From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 42A3AC3F2D2 for ; Mon, 2 Mar 2020 09:29:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0A2B9246B4 for ; Mon, 2 Mar 2020 09:29:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="vORyykoE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727323AbgCBJ3S (ORCPT ); Mon, 2 Mar 2020 04:29:18 -0500 Received: from mail-pg1-f195.google.com ([209.85.215.195]:36903 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727107AbgCBJ3S (ORCPT ); Mon, 2 Mar 2020 04:29:18 -0500 Received: by mail-pg1-f195.google.com with SMTP id z12so5148377pgl.4 for ; Mon, 02 Mar 2020 01:29:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=PMfx9+p6QDhZVTfguad7WF1IY4mPzVo4yyasHAMM2CQ=; b=vORyykoEQhKoPiyvuJ0B+U5Ui23zAm5CzFb+BcpqMqF9wdmGN9hyF88/EYGxb1aiaE SkKUJhol5DQk+8nqLDLfsEulb8VheqZOdpYqw5CcAkjjyCNsAk7ScYLio1jZFvhaRcze mSFVvNJvxXqCgvU1BEXgmPQYQQm+0YKblYimiG7Pc73jtCPA8s9EAreMBEioSDTiqB6Q tWm7RaIWtAH5T39OWCr0Cg3QCGEwN2iauUFmAMwaXkVetArn/XUjQwyTfMRcUT2iSvHx iOf+EKgdQIUgy/0S2wBwzAjGHw+eAD+/xv7Bc0bG8qq8yqINbgg+uWYQrbhXKaEoUGQU DUNw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=PMfx9+p6QDhZVTfguad7WF1IY4mPzVo4yyasHAMM2CQ=; b=h0KKETal6KpPCiYDcqSMOuxPXl0VJ/O1eV3Vjai0Hbb3XDoEm7ZcwrF10TGSjPavCa hm8OVRd5iiiW3jMUxUJH9RfjxJbysbeFw0l2t3JEw8u0r512XIOfKp9cakxwUMLUtlV3 xJOhHWPk6Zpzg92V/0GXxlq95pBBEJo/nvXeLRonJ4RY3n4kQ2CI0s3XRWZJ2V6Uw8MZ HsuAcDmazhiI6lTfMniN+n4exQbdA//83FvcYFSusI+VG07GkW1R7qCiu/06Z8ZEE1iy jnxmFoxD7/88rONeE0Ba2x90qM3YVnyXplc0Gd+Z7rGqwRveLCGeDtRp1zXy5CwZ4njs 90Iw== X-Gm-Message-State: APjAAAW/dWaWvaZumyBeeU1W6xQXNjPhqJoojyN/EDRFzVS/cBY0FcAx wv6mK3FZv/w2zSFze8dNzRO7deCZdpgpOeyAUAoKAhgi X-Google-Smtp-Source: APXvYqz0aElQRmCga/bF7+Afc8iUlcO1TsXiAWWB2nAnSGIpjzI7MpkNuM4KB4deLKgvvFmPsgaKHbM0aufNQFzgTSY= X-Received: by 2002:a62:7ccc:: with SMTP id x195mr15135925pfc.71.1583141357115; Mon, 02 Mar 2020 01:29:17 -0800 (PST) MIME-Version: 1.0 References: <20200227142001.61577-1-tz.stoyanov@gmail.com> <20200227142001.61577-4-tz.stoyanov@gmail.com> <20200227122303.25dacb7b@gandalf.local.home> In-Reply-To: <20200227122303.25dacb7b@gandalf.local.home> From: Tzvetomir Stoyanov Date: Mon, 2 Mar 2020 11:29:05 +0200 Message-ID: Subject: Re: [PATCH v20 03/15] trace-cmd: Find and store pids of tasks, which run virtual CPUs of given VM To: Steven Rostedt Cc: linux-trace-devel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-trace-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org On Thu, Feb 27, 2020 at 7:23 PM Steven Rostedt wrote: > > On Thu, 27 Feb 2020 16:19:49 +0200 > "Tzvetomir Stoyanov (VMware)" wrote: > > > From: Tzvetomir Stoyanov > > > > In order to match host and guest events, a mapping between guest VCPU > > and the host task, running this VCPU is needed. Extended existing > > struct guest to hold such mapping and added logic in read_qemu_guests() > > function to initialize it. Implemented a new internal API, > > get_guest_vcpu_pid(), to retrieve VCPU-task mapping for given VM. > > > > Signed-off-by: Tzvetomir Stoyanov > > --- > > tracecmd/include/trace-local.h | 2 + > > tracecmd/trace-record.c | 77 ++++++++++++++++++++++++++++++++++ > > 2 files changed, 79 insertions(+) > > > > diff --git a/tracecmd/include/trace-local.h b/tracecmd/include/trace-local.h > > index 29f27793..a5cf0640 100644 > > --- a/tracecmd/include/trace-local.h > > +++ b/tracecmd/include/trace-local.h > > @@ -247,6 +247,8 @@ void update_first_instance(struct buffer_instance *instance, int topt); > > > > void show_instance_file(struct buffer_instance *instance, const char *name); > > > > +int get_guest_vcpu_pid(unsigned int guest_cid, unsigned int guest_vcpu); > > + > > /* moved from trace-cmd.h */ > > void tracecmd_create_top_instance(char *name); > > void tracecmd_remove_instances(void); > > diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c > > index 28fe31b7..4370c964 100644 > > --- a/tracecmd/trace-record.c > > +++ b/tracecmd/trace-record.c > > @@ -3035,11 +3035,30 @@ struct guest { > > char *name; > > int cid; > > int pid; > > + int cpu_max; > > + int *cpu_pid; > > }; > > > > static struct guest *guests; > > static size_t guests_len; > > > > +static int