211 lines
6.0 KiB
C
211 lines
6.0 KiB
C
/* $NetBSD: rf_memchunk.c,v 1.5 2001/07/18 06:45:33 thorpej Exp $ */
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/*
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* Copyright (c) 1995 Carnegie-Mellon University.
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* All rights reserved.
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*
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* Author: Mark Holland
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*
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* Permission to use, copy, modify and distribute this software and
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* its documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
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* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*/
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/*********************************************************************************
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* rf_memchunk.c
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*
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* experimental code. I've found that the malloc and free calls in the DAG
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* creation code are very expensive. Since for any given workload the DAGs
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* created for different accesses are likely to be similar to each other, the
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* amount of memory used for any given DAG data structure is likely to be one
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* of a small number of values. For example, in UNIX, all reads and writes will
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* be less than 8k and will not span stripe unit boundaries. Thus in the absence
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* of failure, the only DAGs that will ever get created are single-node reads
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* and single-stripe-unit atomic read-modify-writes. So, I'm very likely to
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* be continually asking for chunks of memory equal to the sizes of these two
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* DAGs.
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*
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* This leads to the idea of holding on to these chunks of memory when the DAG is
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* freed and then, when a new DAG is created, trying to find such a chunk before
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* calling malloc.
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*
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* the "chunk list" is a list of lists. Each header node contains a size value
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* and a pointer to a list of chunk descriptors, each of which holds a pointer
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* to a chunk of memory of the indicated size.
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*
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* There is currently no way to purge memory out of the chunk list. My
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* initial thought on this is to have a low-priority thread that wakes up every
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* 1 or 2 seconds, purges all the chunks with low reuse counts, and sets all
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* the reuse counts to zero.
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*
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* This whole idea may be bad, since malloc may be able to do this more efficiently.
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* It's worth a try, though, and it can be turned off by setting useMemChunks to 0.
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*
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********************************************************************************/
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#include "rf_types.h"
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#include "rf_threadstuff.h"
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#include "rf_debugMem.h"
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#include "rf_memchunk.h"
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#include "rf_general.h"
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#include "rf_options.h"
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#include "rf_shutdown.h"
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typedef struct RF_ChunkHdr_s RF_ChunkHdr_t;
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struct RF_ChunkHdr_s {
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int size;
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RF_ChunkDesc_t *list;
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RF_ChunkHdr_t *next;
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};
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static RF_ChunkHdr_t *chunklist, *chunk_hdr_free_list;
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static RF_ChunkDesc_t *chunk_desc_free_list;
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RF_DECLARE_STATIC_MUTEX(chunkmutex)
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static void rf_ShutdownMemChunk(void *);
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static RF_ChunkDesc_t *NewMemChunk(int, char *);
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static void rf_ShutdownMemChunk(ignored)
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void *ignored;
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{
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RF_ChunkDesc_t *pt, *p;
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RF_ChunkHdr_t *hdr, *ht;
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if (rf_memChunkDebug)
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printf("Chunklist:\n");
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for (hdr = chunklist; hdr;) {
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for (p = hdr->list; p;) {
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if (rf_memChunkDebug)
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printf("Size %d reuse count %d\n", p->size, p->reuse_count);
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pt = p;
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p = p->next;
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RF_Free(pt->buf, pt->size);
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RF_Free(pt, sizeof(*pt));
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}
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ht = hdr;
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hdr = hdr->next;
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RF_Free(ht, sizeof(*ht));
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}
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rf_mutex_destroy(&chunkmutex);
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}
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int
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rf_ConfigureMemChunk(listp)
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RF_ShutdownList_t **listp;
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{
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int rc;
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chunklist = NULL;
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chunk_hdr_free_list = NULL;
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chunk_desc_free_list = NULL;
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rc = rf_mutex_init(&chunkmutex);
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if (rc) {
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RF_ERRORMSG3("Unable to init mutex file %s line %d rc=%d\n", __FILE__,
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__LINE__, rc);
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}
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rc = rf_ShutdownCreate(listp, rf_ShutdownMemChunk, NULL);
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if (rc) {
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RF_ERRORMSG3("Unable to add to shutdown list file %s line %d rc=%d\n", __FILE__,
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__LINE__, rc);
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rf_mutex_destroy(&chunkmutex);
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}
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return (rc);
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}
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/* called to get a chunk descriptor for a newly-allocated chunk of memory
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* MUTEX MUST BE LOCKED
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*
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* free list is not currently used
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*/
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static RF_ChunkDesc_t *
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NewMemChunk(size, buf)
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int size;
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char *buf;
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{
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RF_ChunkDesc_t *p;
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if (chunk_desc_free_list) {
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p = chunk_desc_free_list;
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chunk_desc_free_list = p->next;
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} else
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RF_Malloc(p, sizeof(RF_ChunkDesc_t), (RF_ChunkDesc_t *));
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p->size = size;
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p->buf = buf;
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p->next = NULL;
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p->reuse_count = 0;
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return (p);
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}
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/* looks for a chunk of memory of acceptable size. If none, allocates one and returns
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* a chunk descriptor for it, but does not install anything in the list. This is done
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* when the chunk is released.
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*/
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RF_ChunkDesc_t *
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rf_GetMemChunk(size)
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int size;
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{
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RF_ChunkHdr_t *hdr = chunklist;
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RF_ChunkDesc_t *p = NULL;
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char *buf;
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RF_LOCK_MUTEX(chunkmutex);
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for (hdr = chunklist; hdr; hdr = hdr->next)
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if (hdr->size >= size) {
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p = hdr->list;
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if (p) {
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hdr->list = p->next;
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p->next = NULL;
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p->reuse_count++;
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}
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break;
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}
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if (!p) {
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RF_Malloc(buf, size, (char *));
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p = NewMemChunk(size, buf);
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}
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RF_UNLOCK_MUTEX(chunkmutex);
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(void) memset(p->buf, 0, size);
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return (p);
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}
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void
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rf_ReleaseMemChunk(chunk)
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RF_ChunkDesc_t *chunk;
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{
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RF_ChunkHdr_t *hdr, *ht = NULL, *new;
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RF_LOCK_MUTEX(chunkmutex);
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for (hdr = chunklist; hdr && hdr->size < chunk->size; ht = hdr, hdr = hdr->next);
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if (hdr && hdr->size == chunk->size) {
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chunk->next = hdr->list;
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hdr->list = chunk;
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} else {
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RF_Malloc(new, sizeof(RF_ChunkHdr_t), (RF_ChunkHdr_t *));
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new->size = chunk->size;
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new->list = chunk;
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chunk->next = NULL;
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if (ht) {
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new->next = ht->next;
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ht->next = new;
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} else {
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new->next = hdr;
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chunklist = new;
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}
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}
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RF_UNLOCK_MUTEX(chunkmutex);
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}
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