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authorru <ru@FreeBSD.org>2002-03-15 18:04:00 +0000
committerru <ru@FreeBSD.org>2002-03-15 18:04:00 +0000
commitce2dae1bcd4d58c0d6a5feab6bf04d68290b406d (patch)
tree58f71e9811acef234e34698f3d19bbbeafd1a88d /lib/libc/sys
parentf77092ba102dd9276925ff17b4a7f9ebf145a28e (diff)
downloadFreeBSD-src-ce2dae1bcd4d58c0d6a5feab6bf04d68290b406d.zip
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mdoc(7) police: hard sentence breaks, whitespace at EOL, contractions.
Diffstat (limited to 'lib/libc/sys')
-rw-r--r--lib/libc/sys/mmap.228
1 files changed, 18 insertions, 10 deletions
diff --git a/lib/libc/sys/mmap.2 b/lib/libc/sys/mmap.2
index fa04607..dd3ef71 100644
--- a/lib/libc/sys/mmap.2
+++ b/lib/libc/sys/mmap.2
@@ -140,14 +140,17 @@ Causes data dirtied via this VM map to be flushed to physical media
only when necessary (usually by the pager) rather then gratuitously.
Typically this prevents the update daemons from flushing pages dirtied
through such maps and thus allows efficient sharing of memory across
-unassociated processes using a file-backed shared memory map. Without
+unassociated processes using a file-backed shared memory map.
+Without
this option any VM pages you dirty may be flushed to disk every so often
(every 30-60 seconds usually) which can create performance problems if you
do not need that to occur (such as when you are using shared file-backed
-mmap regions for IPC purposes). Note that VM/filesystem coherency is
+mmap regions for IPC purposes).
+Note that VM/filesystem coherency is
maintained whether you use
.Dv MAP_NOSYNC
-or not. This option is not portable
+or not.
+This option is not portable
across
.Ux
platforms (yet), though some may implement the same behavior
@@ -185,7 +188,8 @@ while reading a large file sequentially, e.g. using
The
.Xr fsync 2
function will flush all dirty data and metadata associated with a file,
-including dirty NOSYNC VM data, to physical media. The
+including dirty NOSYNC VM data, to physical media.
+The
.Xr sync 8
command and
.Xr sync 2
@@ -194,7 +198,8 @@ The
.Xr msync 2
system call is obsolete since
.Bx
-implements a coherent filesystem buffer cache. However, it may be
+implements a coherent filesystem buffer cache.
+However, it may be
used to associate dirty VM pages with filesystem buffers and thus cause
them to be flushed to physical media sooner rather then later.
.It Dv MAP_PRIVATE
@@ -218,10 +223,12 @@ and
This option creates
a memory region that grows to at most
.Fa len
-bytes in size, starting from the stack top and growing down. The
+bytes in size, starting from the stack top and growing down.
+The
stack top is the starting address returned by the call, plus
.Fa len
-bytes. The bottom of the stack at maximum growth is the starting
+bytes.
+The bottom of the stack at maximum growth is the starting
address returned by the call.
.El
.Pp
@@ -302,7 +309,7 @@ below.)
.Dv MAP_FIXED
was specified and the
.Fa addr
-parameter wasn't available.
+parameter was not available.
.Dv MAP_ANON
was specified and insufficient memory was available.
The system has reached the per-process mmap limit specified in the
@@ -322,7 +329,8 @@ sysctl.
.Xr make.conf 5
.Sh BUGS
.Fa len
-is limited to 2GB. Mmapping slightly more than 2GB doesn't work, but
+is limited to 2GB.
+Mmapping slightly more than 2GB does not work, but
it is possible to map a window of size (filesize % 2GB) for file sizes
of slightly less than 2G, 4GB, 6GB and 8GB.
.Pp
@@ -338,7 +346,7 @@ uses 32bit page indexes and
this gives
.Fx
a maximum of 8TB filesizes.
-It's actually bugs in
+It is actually bugs in
the filesystem code that causes the limit to be further restricted to
1TB (loss of precision when doing blockno calculations).
.Pp
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