mount/fuse: expose auto-invalidation as a mount option

Auto invalidation is necessary when same (meta)data is shared/access
across multiple mounts. However, if (meta)data is not shared, all
relevant I/O goes through the cache of single mount and hence is
coherent with (meta)data on bricks always. So, fuse-auto-invalidation
can be disabled for this case which gives a huge performance boost for
workloads that write data and then immediately read the data they just
wrote.

From glusterfs --help,

<snip>
      --auto-invalidation[=BOOL]   controls whether fuse-kernel can
                             auto-invalidate attribute, dentry and page-cache.
                             Disable this only if same files/directories are
                             not accessed across two different mounts
                             concurrently [default: "on"]
</snip>

Details on how disabling auto-invalidation helped to reduce pgbench
init times can be found at [1]. Time taken for pgbench init of scale
8000 was 8340s. That will be an improvement of 86% (59280s vs 8340s)
with auto-invalidations turned off along with other
optimizations. Just disabling auto-invalidation contributed 56%
improvement by reducing the total time taken by 33260s.

[1] https://www.spinics.net/lists/gluster-devel/msg25907.html

Change-Id: I0ed730dba9064bd9c576ad1800170a21e100e1ce
Signed-off-by: Raghavendra Gowdappa <rgowdapp@redhat.com>
updates: bz#1664934

2 files changed, 25 insertions, 0 deletions

diff --git a/glusterfsd/src/glusterfsd.c b/glusterfsd/src/glusterfsd.c
index df5b9ed0b31..c1b66ef0d32 100644
--- a/glusterfsd/src/glusterfsd.c
+++ b/glusterfsd/src/glusterfsd.c
@@ -270,6 +270,11 @@ static struct argp_option gf_options[] = {
     {"fuse-flush-handle-interrupt", ARGP_FUSE_FLUSH_HANDLE_INTERRUPT_KEY,
      "BOOL", OPTION_ARG_OPTIONAL | OPTION_HIDDEN,
      "handle interrupt in fuse FLUSH handler"},
+    {"auto-invalidation", ARGP_FUSE_AUTO_INVAL_KEY, "BOOL", OPTION_ARG_OPTIONAL,
+     "controls whether fuse-kernel can auto-invalidate "
+     "attribute, dentry and page-cache. "
+     "Disable this only if same files/directories are not accessed across "
+     "two different mounts concurrently [default: \"on\"]"},
     {0, 0, 0, 0, "Miscellaneous Options:"},
     {
         0,
@@ -623,6 +628,15 @@ set_fuse_mount_options(glusterfs_ctx_t *ctx, dict_t *options)
             goto err;
         }
     }
+
+    ret = dict_set_uint32(options, "auto-invalidation",
+                          cmd_args->fuse_auto_inval);
+    if (ret < 0) {
+        gf_msg("glusterfsd", GF_LOG_ERROR, 0, glusterfsd_msg_4,
+               "failed to set dict value for key auto-invalidation");
+        goto err;
+    }
+
     switch (cmd_args->kernel_writeback_cache) {
         case GF_OPTION_ENABLE:
             ret = dict_set_static_ptr(options, "kernel-writeback-cache", "on");
@@ -1483,6 +1497,16 @@ parse_opts(int key, char *arg, struct argp_state *state)
                          "unknown fuse flush handle interrupt setting \"%s\"",
                          arg);
             break;
+        case ARGP_FUSE_AUTO_INVAL_KEY:
+            if (!arg)
+                arg = "yes";
+
+            if (gf_string2boolean(arg, &b) == 0) {
+                cmd_args->fuse_auto_inval = b;
+                break;
+            }
+
+            break;
     }
     return 0;
 }
diff --git a/glusterfsd/src/glusterfsd.h b/glusterfsd/src/glusterfsd.h
index 86ac61c1a92..35cf6d88b7a 100644
--- a/glusterfsd/src/glusterfsd.h
+++ b/glusterfsd/src/glusterfsd.h
@@ -110,6 +110,7 @@ enum argp_option_keys {
     ARGP_PRINT_LIBEXECDIR_KEY = 188,
     ARGP_FUSE_FLUSH_HANDLE_INTERRUPT_KEY = 189,
     ARGP_FUSE_LRU_LIMIT_KEY = 190,
+    ARGP_FUSE_AUTO_INVAL_KEY = 191,
 };
 
 struct _gfd_vol_top_priv {