From 6555acdefc758a4dae7038c3f2301f311e287218 Mon Sep 17 00:00:00 2001 From: Mordechay Goodstein Date: Tue, 2 Jul 2024 19:21:18 +0200 Subject: um: time-travel: support time-travel protocol broadcast messages Add a message type to the time-travel protocol to broadcast a small (64-bit) value to all participants in a simulation. The main use case is to have an identical message come to all participants in a simulation, e.g. to separate out logs for different tests running in a single simulation. Down in the guts of time_travel_handle_message() we can't use printk() and not even printk_deferred(), so just store the message and print it at the start of the userspace() function. Unfortunately this means that other prints in the kernel can actually bypass the message, but in most cases where this is used, for example to separate test logs, userspace will be involved. Also, even if we could use printk_deferred(), we'd still need to flush it out in the userspace() function since otherwise userspace messages might cross it. As a result, this is a reasonable compromise, there's no need to have any core changes and it solves the main use case we have for it. Signed-off-by: Mordechay Goodstein Link: https://patch.msgid.link/20240702192118.c4093bc5b15e.I2ca8d006b67feeb866ac2017af7b741c9e06445a@changeid Signed-off-by: Johannes Berg --- include/uapi/linux/um_timetravel.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'include/uapi') diff --git a/include/uapi/linux/um_timetravel.h b/include/uapi/linux/um_timetravel.h index ca3238222b6d..078ea401aa2a 100644 --- a/include/uapi/linux/um_timetravel.h +++ b/include/uapi/linux/um_timetravel.h @@ -123,6 +123,17 @@ enum um_timetravel_ops { * the simulation. */ UM_TIMETRAVEL_GET_TOD = 8, + + /** + * @UM_TIMETRAVEL_BROADCAST: Send/Receive a broadcast message. + * This message can be used to sync all components in the system + * with a single message, if the calender gets the message, the + * calender broadcast the message to all components, and if a + * component receives it it should act based on it e.g print a + * message to it's log system. + * (calendar <-> host) + */ + UM_TIMETRAVEL_BROADCAST = 9, }; #endif /* _UAPI_LINUX_UM_TIMETRAVEL_H */ -- cgit v1.2.3 From bfb80d8bc92fa70f5b44a57ed2b24d57685fe188 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Tue, 2 Jul 2024 19:21:21 +0200 Subject: um: add shared memory optimisation for time-travel=ext With external time travel, a LOT of message can end up being exchanged on the socket, taking a significant amount of time just to do that. Add a new shared memory optimisation to that, where a number of changes are made: - the controller sends a client ID and a shared memory FD (and a logging FD we don't use) in the ACK message to the initial START - the shared memory holds the current time and the free_until value, so that there's no need to exchange messages for that - if the client that's running has shared memory support, any client (the running one included) can request the next time it wants to run inside the shared memory, rather than sending a message, by also updating the free_until value - when shared memory is enabled, RUN/WAIT messages no longer have an ACK, further cutting down on messages Together, this can reduce the number of messages very significantly, and reduce overall test/simulation run time. Co-developed-by: Mordechay Goodstein Signed-off-by: Mordechay Goodstein Link: https://patch.msgid.link/20240702192118.6ad0a083f574.Ie41206c8ce4507fe26b991937f47e86c24ca7a31@changeid Signed-off-by: Johannes Berg --- include/uapi/linux/um_timetravel.h | 179 ++++++++++++++++++++++++++++++++++--- 1 file changed, 165 insertions(+), 14 deletions(-) (limited to 'include/uapi') diff --git a/include/uapi/linux/um_timetravel.h b/include/uapi/linux/um_timetravel.h index 078ea401aa2a..546a690b0346 100644 --- a/include/uapi/linux/um_timetravel.h +++ b/include/uapi/linux/um_timetravel.h @@ -1,17 +1,6 @@ +/* SPDX-License-Identifier: BSD-3-Clause */ /* - * Permission to use, copy, modify, and/or distribute this software for any - * purpose with or without fee is hereby granted, provided that the above - * copyright notice and this permission notice appear in all copies. - * - * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES - * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF - * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR - * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES - * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN - * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF - * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. - * - * Copyright (C) 2019 Intel Corporation + * Copyright (C) 2019 - 2023 Intel Corporation */ #ifndef _UAPI_LINUX_UM_TIMETRAVEL_H #define _UAPI_LINUX_UM_TIMETRAVEL_H @@ -50,6 +39,36 @@ struct um_timetravel_msg { __u64 time; }; +/* max number of file descriptors that can be sent/received in a message */ +#define UM_TIMETRAVEL_MAX_FDS 2 + +/** + * enum um_timetravel_shared_mem_fds - fds sent in ACK message for START message + */ +enum um_timetravel_shared_mem_fds { + /** + * @UM_TIMETRAVEL_SHARED_MEMFD: Index of the shared memory file + * descriptor in the control message + */ + UM_TIMETRAVEL_SHARED_MEMFD, + /** + * @UM_TIMETRAVEL_SHARED_LOGFD: Index of the logging file descriptor + * in the control message + */ + UM_TIMETRAVEL_SHARED_LOGFD, + UM_TIMETRAVEL_SHARED_MAX_FDS, +}; + +/** + * enum um_timetravel_start_ack - ack-time mask for start message + */ +enum um_timetravel_start_ack { + /** + * @UM_TIMETRAVEL_START_ACK_ID: client ID that controller allocated. + */ + UM_TIMETRAVEL_START_ACK_ID = 0xffff, +}; + /** * enum um_timetravel_ops - Operation codes */ @@ -57,7 +76,9 @@ enum um_timetravel_ops { /** * @UM_TIMETRAVEL_ACK: response (ACK) to any previous message, * this usually doesn't carry any data in the 'time' field - * unless