From patchwork Tue Dec 17 21:47:23 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adhemerval Zanella Netto X-Patchwork-Id: 36928 Received: (qmail 111238 invoked by alias); 17 Dec 2019 21:47:53 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 111159 invoked by uid 89); 17 Dec 2019 21:47:52 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-21.9 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, SPF_PASS autolearn=ham version=3.3.1 spammy= X-HELO: mail-pj1-f67.google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:subject:date:message-id:in-reply-to:references; bh=R1BEo8/eT3/RRnCX8f6bzror1sujYwo3bSlph0ZNcTs=; b=hgSoVs8uV39fVzGRq/b09KieVYgx+wryDrkBPIG796M/3Nz2AofHZDViJwD4o2up9A VpnUMuy+MU+z0E8RgNa9WfAYabQJVSwkLPq23e0Xz/nrg5iwnMge5Bq4knJuIfVcvWNR ESjzet00unxNQGUVM8fsPboa0/TXCPsjV2+qlXjR3kUYsAZW1lOsWNTAN8seSWKW7Th8 fiD3rE0nzx5reWs1sIPYHL48L4iKOSCRu/6zJ5wKMNnhfXONzJqGzWSIrwVaIT+5gSPy K0YOvQ1PzrSONDr+z3fHTsubMw0aMIAXa6YBq7L3PCCebVRr3FQp1OqQFFbjYG5AEJbW JJWw== Return-Path: From: Adhemerval Zanella To: libc-alpha@sourceware.org Subject: [PATCH 11/16] linux: Optimize fallback 32-bit clock_gettime Date: Tue, 17 Dec 2019 18:47:23 -0300 Message-Id: <20191217214728.2886-11-adhemerval.zanella@linaro.org> In-Reply-To: <20191217214728.2886-1-adhemerval.zanella@linaro.org> References: <20191217214728.2886-1-adhemerval.zanella@linaro.org> This patch avoid probing the __NR_clock_getttime64 syscall each time __clock_gettime64 is issued on a kernel without 64 bit time support. Once ENOSYS is obtained, only 32-bit clock_gettime are used. The following snippet: clock_gettime (CLOCK_REALTIME, &(struct timespec) { 0 }); clock_gettime (CLOCK_MONOTONIC, &(struct timespec) { 0 }); clock_gettime (CLOCK_BOOTTIME, &(struct timespec) { 0 }); clock_gettime (20, &(struct timespec) { 0 }); On a kernel without 64 bit time support and with vDSO support results on the following syscalls: syscall_0x193(0, 0xff87ba30, [...]) = -1 ENOSYS (Function not implemented) clock_gettime(CLOCK_BOOTTIME, {tv_sec=927082, tv_nsec=474382032}) = 0 clock_gettime(0x14 /* CLOCK_??? */, 0xff87b9f8) = -1 EINVAL (Invalid argument) While on a kernel without vDSO support: syscall_0x193(0, 0xbec95550, 0xb6ed2000, 0x1, 0xbec95550, 0) = -1 (errno 38) clock_gettime(CLOCK_REALTIME, {tv_sec=1576615930, tv_nsec=638250162}) = 0 clock_gettime(CLOCK_MONOTONIC, {tv_sec=1665478, tv_nsec=638779620}) = 0 clock_gettime(CLOCK_BOOTTIME, {tv_sec=1675418, tv_nsec=292932704}) = 0 clock_gettime(0x14 /* CLOCK_??? */, 0xbec95530) = -1 EINVAL (Invalid argument) Checked on i686-linux-gnu on 4.15 kernel. Reviewed-by: Siddhesh Poyarekar --- sysdeps/unix/sysv/linux/clock_gettime.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/sysdeps/unix/sysv/linux/clock_gettime.c b/sysdeps/unix/sysv/linux/clock_gettime.c index 9be1f779e3..2a8ad0acc5 100644 --- a/sysdeps/unix/sysv/linux/clock_gettime.c +++ b/sysdeps/unix/sysv/linux/clock_gettime.c @@ -43,13 +43,21 @@ __clock_gettime64 (clockid_t clock_id, struct __timespec64 *tp) int r; /* Old 32-bit ABI with possible 64-bit time_t support. */ # ifdef __NR_clock_gettime64 + /* Avoid issue a __NR_clock_gettime64 syscall on kernels that do not + support 64-bit time_t. */ + static int time64_support = 1; + if (atomic_load_relaxed (&time64_support) == 1) + { # ifdef HAVE_CLOCK_GETTIME64_VSYSCALL - r = INLINE_VSYSCALL (clock_gettime64, 2, clock_id, tp); + r = INLINE_VSYSCALL (clock_gettime64, 2, clock_id, tp); # else - r = INLINE_SYSCALL_CALL (clock_gettime64, clock_id, tp); + r = INLINE_SYSCALL_CALL (clock_gettime64, clock_id, tp); # endif - if (r == 0 || errno != ENOSYS) - return r; + if (r == 0 || errno != ENOSYS) + return r; + + atomic_store_relaxed (&time64_support, 0); + } # endif /* Fallback code that uses 32-bit support. */ struct timespec tp32;