From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 8 Aug 2018 21:04:50 +1000 From: Stephen Rothwell To: Kirill Tkhai Cc: akpm@linux-foundation.org, gregkh@linuxfoundation.org, rafael@kernel.org, viro@zeniv.linux.org.uk, darrick.wong@oracle.com, paulmck@linux.vnet.ibm.com, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, hughd@google.com, shuah@kernel.org, robh@kernel.org, ulf.hansson@linaro.org, aspriel@gmail.com, vivek.gautam@codeaurora.org, robin.murphy@arm.com, joe@perches.com, heikki.krogerus@linux.intel.com, vdavydov.dev@gmail.com, mhocko@suse.com, chris@chris-wilson.co.uk, penguin-kernel@I-love.SAKURA.ne.jp, aryabinin@virtuozzo.com, willy@infradead.org, ying.huang@intel.com, shakeelb@google.com, jbacik@fb.com, mingo@kernel.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH RFC 01/10] rcu: Make CONFIG_SRCU unconditionally enabled Message-ID: <20180808210450.02108372@canb.auug.org.au> In-Reply-To: <9ac119a7-4142-3a5a-6c4b-6f35ad026cb0@virtuozzo.com> References: <153365347929.19074.12509495712735843805.stgit@localhost.localdomain> <153365625652.19074.8434946780002619802.stgit@localhost.localdomain> <20180808110827.65631461@canb.auug.org.au> <9ac119a7-4142-3a5a-6c4b-6f35ad026cb0@virtuozzo.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; boundary="Sig_/NS9RdzWSmlMIFWUxGHf7hWB"; protocol="application/pgp-signature" Sender: owner-linux-mm@kvack.org List-ID: --Sig_/NS9RdzWSmlMIFWUxGHf7hWB Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Hi Kirill, On Wed, 8 Aug 2018 12:59:40 +0300 Kirill Tkhai wrote: > > On 08.08.2018 04:08, Stephen Rothwell wrote: > >=20 > > So what sort of overheads (in terms of code size and performance) are > > we adding by having SRCU enabled where it used not to be? =20 >=20 > SRCU is unconditionally enabled for x86, so I had to use another arch (sp= arc64) > to check the size difference. The config, I used to compile, is attached,= SRCU > was enabled via: >=20 > diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig > index 2d58c26bff9a..6e9116e356d4 100644 > --- a/arch/sparc/Kconfig > +++ b/arch/sparc/Kconfig > @@ -15,6 +15,7 @@ config SPARC > select ARCH_MIGHT_HAVE_PC_PARPORT if SPARC64 && PCI > select ARCH_MIGHT_HAVE_PC_SERIO > select OF > + select SRCU > select OF_PROMTREE > select HAVE_IDE > select HAVE_OPROFILE >=20 > $ size image.srcu.disabled=20 > text data bss dec hex filename > 5117546 8030506 1968104 15116156 e6a77c image.srcu.disabled >=20 > $ size image.srcu.enabled > text data bss dec hex filename > 5126175 8064346 1968104 15158625 e74d61 image.srcu.enabled >=20 > The difference is: 15158625-15116156 =3D 42469 ~41Kb Thanks for that. > I have not ideas about performance overhead measurements. If you have ide= as, > where they may occur, please say. At the first sight, there should not be > a problem, since SRCU is enabled in x86 by default. I have no idea, just asking questions that might be relevant for platforms where SRCU is normally disabled. --=20 Cheers, Stephen Rothwell --Sig_/NS9RdzWSmlMIFWUxGHf7hWB Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEENIC96giZ81tWdLgKAVBC80lX0GwFAltqzlIACgkQAVBC80lX 0Gxx3Qf7B8JdGdmyDUbzpSrVrCvYft5KUeWIit4wjayC3zqPfE6opmESJwxrGov6 ZfEobR/VNTg8r3HLAXSFgrGo0WUOdEyJwHYd1gfZZVdAevP/LzJMZ6TA8mNVQch8 /XUUGD1B4YL/sR6CNlzCPQnetJhqYxbrDDCbDM9Ek1E+ZnII4Un4or5bY4It4R66 5UaTWGuBK9T5005AkjoNXgb48F0AXA9jkprtxCD44n4hkuzr+1egFLyoonb/ZEoT s73eJN8haDVsK5gZ4CUiKQBwuNZisllJ4+L6tGvEx6pKIVtQqJYrgVLJ5Sbaz6gG qOOuGqBP07jhK/XSWTsL11dWLEe0bg== =YY9L -----END PGP SIGNATURE----- --Sig_/NS9RdzWSmlMIFWUxGHf7hWB--