otherwise specified below + * unless otherwise specified below, note: while using shared + * memory no ACK for WAIT and RUN messages, for more info see + * &struct um_timetravel_schedshm. */ UM_TIMETRAVEL_ACK = 0, @@ -136,4 +157,134 @@ enum um_timetravel_ops { UM_TIMETRAVEL_BROADCAST = 9, }; +/* version of struct um_timetravel_schedshm */ +#define UM_TIMETRAVEL_SCHEDSHM_VERSION 2 + +/** + * enum um_timetravel_schedshm_cap - time travel capabilities of every client + * + * These flags must be set immediately after processing the ACK to + * the START message, before sending any message to the controller. + */ +enum um_timetravel_schedshm_cap { + /** + * @UM_TIMETRAVEL_SCHEDSHM_CAP_TIME_SHARE: client can read current time + * update internal time request to shared memory and read + * free until and send no Ack on RUN and doesn't expect ACK on + * WAIT. + */ + UM_TIMETRAVEL_SCHEDSHM_CAP_TIME_SHARE = 0x1, +}; + +/** + * enum um_timetravel_schedshm_flags - time travel flags of every client + */ +enum um_timetravel_schedshm_flags { + /** + * @UM_TIMETRAVEL_SCHEDSHM_FLAGS_REQ_RUN: client has a request to run. + * It's set by client when it has a request to run, if (and only + * if) the @running_id points to a client that is able to use + * shared memory, i.e. has %UM_TIMETRAVEL_SCHEDSHM_CAP_TIME_SHARE + * (this includes the client itself). Otherwise, a message must + * be used. + */ + UM_TIMETRAVEL_SCHEDSHM_FLAGS_REQ_RUN = 0x1, +}; + +/** + * DOC: Time travel shared memory overview + * + * The main purpose of the shared memory is to avoid all time travel message + * that don't need any action, for example current time can be held in shared + * memory without the need of any client to send a message UM_TIMETRAVEL_GET + * in order to know what's the time. + * + * Since this is shared memory with all clients and controller and controller + * creates the shared memory space, all time values are absolute to controller + * time. So first time client connects to shared memory mode it should take the + * current_time value in shared memory and keep it internally as a diff to + * shared memory times, and once shared memory is initialized, any interaction + * with the controller must happen in the controller time domain, including any + * messages (for clients that are not using shared memory, the controller will + * handle an offset and make the clients think they start at time zero.) + * + * Along with the shared memory file descriptor is sent to the client a logging + * file descriptor, to have all logs related to shared memory, + * logged into one place. note: to have all logs synced into log file at write, + * file should be flushed (fflush) after writing to it. + * + * To avoid memory corruption, we define below for each field who can write to + * it at what time, defined in the structure fields. + * + * To avoid having to pack this struct, all fields in it must be naturally aligned + * (i.e. aligned to their size). + */ + +/** + * union um_timetravel_schedshm_client - UM time travel client struct + * + * Every entity using the shared memory including the controller has a place in + * the um_timetravel_schedshm clients array, that holds info related to the client + * using the shared memory, and can be set only by the client after it gets the + * fd memory. + * + * @capa: bit fields with client capabilities see + * &enum um_timetravel_schedshm_cap, set by client once after getting the + * shared memory file descriptor. + * @flags: bit fields for flags see &enum um_timetravel_schedshm_flags for doc. + * @req_time: request time to run, set by client on every request it needs. + * @name: unique id sent to the controller by client with START message. + */ +union um_timetravel_schedshm_client { + struct { + __u32 capa; + __u32 flags; + __u64 req_time; + __u64 name; + }; + char reserve[128]; /* reserved for future usage */ +}; + +/** + * struct um_timetravel_schedshm - UM time travel shared memory struct + * + * @hdr: header fields: + * @version: Current version struct UM_TIMETRAVEL_SCHEDSHM_VERSION, + * set by controller once at init, clients must check this after mapping + * and work without shared memory if they cannot handle the indicated + * version. + * @len: Length of all the memory including header (@hdr), clients should once + * per connection first mmap the header and take the length (@len) to remap the entire size. + * This is done in order to support dynamic struct size letting number of + * clients be dynamic based on controller support. + * @free_until: Stores the next request to run by any client, in order for the + * current client to know how long it can still run. A client needs to (at + * least) reload this value immediately after communicating with any other + * client, since the controller will update this field when a new request + * is made by any client. Clients also must update this value when they + * insert/update an own request into the shared memory while not running + * themselves, and the new request is before than the current value. + * current_time: Current time, can only be set by the client in running state + * (indicated by @running_id), though that client may only run until @free_until, + * so it must remain smaller than @free_until. + * @running_id: The current client in state running, set before a client is + * notified that it's now running. + * @max_clients: size of @clients array, set once at init by the controller. + * @clients: clients array see &union um_timetravel_schedshm_client for doc, + * set only by client. + */ +struct um_timetravel_schedshm { + union { + struct { + __u32 version; + __u32 len; + __u64 free_until; + __u64 current_time; + __u16 running_id; + __u16 max_clients; + }; + char hdr[4096]; /* align to 4K page size */ + }; + union um_timetravel_schedshm_client clients[]; +}; #endif /* _UAPI_LINUX_UM_TIMETRAVEL_H */ -- cgit v1.2.3