From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52087) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZwyMS-0007nT-SC for qemu-devel@nongnu.org; Thu, 12 Nov 2015 15:20:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZwyMN-0001FX-SM for qemu-devel@nongnu.org; Thu, 12 Nov 2015 15:20:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54202) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZwyMN-0001FT-KI for qemu-devel@nongnu.org; Thu, 12 Nov 2015 15:20:43 -0500 References: <5641BA7B.4050108@redhat.com> <56445141.2070907@redhat.com> <5644561C.3060208@redhat.com> <56445FAB.80906@redhat.com> <87tworqwnk.fsf@emacs.mitica> <20151112195609.GD11416@work-vm> From: Eric Blake Message-ID: <5644F495.5050706@redhat.com> Date: Thu, 12 Nov 2015 13:20:37 -0700 MIME-Version: 1.0 In-Reply-To: <20151112195609.GD11416@work-vm> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="TuKBVSROxAR5npG3BM6v4tL5QT8MBjb42" Subject: Re: [Qemu-devel] [v2 0/2] add avx2 instruction optimization List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" , "Li, Liang Z" Cc: "amit.shah@redhat.com" , Paolo Bonzini , "quintela@redhat.com" , "qemu-devel@nongnu.org" , "mst@redhat.com" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --TuKBVSROxAR5npG3BM6v4tL5QT8MBjb42 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 11/12/2015 12:56 PM, Dr. David Alan Gilbert wrote: >> One thing I still can't understand, why the unit test in host environm= ent shows >> 'memcmp()' have better performance? Have you tried running under a profiler, to see if there are hotspots or at least get an idea of where the time is being spent? >=20 > Are you aware of any program other than QEMU that also wants to do some= thing > similar? Finding whether a block of memory is zero, sounds like someth= ing > that would be useful in lots of places, I just can't think which ones. At least dd, cp, and probably several other utilities. It would be nice to post an RFE to glibc to see if they can come up with a dedicated interface that is faster than memcmp(), although that still only helps us when targetting a system new enough to have that interface. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --TuKBVSROxAR5npG3BM6v4tL5QT8MBjb42 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJWRPSVAAoJEKeha0olJ0NqzFYH/26oxJ7tNIP3MQx/wYW1/hL+ 47XdCV7Q06EXFybxHwAbmwTZk9A+mThdddvRGIy2ItZsZCis8Y8weo9FRBPWHdsH A9N37ISp666DI0gkmY4M4Ic35tvduuWrqW5ZA6x+vOeuxXmvI1DTWleKrij0C43f unuzQ1WwW67NDp8zzjjLctOBtg1jXHuVsBNhTTme5mz83nqKWGsTDHiRxTyzBfXh gqxT5YLiMh1ZNzkwwr/UH4pGr/+1ckIeHY9TBB6MVQE3hSpc+kge03WjiK3mqhs7 D8g15f1Uf3fHL9gHb+rxkhB8eVQtwLaye4F2foWbyJkHYCR80t1EXxxN1YiFPhc= =MW3G -----END PGP SIGNATURE----- --TuKBVSROxAR5npG3BM6v4tL5QT8MBjb42--