Date: Fri, 23 Oct 2020 15:56:22 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r366976 - head/sys/kern Message-ID: <202010231556.09NFuMFb079616@repo.freebsd.org>
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Author: mjg Date: Fri Oct 23 15:56:22 2020 New Revision: 366976 URL: https://svnweb.freebsd.org/changeset/base/366976 Log: cache: reduce memory waste in struct namecache The previous scheme for calculating the total size was doing sizeof on the struct and then adding the wanted space for the buffer. nc_name is at offset 58 while sizeof(struct namecache) is 64. With CACHE_PATH_CUTOFF of 39 bytes and 1 byte of padding we were allocating 104 bytes for the entry and never accounting for the 6 byte padding, wasting that space. Modified: head/sys/kern/vfs_cache.c Modified: head/sys/kern/vfs_cache.c ============================================================================== --- head/sys/kern/vfs_cache.c Fri Oct 23 15:50:49 2020 (r366975) +++ head/sys/kern/vfs_cache.c Fri Oct 23 15:56:22 2020 (r366976) @@ -162,6 +162,7 @@ struct namecache_ts { struct timespec nc_time; /* timespec provided by fs */ struct timespec nc_dotdottime; /* dotdot timespec provided by fs */ int nc_ticks; /* ticks value when entry was added */ + int nc_pad; struct namecache nc_nc; }; @@ -172,12 +173,19 @@ struct namecache_ts { * alignment for everyone. Note this is a nop for 64-bit platforms. */ #define CACHE_ZONE_ALIGNMENT UMA_ALIGNOF(time_t) -#define CACHE_PATH_CUTOFF 39 -#define CACHE_ZONE_SMALL_SIZE (sizeof(struct namecache) + CACHE_PATH_CUTOFF + 1) -#define CACHE_ZONE_SMALL_TS_SIZE (sizeof(struct namecache_ts) + CACHE_PATH_CUTOFF + 1) -#define CACHE_ZONE_LARGE_SIZE (sizeof(struct namecache) + NAME_MAX + 1) -#define CACHE_ZONE_LARGE_TS_SIZE (sizeof(struct namecache_ts) + NAME_MAX + 1) +#ifdef __LP64__ +#define CACHE_PATH_CUTOFF 45 +#define CACHE_LARGE_PAD 6 +#else +#define CACHE_PATH_CUTOFF 41 +#define CACHE_LARGE_PAD 2 +#endif + +#define CACHE_ZONE_SMALL_SIZE (offsetof(struct namecache, nc_name) + CACHE_PATH_CUTOFF + 1) +#define CACHE_ZONE_SMALL_TS_SIZE (offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_SMALL_SIZE) +#define CACHE_ZONE_LARGE_SIZE (offsetof(struct namecache, nc_name) + NAME_MAX + 1 + CACHE_LARGE_PAD) +#define CACHE_ZONE_LARGE_TS_SIZE (offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_LARGE_SIZE) _Static_assert((CACHE_ZONE_SMALL_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size"); _Static_assert((CACHE_ZONE_SMALL_TS_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
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