From 9d6e4a916367e85ffdf37b1cb7b5cdb7ac0e15b5 Mon Sep 17 00:00:00 2001
From: Hallvard Furuseth <hallvard@openldap.org>
Date: Thu, 7 Nov 2013 23:38:15 +0100
Subject: [PATCH] ITS#7713 Handle bigger OS page sizes
Use DB page size = min(32k, OS pagesize). Previous limit was 8k
(MDB_MINKEYS*MDB_PAGESIZE).
Handle DB pagesize < OS pagesize. That's an I/O pessimization,
but transactions remain atomic: Only writing the MDB_meta must
be atomic, and it fits in one OS page.
Don't truncate desired subpage size: Asssign it to a size_t
(mv_size), not an uint16_t (mp_upper).
---
libraries/liblmdb/mdb.c | 70 ++++++++++++++++++++++++++---------------
1 file changed, 45 insertions(+), 25 deletions(-)
diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index a0ece4470d..19d5f20a5d 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -324,10 +324,13 @@ static txnid_t mdb_debug_start;
(((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
/** @} */
- /** A default memory page size.
- * The actual size is platform-dependent, but we use this for
- * boot-strapping. We probably should not be using this any more.
- * The #GET_PAGESIZE() macro is used to get the actual size.
+ /** @brief The maximum size of a database page.
+ *
+ * This is 32k, since it must fit in #MDB_page.#mp_upper.
+ *
+ * LMDB will use database pages < OS pages if needed.
+ * That causes more I/O in write transactions: The OS must
+ * know (read) the whole page before writing a partial page.
*
* Note that we don't currently support Huge pages. On Linux,
* regular data files cannot use Huge pages, and in general
@@ -336,7 +339,7 @@ static txnid_t mdb_debug_start;
* pressure from other processes is high. So until OSs have
* actual paging support for Huge pages, they're not viable.
*/
-#define MDB_PAGESIZE 4096
+#define MAX_PAGESIZE 0x8000
/** The minimum number of keys required in a database page.
* Setting this to a larger value will place a smaller bound on the
@@ -370,7 +373,7 @@ static txnid_t mdb_debug_start;
*
* We require that keys all fit onto a regular page. This limit
* could be raised a bit further if needed; to something just
- * under #MDB_PAGESIZE / #MDB_MINKEYS.
+ * under (page size / #MDB_MINKEYS).
*
* Note that data items in an #MDB_DUPSORT database are actually keys
* of a subDB, so they're also limited to this size.
@@ -813,19 +816,18 @@ typedef struct MDB_meta {
txnid_t mm_txnid; /**< txnid that committed this page */
} MDB_meta;
- /** Buffer for a stack-allocated dirty page.
+ /** Buffer for a stack-allocated meta page.
* The members define size and alignment, and silence type
* aliasing warnings. They are not used directly; that could
* mean incorrectly using several union members in parallel.
*/
-typedef union MDB_pagebuf {
- char mb_raw[MDB_PAGESIZE];
+typedef union MDB_metabuf {
MDB_page mb_page;
struct {
char mm_pad[PAGEHDRSZ];
MDB_meta mm_meta;
} mb_metabuf;
-} MDB_pagebuf;
+} MDB_metabuf;
/** Auxiliary DB info.
* The information here is mostly static/read-only. There is
@@ -994,7 +996,8 @@ struct MDB_env {
/** Have liveness lock in reader table */
#define MDB_LIVE_READER 0x08000000U
uint32_t me_flags; /**< @ref mdb_env */
- unsigned int me_psize; /**< size of a page, from #GET_PAGESIZE */
+ unsigned int me_psize; /**< DB page size, inited from me_os_psize */
+ unsigned int me_os_psize; /**< OS page size, from #GET_PAGESIZE */
unsigned int me_maxreaders; /**< size of the reader table */
unsigned int me_numreaders; /**< max numreaders set by this env */
MDB_dbi me_numdbs; /**< number of DBs opened */
@@ -1004,6 +1007,7 @@ struct MDB_env {
char *me_map; /**< the memory map of the data file */
MDB_txninfo *me_txns; /**< the memory map of the lock file or NULL */
MDB_meta *me_metas[2]; /**< pointers to the two meta pages */
+ void *me_pbuf; /**< scratch area for DUPSORT put() */
MDB_txn *me_txn; /**< current write transaction */
size_t me_mapsize; /**< size of the data memory map */
off_t me_size; /**< current file size */
@@ -2970,10 +2974,11 @@ fail:
static int
mdb_env_read_header(MDB_env *env, MDB_meta *meta)
{
- MDB_pagebuf pbuf;
+ MDB_metabuf pbuf;
MDB_page *p;
MDB_meta *m;
int i, rc, off;
+ enum { Size = sizeof(pbuf) };
/* We don't know the page size yet, so use a minimum value.
* Read both meta pages so we can use the latest one.
