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2864f11d34
* libguile/cache-internal.h (SCM_CACHE_SIZE): Bump to 16. It seems that a thread accesses more than 8 fluids by default (%stacks, the exception handler, current ports, current-fiber, port read/write waiters) which leads every fiber to cause cache eviction and copying the value table, which is a bottleneck. Instead just bump this cache size. (scm_cache_lookup): Update unrolled search.
112 lines
3 KiB
C
112 lines
3 KiB
C
#ifndef SCM_CACHE_INTERNAL_H
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#define SCM_CACHE_INTERNAL_H
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/* Copyright (C) 2016
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* Free Software Foundation, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public License
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* as published by the Free Software Foundation; either version 3 of
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* the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301 USA
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*/
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#include <string.h>
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#include "libguile/__scm.h"
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#include "libguile/gc.h"
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#include "libguile/hash.h"
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#include "libguile/threads.h"
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/* A simple cache with 8 entries. The cache entries are stored in a
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sorted vector. */
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struct scm_cache_entry
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{
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scm_t_bits key;
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scm_t_bits value;
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};
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#define SCM_CACHE_SIZE 16
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struct scm_cache
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{
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scm_t_bits eviction_cookie;
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struct scm_cache_entry entries[SCM_CACHE_SIZE];
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};
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static inline struct scm_cache*
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scm_make_cache (void)
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{
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struct scm_cache *ret = scm_gc_typed_calloc (struct scm_cache);
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ret->eviction_cookie = (scm_t_bits) ret;
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return ret;
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}
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static inline int
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scm_cache_full_p (struct scm_cache *cache)
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{
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return cache->entries[0].key != 0;
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}
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static inline void
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scm_cache_evict_1 (struct scm_cache *cache, struct scm_cache_entry *evicted)
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{
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size_t idx;
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cache->eviction_cookie = scm_ihashq (SCM_PACK (cache->eviction_cookie), -1);
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idx = cache->eviction_cookie & (SCM_CACHE_SIZE - 1);
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memcpy (evicted, cache->entries + idx, sizeof (*evicted));
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memmove (cache->entries + 1,
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cache->entries,
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sizeof (cache->entries[0]) * idx);
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cache->entries[0].key = 0;
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cache->entries[0].value = 0;
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}
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static inline struct scm_cache_entry*
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scm_cache_lookup (struct scm_cache *cache, SCM k)
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{
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scm_t_bits k_bits = SCM_UNPACK (k);
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struct scm_cache_entry *entry = cache->entries;
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/* Unrolled binary search, compiled to branchless cmp + cmov chain. */
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if (entry[8].key <= k_bits) entry += 8;
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if (entry[4].key <= k_bits) entry += 4;
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if (entry[2].key <= k_bits) entry += 2;
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if (entry[1].key <= k_bits) entry += 1;
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return entry;
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}
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static inline void
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scm_cache_insert (struct scm_cache *cache, SCM k, SCM v,
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struct scm_cache_entry *evicted)
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{
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struct scm_cache_entry *entry;
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if (scm_cache_full_p (cache))
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scm_cache_evict_1 (cache, evicted);
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entry = scm_cache_lookup (cache, k);
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if (entry->key == SCM_UNPACK (k))
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{
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entry->value = SCM_UNPACK (v);
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return;
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}
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memmove (cache->entries,
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cache->entries + 1,
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(entry - cache->entries) * sizeof (*entry));
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entry->key = SCM_UNPACK (k);
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entry->value = SCM_UNPACK (v);
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}
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#endif /* SCM_CACHE_INTERNAL_H */
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