloc ztryrealloc
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#define s_free zfree
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#define s_malloc_usable zmalloc_usable
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#define s_realloc_usable zrealloc_usable
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#define s_trymalloc_usable ztrymalloc_usable
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#define s_tryrealloc_usable ztryrealloc_usable
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#define s_malloc_size zmalloc_size
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#endif
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