From patchwork Wed Oct 11 08:35:02 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Santosh Sivaraj X-Patchwork-Id: 824286 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [103.22.144.68]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3yBnQh4wFSz9t3H for ; Wed, 11 Oct 2017 19:37:00 +1100 (AEDT) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=fossix-org.20150623.gappssmtp.com header.i=@fossix-org.20150623.gappssmtp.com header.b="skp6amif"; dkim-atps=neutral Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 3yBnQh39pLzDr5x for ; Wed, 11 Oct 2017 19:37:00 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=fossix-org.20150623.gappssmtp.com header.i=@fossix-org.20150623.gappssmtp.com header.b="skp6amif"; dkim-atps=neutral X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=fossix.org (client-ip=2607:f8b0:400e:c05::244; helo=mail-pg0-x244.google.com; envelope-from=santosh@fossix.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=fossix-org.20150623.gappssmtp.com header.i=@fossix-org.20150623.gappssmtp.com header.b="skp6amif"; dkim-atps=neutral Received: from mail-pg0-x244.google.com (mail-pg0-x244.google.com [IPv6:2607:f8b0:400e:c05::244]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3yBnNd0GR1zDr5S for ; Wed, 11 Oct 2017 19:35:12 +1100 (AEDT) Received: by mail-pg0-x244.google.com with SMTP id u144so1490463pgb.3 for ; Wed, 11 Oct 2017 01:35:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fossix-org.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id; bh=z4hWkqr3RVU4mZ8b6uQDVM0ZfqTXxCMrX43OBS4YnWw=; b=skp6amifXbLvGmneArm/wHxxJeDbSfnovCk+7Vki2GBSOKBxmEY4HAXSsrPM7qyMe1 8uqnX2uEAbNXiMkfYqy4hRhjYVSiHUINK19jg6NudkV86E9HegrCwcZBAbq86zRLsJjJ 2ghI5/keZ4bHER8llRx2PzpleTLvyPaLjsBT6ixrfy9qleobRfZfRDWJ7vbxDwrUSf/i 6BXKA8nlz0kNYjD3NKDnd3cy/cYu7eNP83vkRLY4wj1ZGY4j2+BnQjiQCJS4ri2EtFc2 3BsyvvOxrC8y5P7lOj/Z2Vpymc+Lw+IhDII5gGJM61F4LkzZVbDZqUXJh7H0no3AfI2m kgUg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=z4hWkqr3RVU4mZ8b6uQDVM0ZfqTXxCMrX43OBS4YnWw=; b=n7KDp3hll5VyZPY9wfyQCbgk06D9pR8QHpkfn7eR7AI0ZHeZV8CdlvCJwv4UUxD9ya AdQvFTNdYjspz5fHhsqje681/Uwd4hFVhmWGOcoaBIy/ve4FMc5vlHI0pUMebdIvIJ4u omkOwuKNi7yqEXSI+sCJ4B4iUDT62siCrHsuZa93IK49pSBwLpgomH/SXSUvlXW9UgXE y/M4/tIqlYrBDE7f95YgeIkvwueD07HrOico/uenbMnuJcTAMU5ANbL1Lbv/f7BfOCtI /M2I4iFyI/1ZR5gBE1/WDxMltW1dr7WX6rDq3em4U1sGxKGEMO49dNqDk9TqUgzMR1um n8Fw== X-Gm-Message-State: AMCzsaUGWbaVWPeeQEVmdSjtimCVG0QxstyygZ2eEmLQQjpKl4GOXt7t 4xi0pmbZRFMKhKWy0TOh3hru1kpFTpk= X-Google-Smtp-Source: AOwi7QBiZRhC/RARdJI8PvkiKRdooD2dKaKSn5niuTLM1A4c1DmapyMmYYhvZp0UPqi4J622C8MR6g== X-Received: by 10.98.186.11 with SMTP id k11mr1138422pff.141.1507710910376; Wed, 11 Oct 2017 01:35:10 -0700 (PDT) Received: from santosiv.in.ibm.com ([125.16.167.56]) by smtp.gmail.com with ESMTPSA id k10sm19173883pgq.92.2017.10.11.01.35.07 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 11 Oct 2017 01:35:09 -0700 (PDT) From: Santosh Sivaraj To: linuxppc-dev , "Naveen N. Rao" Subject: [PATCH v5] powerpc/vdso64: Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE Date: Wed, 11 Oct 2017 14:05:02 +0530 Message-Id: <20171011083502.11648-1-santosh@fossix.org> X-Mailer: git-send-email 2.13.6 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.24 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Srikar Dronamraju , John Stultz , Thomas Gleixner , Frederic Weisbecker Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Current vDSO64 implementation does not have support for coarse clocks (CLOCK_MONOTONIC_COARSE, CLOCK_REALTIME_COARSE), for which it falls back to system call, increasing the response time, vDSO implementation reduces the cycle time. Below is a benchmark of the difference in execution times. (Non-coarse clocks are also included just for completion) clock-gettime-realtime: syscall: 172 nsec/call clock-gettime-realtime: libc: 28 nsec/call clock-gettime-realtime: vdso: 22 nsec/call clock-gettime-monotonic: syscall: 171 nsec/call clock-gettime-monotonic: libc: 30 nsec/call clock-gettime-monotonic: vdso: 25 nsec/call clock-gettime-realtime-coarse: syscall: 153 nsec/call clock-gettime-realtime-coarse: