pull: Add --per-object-fsync

This is the opposite of
https://github.com/ostreedev/ostree/issues/1184

Motivated by OpenShift seeing etcd performance issues during
OS updates: https://github.com/openshift/machine-config-operator/issues/1897

Basically, if we switch to invoking `fsync()` as we go, it makes
ostree performance worse (in my tests, 31s to write 2G versus 7s if we
delay sync) but it avoids *huge* outliers in `fsync()` time for etcd.

2 files changed, 10 insertions, 1 deletions

diff --git a/src/ostree/ot-builtin-pull-local.c b/src/ostree/ot-builtin-pull-local.c
index c42d38d7..43f4f255 100644
--- a/src/ostree/ot-builtin-pull-local.c
+++ b/src/ostree/ot-builtin-pull-local.c
@@ -34,6 +34,7 @@
 static char *opt_remote;
 static gboolean opt_commit_only;
 static gboolean opt_disable_fsync;
+static gboolean opt_per_object_fsync;
 static gboolean opt_untrusted;
 static gboolean opt_bareuseronly_files;
 static gboolean opt_require_static_deltas;
@@ -50,6 +51,7 @@ static GOptionEntry options[] = {
   { "commit-metadata-only", 0, 0, G_OPTION_ARG_NONE, &opt_commit_only, "Fetch only the commit metadata", NULL },
   { "remote", 0, 0, G_OPTION_ARG_STRING, &opt_remote, "Add REMOTE to refspec", "REMOTE" },
   { "disable-fsync", 0, 0, G_OPTION_ARG_NONE, &opt_disable_fsync, "Do not invoke fsync()", NULL },
+  { "per-object-fsync", 0, 0, G_OPTION_ARG_NONE, &opt_per_object_fsync, "Perform writes in such a way that avoids stalling concurrent processes", NULL },
   { "untrusted", 0, 0, G_OPTION_ARG_NONE, &opt_untrusted, "Verify checksums of local sources (always enabled for HTTP pulls)", NULL },
   { "bareuseronly-files", 0, 0, G_OPTION_ARG_NONE, &opt_bareuseronly_files, "Reject regular files with mode outside of 0775 (world writable, suid, etc.)", NULL },
   { "require-static-deltas", 0, 0, G_OPTION_ARG_NONE, &opt_require_static_deltas, "Require static deltas", NULL },
@@ -188,6 +190,9 @@ ostree_builtin_pull_local (int argc, char **argv, OstreeCommandInvocation *invoc
                            g_variant_new_variant (g_variant_new_boolean (TRUE)));
     g_variant_builder_add (&builder, "{s@v}", "disable-sign-verify-summary",
                            g_variant_new_variant (g_variant_new_boolean (TRUE)));
+    if (opt_per_object_fsync)
+        g_variant_builder_add (&builder, "{s@v}", "per-object-fsync",
+                           g_variant_new_variant (g_variant_new_boolean (TRUE)));
 
     if (console.is_tty)
       progress = ostree_async_progress_new_and_connect (ostree_repo_pull_default_console_progress_changed, &console);
diff --git a/src/ostree/ot-builtin-pull.c b/src/ostree/ot-builtin-pull.c
index 1625ab47..e69d62e3 100644
--- a/src/ostree/ot-builtin-pull.c
+++ b/src/ostree/ot-builtin-pull.c
@@ -29,6 +29,7 @@
 #include "otutil.h"
 
 static gboolean opt_disable_fsync;
+static gboolean opt_per_object_fsync;
 static gboolean opt_mirror;
 static gboolean opt_commit_only;
 static gboolean opt_dry_run;
@@ -58,6 +59,7 @@ static GOptionEntry options[] = {
    { "commit-metadata-only", 0, 0, G_OPTION_ARG_NONE, &opt_commit_only, "Fetch only the commit metadata", NULL },
    { "cache-dir", 0, 0, G_OPTION_ARG_FILENAME, &opt_cache_dir, "Use custom cache dir", NULL },
    { "disable-fsync", 0, 0, G_OPTION_ARG_NONE, &opt_disable_fsync, "Do not invoke fsync()", NULL },
+   { "per-object-fsync", 0, 0, G_OPTION_ARG_NONE, &opt_per_object_fsync, "Perform writes in such a way that avoids stalling concurrent processes", NULL },
    { "disable-static-deltas", 0, 0, G_OPTION_ARG_NONE, &opt_disable_static_deltas, "Do not use static deltas", NULL },
    { "require-static-deltas", 0, 0, G_OPTION_ARG_NONE, &opt_require_static_deltas, "Require static deltas", NULL },
    { "mirror", 0, 0, G_OPTION_ARG_NONE, &opt_mirror, "Write refs suitable for a mirror and fetches all refs if none provided", NULL },
@@ -325,7 +327,9 @@ ostree_builtin_pull (int argc, char **argv, OstreeCommandInvocation *invocation,
     if (opt_localcache_repos)
       g_variant_builder_add (&builder, "{s@v}", "localcache-repos",
                              g_variant_new_variant (g_variant_new_strv ((const char*const*)opt_localcache_repos, -1)));
-
+    if (opt_per_object_fsync)
+      g_variant_builder_add (&builder, "{s@v}", "per-object-fsync",
+                             g_variant_new_variant (g_variant_new_boolean (TRUE)));
     if (opt_http_headers)
       {
         GVariantBuilder hdr_builder;