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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 EBA4AC47254 for ; Tue, 5 May 2020 09:18:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BB4D7206B9 for ; Tue, 5 May 2020 09:18:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="a8jAlpX2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728627AbgEEJSt (ORCPT ); Tue, 5 May 2020 05:18:49 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:57279 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727931AbgEEJSt (ORCPT ); Tue, 5 May 2020 05:18:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588670327; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zuMGxsvybi8NjrS2E9p5tIYiMOdSBLcmmuty15NCl3s=; b=a8jAlpX2OgkAjKjZ0SMA+T/46LAjEUwU5wDzR272oqmoNLTNBxkLAIIDORGlgnAhBSD6OH Dg0xiGTXRvJmEWGJ95tgTHOgwA9LZbXkL4fE6UIKcOcs5VI7qMiDSauOCdVSCtTrU/m4/n hqMovwsAxVnrPaTN/ZpT3x44XCGql00= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-149-ojzvjG1dP7--JR39eUzu4A-1; Tue, 05 May 2020 05:18:43 -0400 X-MC-Unique: ojzvjG1dP7--JR39eUzu4A-1 Received: by mail-wr1-f71.google.com with SMTP id x8so907198wrl.16 for ; Tue, 05 May 2020 02:18:43 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=zuMGxsvybi8NjrS2E9p5tIYiMOdSBLcmmuty15NCl3s=; b=iywhruR0b1KQhrjZursFFHVuBV6LhOK4eIAQ4XRHaNG+mGoKpsAkfP4F9u5S8RgN/4 9mbsds+nSagFxw4gdd1HdsRSDmUMbr/zRde+jczCBArbeJdGO7LoHISlA3PzVaZqJDjp sd/gMT1tB4++p95LmEXTiQ7kY0WmsuPDvzcWSkN8Ql/U55hP7P1DRZQi57aP2341Szuc armOADxxbie3diWFIvc7R9j8SN2JLXWNzRaU+3HdTOh3dLs3bnTXO7vM4MVRK+Vif+9m 6Lugw4Nr/3MU3fy0wq37Wkw6ksNwGS/hcMOQPsFypUohInbleQMcT6pSEzX4SSSEgHGg tkNg== X-Gm-Message-State: AGi0PuYND9+Gd9vcpSILVNwTN7qbQKocBw5iTLRTK5DsZaW1LE+dwdCt 2EiLgCVs3AgyCHypGHkEn0f4bgzQu1mN5QMRUvY3ZCX6s4VHA/EbWNWLr5uMn/pY16oXQhIxEg0 DPvYokzEsqLo1dOgzBgeJRQiX X-Received: by 2002:adf:fc92:: with SMTP id g18mr2673629wrr.10.1588670322685; Tue, 05 May 2020 02:18:42 -0700 (PDT) X-Google-Smtp-Source: APiQypKX7pVuROFVyxwt8yc6FBoonk6++mD6BpR68uHXCtbveK9HdmTEsxgnCte+p9bp4Db4rFjGdw== X-Received: by 2002:adf:fc92:: with SMTP id g18mr2673592wrr.10.1588670322377; Tue, 05 May 2020 02:18:42 -0700 (PDT) Received: from localhost.localdomain ([194.230.155.186]) by smtp.gmail.com with ESMTPSA id n6sm2246200wrs.81.2020.05.05.02.18.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 May 2020 02:18:41 -0700 (PDT) Subject: Re: [PATCH v2 0/5] Statsfs: a new ram-based file sytem for Linux kernel statistics To: David Rientjes Cc: Jonathan Adams , kvm@vger.kernel.org, Christian Borntraeger , David Hildenbrand , Cornelia Huck , Paolo Bonzini , Vitaly Kuznetsov , Jim Mattson , Alexander Viro , Emanuele Giuseppe Esposito , linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20200504110344.17560-1-eesposit@redhat.com> From: Emanuele Giuseppe Esposito Message-ID: Date: Tue, 5 May 2020 11:18:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/4/20 11:37 PM, David Rientjes wrote: > On Mon, 4 May 2020, Emanuele Giuseppe Esposito wrote: > >> >> In this patch series I introduce statsfs, a synthetic ram-based virtual >> filesystem that takes care of gathering and displaying statistics for the >> Linux kernel subsystems. >> > > This is exciting, we have been looking in the same area recently. Adding > Jonathan Adams . > > In your diffstat, one thing I notice that is omitted: an update to > Documentation/* :) Any chance of getting some proposed Documentation/ > updates with structure of the fs, the per subsystem breakdown, and best > practices for managing the stats from the kernel level? Yes, I will write some documentation. Thank you for the suggestion. >> >> Values represent quantites that are gathered by the statsfs user. Examples >> of values include the number of vm exits of a given kind, the amount of >> memory used by some data structure, the length of the longest hash table >> chain, or anything like that. Values are defined with the >> statsfs_source_add_values function. Each