From patchwork Fri Mar 17 14:33:08 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13179117 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB7E7C6FD1D for ; Fri, 17 Mar 2023 14:33:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229962AbjCQOdf (ORCPT ); Fri, 17 Mar 2023 10:33:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229697AbjCQOdf (ORCPT ); Fri, 17 Mar 2023 10:33:35 -0400 Received: from mail-wm1-x349.google.com (mail-wm1-x349.google.com [IPv6:2a00:1450:4864:20::349]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF62B1F497 for ; Fri, 17 Mar 2023 07:33:28 -0700 (PDT) Received: by mail-wm1-x349.google.com with SMTP id 1-20020a05600c024100b003ec8023ac4eso1978761wmj.0 for ; Fri, 17 Mar 2023 07:33:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1679063607; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=NAlu1ZsRN3U938dPa2PYC4fE3ZHRDQI3wHPzWFpTsMc=; b=NJvWR0UNYLX65E1V3A7V+zzgtw/7Cckr9NZqdavukoK9+16y+Q4B8CXE5d3hZ+8nhK JQzJLFsdkJbsbYxO3wXkYhlMgfR6/a0kyp0Blg6RkVPxKHZ15vULo7LU+1MO478YrZyc rFOsBzHKPj+skT3PxZMXVUYzl3aUQ1Liz/XYMyQ70/ercjSFktl73TEP7+I18PUhwUJe f9FXNb+sqFDlb8/AS44gTPEof8PfXmtgIUTKMiQW2xMTngOJ+niXauFEwqBVsRFec4TL f9AP9AEGDbTeNOvsbO9kVe1oGpPU+SF6r3jC47pH00Yv4OuqMgGg/zmnV0nmXCRCv9AP JZqg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679063607; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=NAlu1ZsRN3U938dPa2PYC4fE3ZHRDQI3wHPzWFpTsMc=; b=6x0KEBgCnTf2f1zX5EWRn6RwFMF5aYxCocSythCEPUAaMKxS+zMIbxmeBY8nJo6PEz HyGsa191DjAFtICgzNvkCRXtE20ar2HA9r8FCF8CuYGQI/lNn3LNUs2/vyvi2qaZGnrD TnMvOsbrq0I2TPqFYTO8tpsaLuDrVoszvU6Zi5vSxrKqEk5zcX+kjFouLn3EPADqVnit tSB1/U9ZTfbeFi02eP0Gfv80Su4mrH6GFx0EhEv9bQANVchhol6DsEnZWoiJY4DMpoTg bGbCzfKvRx725Kv7szpQqv9cfp19Jd8Up9gcAevaDClVgRBUQHzYDmh9d3LWVwwaMmbr JBNw== X-Gm-Message-State: AO0yUKXKjk/4NwAucoMu2XulaAELXAdTzkPG5IgcnXao+trkyXONw93D +CYhQ9MB2rNAkn0JH2aGX5HeJoMf9TkSE9ng X-Google-Smtp-Source: AK7set+7i4rX5HlPHHRPyI7UrjRAR/rq3GDVZ5hV79/j+cfQxDj/ZYO0b1RyevsjLgoELhJey2bLx5gehlSuNH7O X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a5d:64ec:0:b0:2c7:e48:8c98 with SMTP id g12-20020a5d64ec000000b002c70e488c98mr961410wri.4.1679063607189; Fri, 17 Mar 2023 07:33:27 -0700 (PDT) Date: Fri, 17 Mar 2023 14:33:08 +0000 Mime-Version: 1.0 X-Mailer: git-send-email 2.40.0.rc1.284.g88254d51c5-goog Message-ID: <20230317143310.1604700-1-vdonnefort@google.com> Subject: [PATCH 0/2] Introducing trace buffer mapping by user-space From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: kernel-team@android.com, Vincent Donnefort Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org The tracing ring-buffers can be stored on disk or sent to network without any copy via splice. However the later doesn't allow real time processing of the traces. A solution is to give access to userspace to the ring-buffer pages directly via a mapping. A piece of software can now become a reader of the ring-buffer, and drive a consuming or non-consuming read in a similar fashion to what trace and trace_pipe offer. Attached to this cover letter an example of consuming read for a ring-buffer, using libtracefs. Vincent --- #include #include #include #include #include #include #include #include #include #include #include #include #include #define TRACE_MMAP_IOCTL_GET_READER_PAGE _IO('T', 0x1) struct ring_buffer_meta_page { __u64 entries; __u64 overrun; __u32 pages_touched; __u32 reader_page; __u32 nr_data_pages; __u32 data_page_head; __u32 data_pages[]; }; /* Need to access private struct to save counters */ struct kbuffer { unsigned long long timestamp; long long lost_events; unsigned long flags; void *subbuffer; void *data; unsigned int index; unsigned int curr; unsigned int next; unsigned int size; unsigned int start; unsigned int first; unsigned int (*read_4)(void *ptr); unsigned