From owner-freebsd-drivers@freebsd.org Wed Sep 16 07:15:11 2020 Return-Path: Delivered-To: freebsd-drivers@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id EB3B63DAE92 for ; Wed, 16 Sep 2020 07:15:11 +0000 (UTC) (envelope-from julian.grajkowski@gmail.com) Received: from mail-io1-xd2d.google.com (mail-io1-xd2d.google.com [IPv6:2607:f8b0:4864:20::d2d]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "smtp.gmail.com", Issuer "GTS CA 1O1" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4Brrvz1fHKz4MQS for ; Wed, 16 Sep 2020 07:15:11 +0000 (UTC) (envelope-from julian.grajkowski@gmail.com) Received: by mail-io1-xd2d.google.com with SMTP id r9so7182089ioa.2 for ; Wed, 16 Sep 2020 00:15:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to; bh=xZ8MuEfGNjvbyEwJl66cFUWcpjdFFvZyYHEcr8hi0jE=; b=C6duzDNvUIObFtqgpPmrTfmzSfugjo2apGtzgQXV7ILyURCML4XNqHld3bhW4PMkNm m88rq8M4LGje6Sep/7Z2UsKTdojVmPSVjIJ3sxpCmH5WcvU3QxBF8PdBDRPsNoF3hvDn S+ZQ+HL2LjDotvqRcfCgPpvB+L6eS7Yg4hVIwdauiq+fPJej0XX8jUCfSGVxdF/qgrmO HLnLiModgsoH+UofIU67eGKs2rlTK58GAiil7e0MpQzAiDFddUIlA+D9ZiYUAZlQi2jF FIlhdd6pQWUgcZdTQj2MtUl6QUtjNsVrJCg1TMUeNK5xf/HxJ1BRgpd06OZevjVt0Erd 8fxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to; bh=xZ8MuEfGNjvbyEwJl66cFUWcpjdFFvZyYHEcr8hi0jE=; b=F5bumGq/qQO3+gsxlEN3i+VViEPKqFNc0LcgzRG/gXWAFVtUeMychIqcgLk2J/kcw6 aFxLX0XPsCdFXSwDZ1rf8H7/uo7rgYeYPPFKQ6pIVx0UB/hUlU/XRIHvPtJMvHX/cmE4 dohhSnmQcM7I42N/sKT2tiLdp4DQONJbsHa7XlbIGbXoKWro5/WZVfxOIeKDCmotI/nh rlbVuVEoJK9XsP49njnP01d1AFO4kCprEtbZOcnvObv5NikHQhDt75v4vYRiKRFhWEFI xRK/+MugFtVvYBk+vpjaytHO3eSlRL3GcO6wnfAOZD/6BqOxiRYmf6PAJ4b4Sv2974Gd 98mw== X-Gm-Message-State: AOAM531Bfhy6D0wB0kKQGxQE/xFnRocR6VzmQtWJ1GPxxzPK+zk2EtZb d7k6n+RVhcvZS/E3dY4tv2EclygHvocz+A5e5dMDFB1RYg== X-Google-Smtp-Source: ABdhPJzNmzlpX4dhaH/Hnbz6OtCwA18EKDK+BqJIC7shNO79jfGtrrASLNkW55iE8xg19th9+6n7oPCckQzrNPrzZ8o= X-Received: by 2002:a5d:8e0a:: with SMTP id e10mr8824449iod.169.1600240509488; Wed, 16 Sep 2020 00:15:09 -0700 (PDT) MIME-Version: 1.0 From: Julian Grajkowski Date: Wed, 16 Sep 2020 09:14:58 +0200 Message-ID: Subject: getpid() performance To: freebsd-drivers@freebsd.org X-Rspamd-Queue-Id: 4Brrvz1fHKz4MQS X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=gmail.com header.s=20161025 header.b=C6duzDNv; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (mx1.freebsd.org: domain of juliangrajkowski@gmail.com designates 2607:f8b0:4864:20::d2d as permitted sender) smtp.mailfrom=juliangrajkowski@gmail.com X-Spamd-Result: default: False [-3.79 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.97)[-0.967]; R_DKIM_ALLOW(-0.20)[gmail.com:s=20161025]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; DWL_DNSWL_NONE(0.00)[gmail.com:dkim]; R_SPF_ALLOW(-0.20)[+ip6:2607:f8b0:4000::/36:c]; FREEMAIL_FROM(0.00)[gmail.com]; MIME_GOOD(-0.10)[multipart/alternative,text/plain]; PREVIOUSLY_DELIVERED(0.00)[freebsd-drivers@freebsd.org]; TO_DN_NONE(0.00)[]; RCPT_COUNT_ONE(0.00)[1]; NEURAL_HAM_LONG(-0.98)[-0.980]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_TRACE(0.00)[gmail.com:+]; DMARC_POLICY_ALLOW(-0.50)[gmail.com,none]; RCVD_IN_DNSWL_NONE(0.00)[2607:f8b0:4864:20::d2d:from]; NEURAL_HAM_SHORT(-0.85)[-0.846]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+,1:+,2:~]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:15169, ipnet:2607:f8b0::/32, country:US]; TAGGED_FROM(0.00)[]; MAILMAN_DEST(0.00)[freebsd-drivers]; RCVD_COUNT_TWO(0.00)[2] Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.33 X-BeenThere: freebsd-drivers@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: Writing device drivers for FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Sep 2020 07:15:12 -0000 Hi, I am working on a contiguous memory allocator which frequently calls getpid() in user space and I have noticed very poor performance of this function call. I measured this call performance using following code: inline uint64_t rdtsc_start(void) { uint32_t cycles_high; uint32_t cycles_low; asm volatile("lfence\n\t" "rdtscp\n\t" "mov %%edx, %0\n\t" "mov %%eax, %1\n\t" : "=r" (cycles_high), "=r" (cycles_low) : : "%rax", "%rdx", "%rcx"); return (((uint64_t)cycles_high << 32) | cycles_low); } inline uint64_t rdtsc_end(void) { uint32_t cycles_high; uint32_t cycles_low; asm volatile("rdtscp\n\t" "mov %%edx, %0\n\t" "mov %%eax, %1\n\t" "lfence\n\t" : "=r" (cycles_high), "=r" (cycles_low) : : "%rax", "%rdx", "%rcx"); return (((uint64_t)cycles_high << 32) | cycles_low); } This way I measured ~320 cycles used for getpid() on FreeBSD 12.1. For comparison, in Linux (CentOS 7) this call uses ~10 cycles. I am aware that this should not be compared directly. as these are different systems, but such a big difference in performance is an issue for me, as getpid() is called very often in my code. Is such a poor performance of getpid() a known problem and is it possible that this might be improved in future releases? Measurements were done on the same mahcine with following setup: CPU: Intel(R) Atom(TM) CPU C3958 @ 2.00GHz (2000.06-MHz K8-class CPU) FreeBSD/SMP: Multiprocessor System Detected: 16 CPUs 8GB RAM (2x4GB): Type: DDR4 Type Detail: Synchronous Unbuffered (Unregistered) Speed: 2400 MT/s Thank you very much in advance for any help. Kind regards, Julian