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core: Use eventfd for alert pipes on Linux when possible

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The primary win of switching to eventfd when possible is that it only
uses a single file descriptor while pipe() will use two. This means for
each bridge channel we're reducing the number of required file
descriptors by 1, and - if you're using timerfd - we also now have 1
less file descriptor per Asterisk channel.

The API is not ideal (passing int arrays), but this is the cleanest
approach I could come up with to maintain API/ABI.

I've also removed what I believe to be an erroneous code block that
checked the non-blocking flag on the pipe ends for each read. If the
file descriptor is 'losing' its non-blocking mode, it is because of a
bug somewhere else in our code.

In my testing I haven't seen any measurable difference in performance.

Change-Id: Iff0fb1573e7f7a187d5211ddc60aa8f3da3edb1d
This commit is contained in:
Sean Bright
2017-04-17 20:06:10 -04:00
parent dc6654d969
commit 59203c51cc
9 changed files with 394 additions and 197 deletions
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35
configure vendored
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@@ -18009,6 +18009,41 @@ fi
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if we have usable eventfd support" >&5
$as_echo_n "checking if we have usable eventfd support... " >&6; }
if test "$cross_compiling" = yes; then :
{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
as_fn_error $? "cannot run test program while cross compiling
See \`config.log' for more details" "$LINENO" 5; }
else
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <sys/eventfd.h>
int
main ()
{
return eventfd(0, EFD_NONBLOCK | EFD_SEMAPHORE) == -1;
;
return 0;
}
_ACEOF
if ac_fn_c_try_run "$LINENO"; then :
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
$as_echo "yes" >&6; }
$as_echo "#define HAVE_EVENTFD 1" >>confdefs.h
else
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
$as_echo "no" >&6; }
fi
rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
conftest.$ac_objext conftest.beam conftest.$ac_ext
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for compiler 'attribute pure' support" >&5
$as_echo_n "checking for compiler 'attribute pure' support... " >&6; }