Comments about GetFreeXLBuffer().

GetFreeXLBuffer(): use Insert->LgwrResult instead of private LgwrResult
copy if it's more fresh (attempt to avoid acquiring info_lck/lgwr_lck).

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8b701a85dfcc185039750420cd983aabcb7363c5..7c18f0ff5a69564c0b6b12d16d875f4086b88abf 100644 (file)
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.52 2001/02/13 08:44:09 vadim Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.53 2001/02/13 20:40:25 vadim Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -612,6 +612,7 @@ begin:;
    if (updrqst)
    {
        S_LOCK(&(XLogCtl->info_lck));
+       LgwrResult = XLogCtl->LgwrResult;
        if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrRqst.Write))
            XLogCtl->LgwrRqst.Write = LgwrRqst.Write;
        S_UNLOCK(&(XLogCtl->info_lck));
@@ -760,6 +761,10 @@ XLogFlush(XLogRecPtr record)
 
 }
 
+/*
+ * We use this routine when Insert->curridx block is full and the next XLOG
+ * buffer looks as unwritten to OS' cache. insert_lck is assumed here.
+ */
 static void
 GetFreeXLBuffer()
 {
@@ -768,12 +773,24 @@ GetFreeXLBuffer()
    uint16      curridx = NextBufIdx(Insert->curridx);
    unsigned    spins = 0;
 
+   /* Use Insert->LgwrResult copy if it's more fresh */
+   if (XLByteLT(LgwrResult.Write, Insert->LgwrResult.Write))
+   {
+       LgwrResult = Insert->LgwrResult;
+       if (XLByteLE(XLogCtl->xlblocks[curridx], LgwrResult.Write))
+       {
+           InitXLBuffer(curridx);
+           return;
+       }
+   }
+
    LgwrRqst.Write = XLogCtl->xlblocks[Insert->curridx];
    for (;;)
    {
        if (!TAS(&(XLogCtl->info_lck)))
        {
            LgwrResult = XLogCtl->LgwrResult;
+           /* LgwrRqst.Write GE XLogCtl->LgwrRqst.Write */
            XLogCtl->LgwrRqst.Write = LgwrRqst.Write;
            S_UNLOCK(&(XLogCtl->info_lck));
            if (XLByteLE(XLogCtl->xlblocks[curridx], LgwrResult.Write))