From: Eugene Syromyatnikov <evgsyr@gmail.com>
Date: Sun, 13 Oct 2019 14:35:53 +0000 (+0200)
Subject: defs.h: compact struct tcb a bit by moving currpers field
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=49aa9bcfb34ef8dae7d49a27b86cadd1a6c382ac;p=strace

defs.h: compact struct tcb a bit by moving currpers field

As reported by pahole, struct tcb has size of 328 bytes and 8 bytes
of holes on x86_64; by moving currpers after qual_flg, both holes are
leminated and the structure fits into 8 cache lines now.  This should
also benefit other 64-bit architectures.

* defs.h [SUPPORTED_PERSONALITIES > 1] (struct tcb): Move currpers field
after qual_flg field.
---

diff --git a/defs.h b/defs.h
index 5be982ac..db1de7d4 100644
--- a/defs.h
+++ b/defs.h
@@ -251,13 +251,13 @@ struct tcb {
 	int flags;		/* See below for TCB_ values */
 	int pid;		/* If 0, this tcb is free */
 	int qual_flg;		/* qual_flags[scno] or DEFAULT_QUAL_FLAGS + RAW */
+# if SUPPORTED_PERSONALITIES > 1
+	unsigned int currpers;	/* Personality at the time of scno update */
+# endif
 	unsigned long u_error;	/* Error code */
 	kernel_ulong_t scno;	/* System call number */
 	kernel_ulong_t u_arg[MAX_ARGS];	/* System call arguments */
 	kernel_long_t u_rval;	/* Return value */
-# if SUPPORTED_PERSONALITIES > 1
-	unsigned int currpers;	/* Personality at the time of scno update */
-# endif
 	int sys_func_rval;	/* Syscall entry parser's return value */
 	int curcol;		/* Output column for this process */
 	FILE *outf;		/* Output file for this process */