libc: 16 nsec/call clock-gettime-realtime-coarse: vdso: 10 nsec/call clock-gettime-monotonic-coarse: syscall: 167 nsec/call clock-gettime-monotonic-coarse: libc: 17 nsec/call clock-gettime-monotonic-coarse: vdso: 11 nsec/call CC: Benjamin Herrenschmidt Signed-off-by: Santosh Sivaraj Reviewed-by: Naveen N. Rao --- Changelog: v1: - gettimeofday was moved from asm to C - Coarse timer support addition v2: - Moved Syscall fallback from inline assembly back to its original place in __kernel_clock_gettime v3: - Based on Ben's input, coarse timer support was added in assembly itself - Dropped idea of conversion to C due to the vdso update_count variable being optimized out in C v4: - Based on Naveen's comments restructured code to avoid a duplicate code block v5: - Skip creating dependency for registers that are not used for CLOCK_REALTIME_COARSE (Naveen) - Reorder instructions to get proper dependency setup (Naveen) arch/powerpc/kernel/asm-offsets.c | 2 + arch/powerpc/kernel/vdso64/gettimeofday.S | 68 ++++++++++++++++++++++++++----- 2 files changed, 59 insertions(+), 11 deletions(-) diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 8cfb20e38cfe..b55c68c54dc1 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -396,6 +396,8 @@ int main(void) /* Other bits used by the vdso */ DEFINE(CLOCK_REALTIME, CLOCK_REALTIME); DEFINE(CLOCK_MONOTONIC, CLOCK_MONOTONIC); + DEFINE(CLOCK_REALTIME_COARSE, CLOCK_REALTIME_COARSE); + DEFINE(CLOCK_MONOTONIC_COARSE, CLOCK_MONOTONIC_COARSE); DEFINE(NSEC_PER_SEC, NSEC_PER_SEC); DEFINE(CLOCK_REALTIME_RES, MONOTONIC_RES_NSEC); diff --git a/arch/powerpc/kernel/vdso64/gettimeofday.S b/arch/powerpc/kernel/vdso64/gettimeofday.S index 382021324883..058e7c24f670 100644 --- a/arch/powerpc/kernel/vdso64/gettimeofday.S +++ b/arch/powerpc/kernel/vdso64/gettimeofday.S @@ -64,6 +64,12 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime) cmpwi cr0,r3,CLOCK_REALTIME cmpwi cr1,r3,CLOCK_MONOTONIC cror cr0*4+eq,cr0*4+eq,cr1*4+eq + + cmpwi cr5,r3,CLOCK_REALTIME_COARSE + cmpwi cr6,r3,CLOCK_MONOTONIC_COARSE + cror cr5*4+eq,cr5*4+eq,cr6*4+eq + + cror cr0*4+eq,cr0*4+eq,cr5*4+eq bne cr0,99f mflr r12 /* r12 saves lr */ @@ -72,6 +78,7 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime) bl V_LOCAL_FUNC(__get_datapage) /* get data page */ lis r7,NSEC_PER_SEC@h /* want nanoseconds */ ori r7,r7,NSEC_PER_SEC@l + beq cr5,70f 50: bl V_LOCAL_FUNC(__do_get_tspec) /* get time from tb & kernel */ bne cr1,80f /* if not monotonic, all done */ @@ -97,19 +104,58 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime) ld r0,CFG_TB_UPDATE_COUNT(r3) cmpld cr0,r0,r8 /* check if updated */ bne- 50b + b 78f - /* Add wall->monotonic offset and check for overflow or underflow. + /* + * For coarse clocks we get data directly from the vdso data page, so + * we don't need to call __do_get_tspec, but we still need to do the + * counter trick. */ - add r4,r4,r6 - add r5,r5,r9 - cmpd cr0,r5,r7 - cmpdi cr1,r5,0 - blt 1f - subf r5,r7,r5 - addi r4,r4,1 -1: bge cr1,80f - addi r4,r4,-1 - add r5,r5,r7 +70: ld r8,CFG_TB_UPDATE_COUNT(r3) + andi. r0,r8,1 /* pending update ? loop */ + bne- 70b + xor r0,r8,r8 /* create dependency */ + add r3,r3,r0 + + /* + * CLOCK_REALTIME_COARSE, below values are needed for MONOTONIC_COARSE + * too + */ + ld r4,STAMP_XTIME+TSPC64_TV_SEC(r3) + ld r5,STAMP_XTIME+TSPC64_TV_NSEC(r3) + bne cr6,75f + + /* CLOCK_MONOTONIC_COARSE */ + lwa r6,WTOM_CLOCK_SEC(r3) + lwa r9,WTOM_CLOCK_NSEC(r3) + + /* check if counter has updated */ + or r0,r6,r9 +75: or r0,r0,r4 + or r0,r0,r5 + xor r0,r0,r0 + add r3,r3,r0 + ld r0,CFG_TB_UPDATE_COUNT(r3) + cmpld cr0,r0,r8 /* check if updated */ + bne- 70b + + /* Counter has not updated, so continue calculating proper values for + * sec and nsec if monotonic coarse, or just return with the proper + * values for realtime. + */ + bne cr6,80f + + /* Add wall->monotonic offset and check for overflow or underflow */ +78: add r4,r4,r6 + add r5,r5,r9 + cmpd cr0,r5,r7 + cmpdi cr1,r5,0 + blt 79f + subf r5,r7,r5 + addi r4,r4,1 +79: bge cr1,80f + addi r4,r4,-1 + add r5,r5,r7 80: std r4,TSPC64_TV_SEC(r11) std r5,TSPC64_TV_NSEC(r11)