From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:60321) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ehdO5-0004p8-Lb for qemu-devel@nongnu.org; Fri, 02 Feb 2018 10:37:31 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ehdKD-00037w-Dz for qemu-devel@nongnu.org; Fri, 02 Feb 2018 10:36:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58318) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ehdKC-00035B-Bb for qemu-devel@nongnu.org; Fri, 02 Feb 2018 10:32:24 -0500 From: Markus Armbruster Date: Fri, 2 Feb 2018 14:03:23 +0100 Message-Id: <20180202130336.24719-9-armbru@redhat.com> In-Reply-To: <20180202130336.24719-1-armbru@redhat.com> References: <20180202130336.24719-1-armbru@redhat.com> Subject: [Qemu-devel] [PATCH RFC 08/21] qapi: Touch generated files only when they change List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: marcandre.lureau@redhat.com, eblake@redhat.com, mdroth@linux.vnet.ibm.com A massive number of objects depends on QAPI-generated headers. In my "build everything" tree, it's roughly 4500 out of 4800. This is particularly annoying when only some of the generated files change, say for a doc fix. Improve qapi-gen.py to touch its output files only if they actually change. Rebuild time for a QAPI doc fix drops from many minutes to a few seconds. Rebuilds get faster for certain code changes, too. For instance, adding a simple QMP event now recompiles less than 200 instead of 4500 objects. But adding a QAPI type is as bad as ever; we clearly got more work to do. Signed-off-by: Markus Armbruster --- scripts/qapi/common.py | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py index cfa2671ca3..be0fcc548a 100644 --- a/scripts/qapi/common.py +++ b/scripts/qapi/common.py @@ -1944,9 +1944,16 @@ class QAPIGen(object): except os.error as e: if e.errno != errno.EEXIST: raise - f = open(os.path.join(output_dir, fname), 'w') - f.write(self.top(fname) + self._preamble + self._body + fd = os.open(os.path.join(output_dir, fname), + os.O_RDWR | os.O_CREAT, 0666) + f = os.fdopen(fd, 'r+') + text = (self.top(fname) + self._preamble + self._body + self.bottom(fname)) + oldtext = f.read(len(text) + 1) + if text != oldtext: + f.seek(0) + f.truncate(0) + f.write(text) f.close() -- 2.13.6