From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 5C5393858033; Tue, 13 Feb 2024 16:54:17 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 5C5393858033 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1707843257; bh=7a5EGgVkVvWGfchD9dRbNBjHYrXwu5BEKWQ/372tMvE=; h=From:To:Subject:Date:In-Reply-To:References:From; b=PSVU5smmr+4JYFP6moc417I5sMmN018jUj1nDePIVoaCjz4b8mwFO0Wat5GtvEvuI E2pAaAVoebZEfC+H7aJekFL+KEYpBteyKamafFFlQfdXzRensUEGISPHPn8W4j5URp BCUAuJ+EFkajYupM3wmqy56Mrkm0FEFr57fubK3A= From: "cvs-commit at gcc dot gnu.org" To: glibc-bugs@sourceware.org Subject: [Bug string/30994] REP MOVSB performance suffers from page aliasing on Zen 4 Date: Tue, 13 Feb 2024 16:54:16 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: glibc X-Bugzilla-Component: string X-Bugzilla-Version: 2.38 X-Bugzilla-Keywords: X-Bugzilla-Severity: minor X-Bugzilla-Who: cvs-commit at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: security- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://sourceware.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 List-Id: https://sourceware.org/bugzilla/show_bug.cgi?id=3D30994 --- Comment #13 from Sourceware Commits --- The master branch has been updated by H.J. Lu : https://sourceware.org/git/gitweb.cgi?p=3Dglibc.git;h=3D0c0d39fe4aeb0f69b26= e76337c5dfd5530d5d44e commit 0c0d39fe4aeb0f69b26e76337c5dfd5530d5d44e Author: Adhemerval Zanella Date: Thu Feb 8 10:08:38 2024 -0300 x86: Fix Zen3/Zen4 ERMS selection (BZ 30994) The REP MOVSB usage on memcpy/memmove does not show much performance improvement on Zen3/Zen4 cores compared to the vectorized loops. Also, as from BZ 30994, if the source is aligned and the destination is not the performance can be 20x slower. The performance difference is noticeable with small buffer sizes, closer to the lower bounds limits when memcpy/memmove starts to use ERMS. The performance of REP MOVSB is similar to vectorized instruction on the size limit (the L2 cache). Also, there is no drawback to multiple cores sharing the cache. Checked on x86_64-linux-gnu on Zen3. Reviewed-by: H.J. Lu --=20 You are receiving this mail because: You are on the CC list for the bug.=