OPTIM: vars: remove internal bookkeeping for vars_global_size
Right now we have a per-process max variable size and a per-scope one,
with the proc scope covering all others. As such, the per-process global
one is always exactly equal to the per-proc-scope one. And bookkeeping
on these process-wide variables is extremely expensive (up to 38% CPU
seen in var_accounting_diff() just for them).
Let's kill vars_global_size and only rely on the proc one. Doing this
increased the request rate from 770k to 1.06M in a config having only
12 variables on a 16-thread machine.
diff --git a/src/vars.c b/src/vars.c
index 0eaa4c9..c658f5a 100644
--- a/src/vars.c
+++ b/src/vars.c
@@ -28,7 +28,6 @@
/* This array of int contains the system limits per context. */
static unsigned int var_global_limit = 0;
-static unsigned int var_global_size = 0;
static unsigned int var_proc_limit = 0;
static unsigned int var_sess_limit = 0;
static unsigned int var_txn_limit = 0;
@@ -88,7 +87,6 @@
/* fall through */
case SCOPE_PROC:
_HA_ATOMIC_ADD(&proc_vars.size, size);
- _HA_ATOMIC_ADD(&var_global_size, size);
}
}
@@ -124,9 +122,12 @@
return 0;
/* fall through */
case SCOPE_PROC:
+ /* note: scope proc collects all others and is currently identical to the
+ * global limit.
+ */
if (var_proc_limit && proc_vars.size + size > var_proc_limit)
return 0;
- if (var_global_limit && var_global_size + size > var_global_limit)
+ if (var_global_limit && proc_vars.size + size > var_global_limit)
return 0;
}
var_accounting_diff(vars, sess, strm, size);
@@ -192,7 +193,6 @@
_HA_ATOMIC_SUB(&vars->size, size);
_HA_ATOMIC_SUB(&proc_vars.size, size);
- _HA_ATOMIC_SUB(&var_global_size, size);
}
/* This function initializes a variables list head */