diff options
| author | Tomas Vondra | 2017-10-14 10:38:06 +0000 |
|---|---|---|
| committer | Tomas Vondra | 2017-10-14 10:52:04 +0000 |
| commit | 1078b079d5476e3447bd5268b317eacb4c455f5d (patch) | |
| tree | 9efbd40a8be0b13e769e2fe54885828bcaed3cd3 | |
| parent | 1c7637f35f5f8b4566c4483f02041e7fc89a83cc (diff) | |
Allocate thread-local snapshot array statically
Since commit fb56418d66 the snapshots are computed in thread-local
storage, but we haven't been freeing the memory (on thread exit).
As the memory is allocated in the global (TopMostMemoryContext),
this presented a memory leak of 64kB on each GTM connection.
One way to fix this would be to track when the thread-local storage
is used in GTM_GetTransactionSnapshot(), and allocate the memory
in TopMemoryContext (which is per-thread and released on exit).
But there's a simpler way - allocate the thread-specific storage as
part of GTM_ThreadInfo, and just redirect sn_xip from the snapshot.
This way we don't have to worry about palloc/pfree at all, and we
mostly assume that every connection will need to compute at least
one snapshot anyway.
Reported by Rob Canavan <[email protected]>, investigation and fix
by me. For more discussion see
<CAFTg0q6VC_11+c=Q=gsAcDsBrDjvuGKjzNwH4Lr8vERRDn4Ycw@mail.gmail.com>
Backpatch to Postgres-XL 9.5.
| -rw-r--r-- | src/gtm/main/gtm_snap.c | 4 | ||||
| -rw-r--r-- | src/gtm/main/gtm_thread.c | 5 | ||||
| -rw-r--r-- | src/include/gtm/gtm.h | 7 |
3 files changed, 16 insertions, 0 deletions
diff --git a/src/gtm/main/gtm_snap.c b/src/gtm/main/gtm_snap.c index 5a538985df..f8e3d31976 100644 --- a/src/gtm/main/gtm_snap.c +++ b/src/gtm/main/gtm_snap.c @@ -103,6 +103,10 @@ GTM_GetTransactionSnapshot(GTM_TransactionHandle handle[], int txn_count, int *s Assert(snapshot != NULL); + /* + * This can only happen when using a snapshot from GTMTransactions, as the + * thread-specific sn_xip array is allocated statically as part of GTM_ThreadInfo. + */ if (snapshot->sn_xip == NULL) { /* diff --git a/src/gtm/main/gtm_thread.c b/src/gtm/main/gtm_thread.c index c513f6a71f..9d166f4a0e 100644 --- a/src/gtm/main/gtm_thread.c +++ b/src/gtm/main/gtm_thread.c @@ -256,6 +256,11 @@ GTM_ThreadCreate(GTM_ConnectionInfo *conninfo, 8 * 1024, false); + /* + * Set the sn_xip pointer to the statically-allocated array (see GTM_ThreadInfo). + */ + thrinfo->thr_snapshot.sn_xip = thrinfo->thr_xip; + thrinfo->thr_startroutine = startroutine; /* diff --git a/src/include/gtm/gtm.h b/src/include/gtm/gtm.h index 37d31f6ba4..7b494fb6a2 100644 --- a/src/include/gtm/gtm.h +++ b/src/include/gtm/gtm.h @@ -59,6 +59,13 @@ typedef struct GTM_ThreadInfo GTM_RWLock thr_lock; gtm_List *thr_cached_txninfo; GTM_SnapshotData thr_snapshot; + + /* + * Statically allocated XID array for the snapshot. Every thread will need + * a snapshot anyway, and this way we don't have to worry about allocation + * and freeing of the memory at thread exit. + */ + GlobalTransactionId thr_xip[GTM_MAX_GLOBAL_TRANSACTIONS]; } GTM_ThreadInfo; typedef struct GTM_Threads |