58 lines
1.7 KiB
Diff
58 lines
1.7 KiB
Diff
From: John Eckersberg <jeckersb@redhat.com>
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Date: Fri, 11 Oct 2019 13:06:20 -0400
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Subject: [PATCH] erl_child_setup: reduce number of calls to close()
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On systems without closefrom(), such as Linux, iterating over all
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possible file descriptors and calling close() for each is inefficient.
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This is markedly so when the maximum number of file descriptors has
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been tuned to a large number.
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Instead, walk the open descriptors under /dev/fd and close only those
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which are open.
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diff --git a/erts/emulator/sys/unix/erl_child_setup.c b/erts/emulator/sys/unix/erl_child_setup.c
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index 129861ebd5..7ddd753136 100644
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--- a/erts/emulator/sys/unix/erl_child_setup.c
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+++ b/erts/emulator/sys/unix/erl_child_setup.c
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@@ -411,6 +411,7 @@ main(int argc, char *argv[])
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int uds_fd = 3, max_fd = 3;
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#ifndef HAVE_CLOSEFROM
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int i;
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+ DIR *dir;
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#endif
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struct sigaction sa;
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@@ -426,11 +427,29 @@ main(int argc, char *argv[])
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#if defined(HAVE_CLOSEFROM)
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closefrom(4);
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#else
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- for (i = 4; i < max_files; i++)
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+ dir = opendir("/dev/fd");
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+ if (dir == NULL) { /* /dev/fd not available */
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+ for (i = 4; i < max_files; i++)
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#if defined(__ANDROID__)
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- if (i != system_properties_fd())
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+ if (i != system_properties_fd())
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#endif
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- (void) close(i);
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+ (void) close(i);
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+ } else {
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+ /* Iterate over fds obtained from /dev/fd */
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+ struct dirent *entry;
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+ int dir_fd = dirfd(dir);
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+
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+ while ((entry = readdir(dir)) != NULL) {
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+ i = atoi(entry->d_name);
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+#if defined(__ANDROID__)
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+ if (i != system_properties_fd())
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+#endif
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+ if (i >= 4 && i != dir_fd)
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+ (void) close(i);
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+ }
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+
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+ closedir(dir);
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+ }
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#endif
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if (pipe(sigchld_pipe) < 0) {
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