Author: mjg
Date: Wed Aug 5 09:24:38 2020
New Revision: 363891
URL: https://svnweb.freebsd.org/changeset/base/363891
Log:
cache: reduce zone alignment to 8 bytes
It used to be sizeof of the given struct to accomodate for 32 bit mips
doing 64 bit loads, but the same can be achieved with requireing just
64 bit alignment.
While here reorder struct namecache so that most commonly used fields
are closer.
Modified:
head/sys/kern/vfs_cache.c
Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c Wed Aug 5 09:24:00 2020 (r363890)
+++ head/sys/kern/vfs_cache.c Wed Aug 5 09:24:38 2020 (r363891)
@@ -122,9 +122,9 @@ _Static_assert(sizeof(struct negstate) <= sizeof(struc
"the state must fit in a union with a pointer without growing it");
struct namecache {
- CK_LIST_ENTRY(namecache) nc_hash;/* hash chain */
LIST_ENTRY(namecache) nc_src; /* source vnode list */
TAILQ_ENTRY(namecache) nc_dst; /* destination vnode list */
+ CK_LIST_ENTRY(namecache) nc_hash;/* hash chain */
struct vnode *nc_dvp; /* vnode of parent of name */
union {
struct vnode *nu_vp; /* vnode the name refers to */
@@ -142,6 +142,8 @@ struct namecache {
* to be stored. The nc_dotdottime field is used when a cache entry is mapping
* both a non-dotdot directory name plus dotdot for the directory's
* parent.
+ *
+ * See below for alignment requirement.
*/
struct namecache_ts {
struct timespec nc_time; /* timespec provided by fs */
@@ -150,6 +152,14 @@ struct namecache_ts {
struct namecache nc_nc;
};
+/*
+ * At least mips n32 performs 64-bit accesses to timespec as found
+ * in namecache_ts and requires them to be aligned. Since others
+ * may be in the same spot suffer a little bit and enforce the
+ * alignment for everyone. Note this is a nop for 64-bit platforms.
+ */
+#define CACHE_ZONE_ALIGNMENT UMA_ALIGNOF(time_t)
+
#define nc_vp n_un.nu_vp
#define nc_neg n_un.nu_neg
@@ -2053,19 +2063,19 @@ nchinit(void *dummy __unused)
cache_zone_small = uma_zcreate("S VFS Cache",
sizeof(struct namecache) + CACHE_PATH_CUTOFF + 1,
- NULL, NULL, NULL, NULL, UMA_ALIGNOF(struct namecache),
+ NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT,
UMA_ZONE_ZINIT);
cache_zone_small_ts = uma_zcreate("STS VFS Cache",
sizeof(struct namecache_ts) + CACHE_PATH_CUTOFF + 1,
- NULL, NULL, NULL, NULL, UMA_ALIGNOF(struct namecache_ts),
+ NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT,
UMA_ZONE_ZINIT);
cache_zone_large = uma_zcreate("L VFS Cache",
sizeof(struct namecache) + NAME_MAX + 1,
- NULL, NULL, NULL, NULL, UMA_ALIGNOF(struct namecache),
+ NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT,
UMA_ZONE_ZINIT);
cache_zone_large_ts = uma_zcreate("LTS VFS Cache",
sizeof(struct namecache_ts) + NAME_MAX + 1,
- NULL, NULL, NULL, NULL, UMA_ALIGNOF(struct namecache_ts),
+ NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT,
UMA_ZONE_ZINIT);
VFS_SMR_ZONE_SET(cache_zone_small);
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