set_vcpu_pid_mapping(struct guest *guest, int cpu, int pid) > > +{ > > + int *cpu_pid; > > + > > + if (cpu < 0 || pid < 0) > > + return -1; > > This check makes the check before its call not needed (see below). > > > + if (cpu >= guest->cpu_max) { > > + cpu_pid = realloc(guest->cpu_pid, (cpu + 1) * sizeof(int)); > > It is possible that the cpu numbers may be sparse, which means we should we > should probably initialize the new numbers as... > > > + if (!cpu_pid) > > + return -1; > > /* Handle sparse CPU numbers */ > for (i = guest->cpu_max; i < cpu; i++) > guest->cpu_pid[i] = -1; > > Note, the above wont loop at all if there's no sparse CPUs (missing > numbers). > > > + guest->cpu_max = cpu + 1; > > + guest->cpu_pid = cpu_pid; > > + } > > + guest->cpu_pid[cpu] = pid; > > + return 0; > > +} > > + > > static char *get_qemu_guest_name(char *arg) > > { > > char *tok, *end = arg; > > @@ -3052,6 +3071,46 @@ static char *get_qemu_guest_name(char *arg) > > return arg; > > } > > > > +static void read_qemu_guests_pids(char *guest_task, struct guest *guest) > > Probably should return a status. > > > +{ > > + struct dirent *entry; > > + char path[PATH_MAX]; > > + char *buf = NULL; > > + size_t n = 0; > > + long int vcpu; > > + long int pid; > > "int" is not needed. Just "long" is good enough. > > long vcpu; > long pid; > > Although, I doubt there will be more than 4 billion of either of these, so > they should probably be just "int". Which means you don't need the INT_MAX > checks. > The reason I use long is strtol(), which returns long integer. In case of an error, this API returns LONG_MAX or LONG_MIN. The set_vcpu_pid_mapping() accepts int, that's why I put these checks - to filter possible strtol() parsing errors and int overflow. I'll keep the checks and remove the duplicated ones in set_vcpu_pid_mapping() > > + DIR *dir; > > + FILE *f; > > + > > + snprintf(path, sizeof(path), "/proc/%s/task", guest_task); > > + dir = opendir(path); > > + if (!dir) > > + return; > > + > > + while ((entry = readdir(dir))) { > > + if (!(entry->d_type == DT_DIR && is_digits(entry->d_name))) > > + continue; > > + > > + snprintf(path, sizeof(path), "/proc/%s/task/%s/comm", > > + guest_task, entry->d_name); > > + f = fopen(path, "r"); > > + if (!f) > > + continue; > > + > > + if (getline(&buf, &n, f) >= 0 && > > + strncmp(buf, "CPU ", 4) == 0) { > > + vcpu = strtol(buf + 4, NULL, 10); > > + pid = strtol(entry->d_name, NULL, 10); > > + if (vcpu < INT_MAX && pid < INT_MAX && > > + vcpu >= 0 && pid >= 0) > > The vcpu >= 0 && pid >= 0 are not needed due to the check in the function. > > > + set_vcpu_pid_mapping(guest, vcpu, pid); > > Probably should check the return status of this function, and report a > warning if it fails. > > > + } > > + > > + fclose(f); > > + } > > + free(buf); > > +} > > + > > static void read_qemu_guests(void) > > { > > static bool initialized; > > @@ -3115,6 +3174,8 @@ static void read_qemu_guests(void) > > if (!is_qemu) > > goto next; > > > > + read_qemu_guests_pids(entry->d_name, &guest); > > Should probably check the status of the above function. Die on error? I'll put a warning, as this failure is not critical - the guest tracing will still work, even without this mapping. Thanks, Steven! > > > + > > guests = realloc(guests, (guests_len + 1) * sizeof(*guests)); > > if (!guests) > > die("Can not allocate guest buffer"); > > @@ -3160,6 +3221,22 @@ static char *parse_guest_name(char *guest, int *cid, int *port) > > return guest; > > } > > > > +int get_guest_vcpu_pid(unsigned int guest_cid, unsigned int guest_vcpu) > > +{ > > + int i; > > + > > + if (!guests) > > + return -1; > > + > > + for (i = 0; i < guests_len; i++) { > > + if (!guests[i].cpu_pid || guest_vcpu >= guests[i].cpu_max) > > As a cpu_pid may be zero (unlikely), and the code I showed above > initialized sparse cpus as -1, then this should be guests[i].cpu_pid < 0. > > -- Steve > > > + continue; > > + if (guest_cid == guests[i].cid) > > + return guests[i].cpu_pid[guest_vcpu]; > > + } > > + return -1; > > +} > > + > > static void set_prio(int prio) > > { > > struct sched_param sp; > -- Tzvetomir (Ceco) Stoyanov VMware Open Source Technology Center