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Marginal performance improvement in LockBuffer --- calculate address

of BufferLocks[] entry just once. Seems to save 10% or so of theroutine's runtime, which'd not be worth worrying about if it weren'tsuch a hotspot.

1 parente02cde4 commitc40a0a1Copy full SHA for c40a0a1

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+19

-17

lines changed

src/backend/storage/buffer
- bufmgr.c

1 file changed

+19

-17

lines changed

`‎src/backend/storage/buffer/bufmgr.c`

Lines changed: 19 additions & 17 deletions

Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@`
`8`	`8`	`*`
`9`	`9`	`*`
`10`	`10`	`* IDENTIFICATION`
`11`		`- * $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.75 2000/02/21 18:49:00 tgl Exp $`
	`11`	`+ * $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.76 2000/03/14 22:46:27 tgl Exp $`
`12`	`12`	`*`
`13`	`13`	`*-------------------------------------------------------------------------`
`14`	`14`	`*/`
`@@ -2072,12 +2072,14 @@ void`
`2072`	`2072`	`LockBuffer(Bufferbuffer,intmode)`
`2073`	`2073`	`{`
`2074`	`2074`	`BufferDesc*buf;`
	`2075`	`+bits8*buflock;`
`2075`	`2076`
`2076`	`2077`	`Assert(BufferIsValid(buffer));`
`2077`	`2078`	`if (BufferIsLocal(buffer))`
`2078`	`2079`	`return;`
`2079`	`2080`
`2080`	`2081`	`buf=&(BufferDescriptors[buffer-1]);`
	`2082`	`+buflock=&(BufferLocks[buffer-1]);`
`2081`	`2083`
`2082`	`2084`	`#ifdefHAS_TEST_AND_SET`
`2083`	`2085`	`S_LOCK(&(buf->cntx_lock));`
`@@ -2087,21 +2089,21 @@ LockBuffer(Buffer buffer, int mode)`
`2087`	`2089`
`2088`	`2090`	`if (mode==BUFFER_LOCK_UNLOCK)`
`2089`	`2091`	`{`
`2090`		`-if (BufferLocks[buffer-1]&BL_R_LOCK)`
	`2092`	`+if (*buflock&BL_R_LOCK)`
`2091`	`2093`	`{`
`2092`	`2094`	`Assert(buf->r_locks>0);`
`2093`	`2095`	`Assert(!(buf->w_lock));`
`2094`		`-Assert(!(BufferLocks[buffer-1]& (BL_W_LOCK \|BL_RI_LOCK)))`
`2095`		`-(buf->r_locks)--;`
`2096`		`-BufferLocks[buffer-1] &= ~BL_R_LOCK;`
	`2096`	`+Assert(!(*buflock& (BL_W_LOCK \|BL_RI_LOCK)));`
	`2097`	`+(buf->r_locks)--;`
	`2098`	`+*buflock &= ~BL_R_LOCK;`
`2097`	`2099`	`}`
`2098`		`-elseif (BufferLocks[buffer-1]&BL_W_LOCK)`
	`2100`	`+elseif (*buflock&BL_W_LOCK)`
`2099`	`2101`	`{`
`2100`	`2102`	`Assert(buf->w_lock);`
`2101`	`2103`	`Assert(buf->r_locks==0);`
`2102`		`-Assert(!(BufferLocks[buffer-1]& (BL_R_LOCK \|BL_RI_LOCK)))`
`2103`		`-buf->w_lock= false;`
`2104`		`-BufferLocks[buffer-1] &= ~BL_W_LOCK;`
	`2104`	`+Assert(!(*buflock& (BL_R_LOCK \|BL_RI_LOCK)));`
	`2105`	`+buf->w_lock= false;`
	`2106`	`+*buflock &= ~BL_W_LOCK;`
`2105`	`2107`	`}`