@@ -2985,13 +2990,13 @@ mdb_env_read_header(MDB_env *env, MDB_meta *meta)
OVERLAPPED ov;
memset(&ov, 0, sizeof(ov));
ov.Offset = off;
- rc = ReadFile(env->me_fd,&pbuf,MDB_PAGESIZE,&len,&ov) ? (int)len : -1;
+ rc = ReadFile(env->me_fd, &pbuf, Size, &len, &ov) ? (int)len : -1;
if (rc == -1 && ErrCode() == ERROR_HANDLE_EOF)
rc = 0;
#else
- rc = pread(env->me_fd, &pbuf, MDB_PAGESIZE, off);
+ rc = pread(env->me_fd, &pbuf, Size, off);
#endif
- if (rc != MDB_PAGESIZE) {
+ if (rc != Size) {
if (rc == 0 && off == 0)
return ENOENT;
rc = rc < 0 ? (int) ErrCode() : MDB_INVALID;
@@ -3122,11 +3127,18 @@ mdb_env_write_meta(MDB_txn *txn)
mp->mm_last_pg = txn->mt_next_pgno - 1;
mp->mm_txnid = txn->mt_txnid;
if (!(env->me_flags & (MDB_NOMETASYNC|MDB_NOSYNC))) {
+ unsigned meta_size = env->me_psize;
rc = (env->me_flags & MDB_MAPASYNC) ? MS_ASYNC : MS_SYNC;
ptr = env->me_map;
- if (toggle)
- ptr += env->me_psize;
- if (MDB_MSYNC(ptr, env->me_psize, rc)) {
+ if (toggle) {
+#ifndef _WIN32 /* POSIX msync() requires ptr = start of OS page */
+ if (meta_size < env->me_os_psize)
+ meta_size += meta_size;
+ else
+#endif
+ ptr += meta_size;
+ }
+ if (MDB_MSYNC(ptr, meta_size, rc)) {
rc = ErrCode();
goto fail;
}
@@ -3232,6 +3244,7 @@ mdb_env_create(MDB_env **env)
e->me_wmutex = SEM_FAILED;
#endif
e->me_pid = getpid();
+ GET_PAGESIZE(e->me_os_psize);
VGMEMP_CREATE(e,0,0);
*env = e;
return MDB_SUCCESS;
@@ -3397,7 +3410,9 @@ mdb_env_open2(MDB_env *env)
return i;
DPUTS("new mdbenv");
newenv = 1;
- GET_PAGESIZE(env->me_psize);
+ env->me_psize = env->me_os_psize;
+ if (env->me_psize > MAX_PAGESIZE)
+ env->me_psize = MAX_PAGESIZE;
} else {
env->me_psize = meta.mm_psize;
}
@@ -4042,7 +4057,12 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode
DPRINTF(("opened dbenv %p", (void *) env));
if (excl > 0) {
rc = mdb_env_share_locks(env, &excl);
+ if (rc)
+ goto leave;
}
+ if (!((flags & MDB_RDONLY) ||
+ (env->me_pbuf = calloc(1, env->me_psize))))
+ rc = ENOMEM;
}
leave:
@@ -4066,6 +4086,7 @@ mdb_env_close0(MDB_env *env, int excl)
for (i = env->me_maxdbs; --i > MAIN_DBI; )
free(env->me_dbxs[i].md_name.mv_data);
+ free(env->me_pbuf);
free(env->me_dbflags);
free(env->me_dbxs);
free(env->me_path);
@@ -5611,7 +5632,6 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
unsigned int mcount = 0, dcount = 0, nospill;
size_t nsize;
int rc, rc2;
- MDB_pagebuf pbuf;
char dbuf[MDB_MAXKEYSIZE+1];
unsigned int nflags;
DKBUF;
@@ -5747,7 +5767,7 @@ more:
/* DB has dups? */
if (F_ISSET(mc->mc_db->md_flags, MDB_DUPSORT)) {
- mp = fp = xdata.mv_data = &pbuf;
+ mp = fp = xdata.mv_data = env->me_pbuf;
mp->mp_pgno = mc->mc_pg[mc->mc_top]->mp_pgno;
/* Was a single item before, must convert now */
@@ -5781,16 +5801,16 @@ more:
dkey.mv_data = dbuf;
fp->mp_flags = P_LEAF|P_DIRTY|P_SUBP;
fp->mp_lower = PAGEHDRSZ;
- fp->mp_upper = PAGEHDRSZ + dkey.mv_size + data->mv_size;
+ xdata.mv_size = PAGEHDRSZ + dkey.mv_size + data->mv_size;
if (mc->mc_db->md_flags & MDB_DUPFIXED) {
fp->mp_flags |= P_LEAF2;
fp->mp_pad = data->mv_size;
- fp->mp_upper += 2 * data->mv_size; /* leave space for 2 more */
+ xdata.mv_size += 2 * data->mv_size; /* leave space for 2 more */
} else {
- fp->mp_upper += 2 * sizeof(indx_t) + 2 * NODESIZE +
+ xdata.mv_size += 2 * (sizeof(indx_t) + NODESIZE) +
(dkey.mv_size & 1) + (data->mv_size & 1);
}
- xdata.mv_size = fp->mp_upper;
+ fp->mp_upper = xdata.mv_size;
} else if (leaf->mn_flags & F_SUBDATA) {
/* Data is on sub-DB, just store it */
flags |= F_DUPDATA|F_SUBDATA;
--
GitLab