long long (*read_8)(void *ptr); unsigned long long (*read_long)(struct kbuffer *kbuf, void *ptr); int (*next_event)(struct kbuffer *kbuf); }; static char *argv0; static bool need_exit; static char *get_this_name(void) { static char *this_name; char *arg; char *p; if (this_name) return this_name; arg = argv0; p = arg+strlen(arg); while (p >= arg && *p != '/') p--; p++; this_name = p; return p; } static void __vdie(const char *fmt, va_list ap, int err) { int ret = errno; char *p = get_this_name(); if (err && errno) perror(p); else ret = -1; fprintf(stderr, " "); vfprintf(stderr, fmt, ap); fprintf(stderr, "\n"); exit(ret); } void pdie(const char *fmt, ...) { va_list ap; va_start(ap, fmt); __vdie(fmt, ap, 1); va_end(ap); } static void read_page(struct tep_handle *tep, struct kbuffer *kbuf, void *data, int page) { static struct trace_seq seq; struct tep_record record; if (seq.buffer) trace_seq_reset(&seq); else trace_seq_init(&seq); while ((record.data = kbuffer_read_event(kbuf, &record.ts))) { kbuffer_next_event(kbuf, NULL); tep_print_event(tep, &seq, &record, "%s-%d %9d\t%s\n", TEP_PRINT_COMM, TEP_PRINT_PID, TEP_PRINT_TIME, TEP_PRINT_NAME); trace_seq_do_printf(&seq); trace_seq_reset(&seq); } } static int next_reader_page(int fd, struct ring_buffer_meta_page *meta, struct kbuffer *kbuf) { int prev_reader_page = meta->reader_page; if (ioctl(fd, TRACE_MMAP_IOCTL_GET_READER_PAGE) < 0) pdie("ioctl"); return meta->reader_page; } static void signal_handler(int unused) { printf("Exit!\n"); need_exit = true; } int main(int argc, char **argv) { int page_size, data_len, page, fd, start = -1; struct ring_buffer_meta_page *map; struct kbuffer *kbuf, prev_kbuf; struct tep_handle *tep; __u64 prev_entries; void *meta, *data; char *buf, path[32]; int cpu; argv0 = argv[0]; cpu = atoi(argv[1]); snprintf(path, 32, "per_cpu/cpu%d/trace_pipe_raw", cpu); tep = tracefs_local_events(NULL); kbuf = tep_kbuffer(tep); page_size = getpagesize(); fd = tracefs_instance_file_open(NULL, path, O_RDONLY); if (fd < 0) pdie("raw"); meta = mmap(NULL, page_size, PROT_READ, MAP_SHARED, fd, 0); if (meta == MAP_FAILED) pdie("mmap"); map = meta; printf("entries: %llu\n", map->entries); printf("overrun: %llu\n", map->overrun); printf("pages_touched: %u\n", map->pages_touched); printf("reader_page: %u\n", map->reader_page); printf("nr_data_pages: %u\n\n", map->nr_data_pages); data_len = page_size * (map->nr_data_pages + 1); data = mmap(NULL, data_len, PROT_READ, MAP_SHARED, fd, page_size); if (data == MAP_FAILED) pdie("mmap data"); signal(SIGINT, signal_handler); page = ((struct ring_buffer_meta_page*)meta)->reader_page; again: do { kbuffer_load_subbuffer(kbuf, data + page_size * page); if (page != start) { printf("READER PAGE: %d\n", map->reader_page); } else { kbuf->curr = prev_kbuf.curr; kbuf->index = prev_kbuf.index; kbuf->next = prev_kbuf.next; kbuf->timestamp = prev_kbuf.timestamp; kbuffer_next_event(kbuf, NULL); } prev_entries = map->entries; start = page; read_page(tep, kbuf, data, page); } while ((page = next_reader_page(fd, meta, kbuf)) != start); prev_kbuf.curr = kbuf->curr; prev_kbuf.index = kbuf->index; prev_kbuf.next = kbuf->next; prev_kbuf.timestamp = kbuf->timestamp; while (prev_entries == *(volatile __u64 *)&map->entries && !need_exit) usleep(100000); if (!need_exit) goto again; munmap(data, data_len); munmap(meta, page_size); close(fd); return 0; } Vincent Donnefort (2): ring-buffer: Introducing ring-buffer mapping functions tracing: Allow user-space mapping of the ring-buffer include/linux/ring_buffer.h | 8 + include/uapi/linux/trace_mmap.h | 27 +++ kernel/trace/ring_buffer.c | 334 +++++++++++++++++++++++++++++++- kernel/trace/trace.c | 73 ++++++- 4 files changed, 436 insertions(+), 6 deletions(-) create mode 100644 include/uapi/linux/trace_mmap.h