`2106`	`2108`	`else`
`2107`	`2109`	`elog(ERROR,"UNLockBuffer: buffer %lu is not locked",buffer);`
`@@ -2110,7 +2112,7 @@ LockBuffer(Buffer buffer, int mode)`
`2110`	`2112`	`{`
`2111`	`2113`	`unsignedi=0;`
`2112`	`2114`
`2113`		`-Assert(!(BufferLocks[buffer-1]& (BL_R_LOCK \|BL_W_LOCK \|BL_RI_LOCK)));`
	`2115`	`+Assert(!(*buflock& (BL_R_LOCK \|BL_W_LOCK \|BL_RI_LOCK)));`
`2114`	`2116`	`while (buf->ri_lock\|\|buf->w_lock)`
`2115`	`2117`	`{`
`2116`	`2118`	`#ifdefHAS_TEST_AND_SET`
`@@ -2124,24 +2126,24 @@ LockBuffer(Buffer buffer, int mode)`
`2124`	`2126`	`#endif`
`2125`	`2127`	`}`
`2126`	`2128`	`(buf->r_locks)++;`
`2127`		`-BufferLocks[buffer-1] \|=BL_R_LOCK;`
	`2129`	`+*buflock \|=BL_R_LOCK;`
`2128`	`2130`	`}`
`2129`	`2131`	`elseif (mode==BUFFER_LOCK_EXCLUSIVE)`
`2130`	`2132`	`{`
`2131`	`2133`	`unsignedi=0;`
`2132`	`2134`
`2133`		`-Assert(!(BufferLocks[buffer-1]& (BL_R_LOCK \|BL_W_LOCK \|BL_RI_LOCK)));`
	`2135`	`+Assert(!(*buflock& (BL_R_LOCK \|BL_W_LOCK \|BL_RI_LOCK)));`
`2134`	`2136`	`while (buf->r_locks>0\|\|buf->w_lock)`
`2135`	`2137`	`{`
`2136`		`-if (buf->r_locks>3\|\| (BufferLocks[buffer-1]&BL_RI_LOCK))`
	`2138`	`+if (buf->r_locks>3\|\| (*buflock&BL_RI_LOCK))`
`2137`	`2139`	`{`
`2138`	`2140`	`/*`
`2139`	`2141`	`* Our RI lock might be removed by concurrent W lock`
`2140`	`2142`	`* acquiring (see what we do with RI locks below`
`2141`	`2143`	`* when our own W acquiring succeeded) and so`
`2142`	`2144`	`* we set RI lock again if we already did this.`
`2143`	`2145`	`*/`
`2144`		`-BufferLocks[buffer-1] \|=BL_RI_LOCK;`
	`2146`	`+*buflock \|=BL_RI_LOCK;`
`2145`	`2147`	`buf->ri_lock= true;`
`2146`	`2148`	`}`
`2147`	`2149`	`#ifdefHAS_TEST_AND_SET`
`@@ -2155,15 +2157,15 @@ LockBuffer(Buffer buffer, int mode)`
`2155`	`2157`	`#endif`
`2156`	`2158`	`}`
`2157`	`2159`	`buf->w_lock= true;`
`2158`		`-BufferLocks[buffer-1] \|=BL_W_LOCK;`
`2159`		`-if (BufferLocks[buffer-1]&BL_RI_LOCK)`
	`2160`	`+*buflock \|=BL_W_LOCK;`
	`2161`	`+if (*buflock&BL_RI_LOCK)`
`2160`	`2162`	`{`
`2161`	`2163`	`/*`
`2162`	`2164`	`* It's possible to remove RI locks acquired by another`
`2163`	`2165`	`* W lockers here, but they'll take care about it.`
`2164`	`2166`	`*/`
`2165`	`2167`	`buf->ri_lock= false;`
`2166`		`-BufferLocks[buffer-1] &= ~BL_RI_LOCK;`
	`2168`	`+*buflock &= ~BL_RI_LOCK;`
`2167`	`2169`	`}`
`2168`	`2170`	`}`
`2169`	`2171`	`else`

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Commitc40a0a1

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`‎src/backend/storage/buffer/bufmgr.c`

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