value is defined by a struct >> statsfs_value; the same statsfs_value can be added to many different >> sources. A value can be considered "simple" if it fetches data from a >> user-provided location, or "aggregate" if it groups all values in the >> subordinates sources that include the same statsfs_value. >> > > This seems like it could have a lot of overhead if we wanted to > periodically track the totality of subsystem stats as a form of telemetry > gathering from userspace. To collect telemetry for 1,000 different stats, > do we need to issue lseek()+read() syscalls for each of them individually > (or, worse, open()+read()+close())? > > Any thoughts on how that can be optimized? A couple of ideas: > > - an interface that allows gathering of all stats for a particular > interface through a single file that would likely be encoded in binary > and the responsibility of userspace to disseminate, or > > - an interface that extends beyond this proposal and allows the reader to > specify which stats they are interested in collecting and then the > kernel will only provide these stats in a well formed structure and > also be binary encoded. Are you thinking of another file, containing all the stats for the directory in binary format? > We've found that the one-file-per-stat method is pretty much a show > stopper from the performance view and we always must execute at least two > syscalls to obtain a single stat. > > Since this is becoming a generic API (good!!), maybe we can discuss > possible ways to optimize gathering of stats in mass? Sure, the idea of a binary format was considered from the beginning in [1], and it can be done either together with the current filesystem, or as a replacement via different mount options. Thank you, Emanuele >> [1] https://lore.kernel.org/kvm/5d6cdcb1-d8ad-7ae6-7351-3544e2fa366d@redhat.com/?fbclid=IwAR18LHJ0PBcXcDaLzILFhHsl3qpT3z2vlG60RnqgbpGYhDv7L43n0ZXJY8M >> >> Signed-off-by: Emanuele Giuseppe Esposito >> >> v1->v2 remove unnecessary list_foreach_safe loops, fix wrong indentation, >> change statsfs in stats_fs >> >> Emanuele Giuseppe Esposito (5): >> refcount, kref: add dec-and-test wrappers for rw_semaphores >> stats_fs API: create, add and remove stats_fs sources and values >> kunit: tests for stats_fs API >> stats_fs fs: virtual fs to show stats to the end-user >> kvm_main: replace debugfs with stats_fs >> >> MAINTAINERS | 7 + >> arch/arm64/kvm/Kconfig | 1 + >> arch/arm64/kvm/guest.c | 2 +- >> arch/mips/kvm/Kconfig | 1 + >> arch/mips/kvm/mips.c | 2 +- >> arch/powerpc/kvm/Kconfig | 1 + >> arch/powerpc/kvm/book3s.c | 6 +- >> arch/powerpc/kvm/booke.c | 8 +- >> arch/s390/kvm/Kconfig | 1 + >> arch/s390/kvm/kvm-s390.c | 16 +- >> arch/x86/include/asm/kvm_host.h | 2 +- >> arch/x86/kvm/Kconfig | 1 + >> arch/x86/kvm/Makefile | 2 +- >> arch/x86/kvm/debugfs.c | 64 -- >> arch/x86/kvm/stats_fs.c | 56 ++ >> arch/x86/kvm/x86.c | 6 +- >> fs/Kconfig | 12 + >> fs/Makefile | 1 + >> fs/stats_fs/Makefile | 6 + >> fs/stats_fs/inode.c | 337 ++++++++++ >> fs/stats_fs/internal.h | 35 + >> fs/stats_fs/stats_fs-tests.c | 1088 +++++++++++++++++++++++++++++++ >> fs/stats_fs/stats_fs.c | 773 ++++++++++++++++++++++ >> include/linux/kref.h | 11 + >> include/linux/kvm_host.h | 39 +- >> include/linux/refcount.h | 2 + >> include/linux/stats_fs.h | 304 +++++++++ >> include/uapi/linux/magic.h | 1 + >> lib/refcount.c | 32 + >> tools/lib/api/fs/fs.c | 21 + >> virt/kvm/arm/arm.c | 2 +- >> virt/kvm/kvm_main.c | 314 ++------- >> 32 files changed, 2772 insertions(+), 382 deletions(-) >> delete mode 100644 arch/x86/kvm/debugfs.c >> create mode 100644 arch/x86/kvm/stats_fs.c >> create mode 100644 fs/stats_fs/Makefile >> create mode 100644 fs/stats_fs/inode.c >> create mode 100644 fs/stats_fs/internal.h >> create mode 100644 fs/stats_fs/stats_fs-tests.c >> create mode 100644 fs/stats_fs/stats_fs.c >> create mode 100644 include/linux/stats_fs.h >> >> -- >> 2.25.2 >>