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src: use closefrom() for mass closing of FDs

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On FreeBSD 12 the default ulimit settings allow for 100,000
open file descriptors. As a result spawning processes in
libvirt is abominably slow. Fortunately FreeBSD has long
since provided a good solution in the form of closefrom(),
which closes all FDs equal to or larger than the specified
parameter.

Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Your Name 2020-02-12 10:53:59 +00:00 committed by Daniel P. Berrangé
parent 800aed4644
commit 59afd9764d
1 changed files with 58 additions and 3 deletions
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61
src/util/vircommand.c
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@ -494,6 +494,60 @@ virCommandMassCloseGetFDsGeneric(virCommandPtr cmd G_GNUC_UNUSED,
}
# endif /* !__linux__ */
# ifdef __FreeBSD__
static int
virCommandMassClose(virCommandPtr cmd,
int childin,
int childout,
int childerr)
{
int lastfd = -1;
int fd = -1;
size_t i;
/*
* Two phases of closing.
*
* The first (inefficient) phase iterates over FDs,
* preserving certain FDs we need to pass down, and
* closing others. The number of iterations is bounded
* to the number of the biggest FD we need to preserve.
*
* The second (speedy) phase uses closefrom() to cull
* all remaining FDs in the process.
*
* Usually the first phase will be fairly quick only
* processing a handful of low FD numbers, and thus using
* closefrom() is a massive win for high ulimit() NFILES
* values.
*/
lastfd = MAX(lastfd, childin);
lastfd = MAX(lastfd, childout);
lastfd = MAX(lastfd, childerr);
for (i = 0; i < cmd->npassfd; i++)
lastfd = MAX(lastfd, cmd->passfd[i].fd);
for (fd = 0; fd <= lastfd; fd++) {
if (fd == childin || fd == childout || fd == childerr)
continue;
if (!virCommandFDIsSet(cmd, fd)) {
int tmpfd = fd;
VIR_MASS_CLOSE(tmpfd);
} else if (virSetInherit(fd, true) < 0) {
virReportSystemError(errno, _("failed to preserve fd %d"), fd);
return -1;
}
}
closefrom(lastfd + 1);
return 0;
}
# else /* ! __FreeBSD__ */
static int
virCommandMassClose(virCommandPtr cmd,
int childin,
@ -520,13 +574,13 @@ virCommandMassClose(virCommandPtr cmd,
if (!(fds = virBitmapNew(openmax)))
return -1;
# ifdef __linux__
# ifdef __linux__
if (virCommandMassCloseGetFDsLinux(cmd, fds) < 0)
return -1;
# else
# else
if (virCommandMassCloseGetFDsGeneric(cmd, fds) < 0)
return -1;
# endif
# endif
fd = virBitmapNextSetBit(fds, 2);
for (; fd >= 0; fd = virBitmapNextSetBit(fds, fd)) {
@ -544,6 +598,7 @@ virCommandMassClose(virCommandPtr cmd,
return 0;
}
# endif /* ! __FreeBSD__ */
/*
* virExec: