Commit34afbba

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Use mmap MAP_NOSYNC option to limit shared memory writes

mmap() is rarely used for shared memory, but when it is, this option isuseful, particularly on the BSDs.Patch by Sean Chittenden

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+10

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lines changed

+10

-2

lines changed

Lines changed: 2 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -368,7 +368,7 @@ dsm_impl_posix(dsm_op op, dsm_handle handle, Size request_size,`
`368`	`368`
`369`	`369`	`/* Map it. */`
`370`	`370`	`address=mmap(NULL,request_size,PROT_READ \|PROT_WRITE,`
`371`		`-MAP_SHARED \|MAP_HASSEMAPHORE,fd,0);`
	`371`	`+MAP_SHARED \|MAP_HASSEMAPHORE \|MAP_NOSYNC,fd,0);`
`372`	`372`	`if (address==MAP_FAILED)`
`373`	`373`	`{`
`374`	`374`	`intsave_errno;`
`@@ -960,7 +960,7 @@ dsm_impl_mmap(dsm_op op, dsm_handle handle, Size request_size,`
`960`	`960`
`961`	`961`	`/* Map it. */`
`962`	`962`	`address=mmap(NULL,request_size,PROT_READ \|PROT_WRITE,`
`963`		`-MAP_SHARED \|MAP_HASSEMAPHORE,fd,0);`
	`963`	`+MAP_SHARED \|MAP_HASSEMAPHORE \|MAP_NOSYNC,fd,0);`
`964`	`964`	`if (address==MAP_FAILED)`
`965`	`965`	`{`
`966`	`966`	`intsave_errno;`

Lines changed: 8 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -30,6 +30,14 @@`
`30`	`30`	`#defineMAP_HASSEMAPHORE0`
`31`	`31`	`#endif`
`32`	`32`
	`33`	`+/*`
	`34`	`+ * BSD-derived systems use the MAP_NOSYNC flag to prevent dirty mmap(2)`
	`35`	`+ * pages from being gratuitously flushed to disk.`
	`36`	`+ */`
	`37`	`+#ifndefMAP_NOSYNC`
	`38`	`+#defineMAP_NOSYNC0`
	`39`	`+#endif`
	`40`	`+`
`33`	`41`	`#definePG_MMAP_FLAGS(MAP_SHARED\|MAP_ANONYMOUS\|MAP_HASSEMAPHORE)`
`34`	`42`
`35`	`43`	`/* Some really old systems don't define MAP_FAILED. */`

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