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Mon, 14 Aug 2023 09:32:02 -0700 (PDT) From: Nicholas Piggin To: Pavel Dovgalyuk Cc: Nicholas Piggin , Paolo Bonzini , John Snow , Cleber Rosa , =?utf-8?q?Phi?= =?utf-8?q?lippe_Mathieu-Daud=C3=A9?= , Wainer dos Santos Moschetta , Beraldo Leal , qemu-devel@nongnu.org Subject: [PATCH 4/4] replay: simple auto-snapshot mode for record Date: Tue, 15 Aug 2023 02:31:35 +1000 Message-Id: <20230814163135.187882-5-npiggin@gmail.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230814163135.187882-1-npiggin@gmail.com> References: <20230814163135.187882-1-npiggin@gmail.com> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::62c; envelope-from=npiggin@gmail.com; helo=mail-pl1-x62c.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org record makes an initial snapshot when the machine is created, to enable reverse-debugging. Often the issue being debugged appears near the end of the trace, so it is important for performance to keep snapshots close to the end. This implements a periodic snapshot mode that keeps a rolling set of recent snapshots. Arguably this should be done by the debugger or a program that talks to QMP, but for setting up simple scenarios and tests, it is convenient to have this feature. Signed-off-by: Nicholas Piggin --- docs/system/replay.rst | 5 ++++ include/sysemu/replay.h | 11 ++++++++ qemu-options.hx | 9 +++++-- replay/replay-snapshot.c | 57 ++++++++++++++++++++++++++++++++++++++++ replay/replay.c | 25 ++++++++++++++++++ softmmu/vl.c | 9 +++++++ 6 files changed, 114 insertions(+), 2 deletions(-) diff --git a/docs/system/replay.rst b/docs/system/replay.rst index 3105327423..bef9ea4171 100644 --- a/docs/system/replay.rst +++ b/docs/system/replay.rst @@ -156,6 +156,11 @@ for storing VM snapshots. Here is the example of the command line for this: ``empty.qcow2`` drive does not connected to any virtual block device and used for VM snapshots only. +``rrsnapmode`` can be used to select just an initial snapshot or periodic +snapshots, with ``rrsnapcount`` specifying the number of periodic snapshots +to maintain, and ``rrsnaptime`` the amount of run time in seconds between +periodic snapshots. + .. _network-label: Network devices diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h index 08aae5869f..a83e54afc6 100644 --- a/include/sysemu/replay.h +++ b/include/sysemu/replay.h @@ -45,6 +45,17 @@ typedef enum ReplayCheckpoint ReplayCheckpoint; typedef struct ReplayNetState ReplayNetState; +enum ReplaySnapshotMode { + REPLAY_SNAPSHOT_MODE_INITIAL, + REPLAY_SNAPSHOT_MODE_PERIODIC, +}; +typedef enum ReplaySnapshotMode ReplaySnapshotMode; + +extern ReplaySnapshotMode replay_snapshot_mode; + +extern uint64_t replay_snapshot_periodic_delay; +extern int replay_snapshot_periodic_nr_keep; + /* Name of the initial VM snapshot */ extern char *replay_snapshot; diff --git a/qemu-options.hx b/qemu-options.hx index 29b98c3d4c..0dce93eeab 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -4530,13 +4530,13 @@ SRST ERST DEF("icount", HAS_ARG, QEMU_OPTION_icount, \ - "-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=[,rrsnapshot=]]\n" \ + "-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=[,rrsnapshot=][,rrsnapmode=initial|periodic][,rrsnaptime=secs][,rrsnapcount=N]\n" \ " enable virtual instruction counter with 2^N clock ticks per\n" \ " instruction, enable aligning the host and virtual clocks\n" \ " or disable real time cpu sleeping, and optionally enable\n" \ " record-and-replay mode\n", QEMU_ARCH_ALL) SRST -``-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=filename[,rrsnapshot=snapshot]]`` +``-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=filename[,rrsnapshot=snapshot][,rrsnapmode=initial|periodic][,rrsnaptime=secs][,rrsnapcount=N]]`` Enable virtual instruction counter. The virtual cpu will execute one instruction every 2^N ns of virtual time. If ``auto`` is specified then the virtual cpu speed will be automatically adjusted to keep @@ -4578,6 +4578,11 @@ SRST name. In record mode, a new VM snapshot with the given name is created at the start of execution recording. In replay mode this option specifies the snapshot name used to load the initial VM state. + ``rrsnapmode=periodic`` will additionally cause a periodic snapshot to + be created after ``rrsnaptime=secs`` seconds of real runtime. The last + ``rrsnapcount=N`` periodic snapshots (not including the initial) will + be kept (0 for infinite). Periodic snapshots are useful to speed + reverse debugging operations near the end of the recorded trace. ERST DEF("watchdog-action", HAS_ARG, QEMU_OPTION_watchdog_action, \ diff --git a/replay/replay-snapshot.c b/replay/replay-snapshot.c index 10a7cf7992..38eac61c43 100644 --- a/replay/replay-snapshot.c +++ b/replay/replay-snapshot.c @@ -69,6 +69,53 @@ void replay_vmstate_register(void) vmstate_register(NULL, 0, &vmstate_replay, &replay_state); } +static QEMUTimer *replay_snapshot_timer; +static int replay_snapshot_count; + +static void replay_snapshot_timer_cb(void *opaque) +{ + Error *err = NULL; + char *name; + + if (!replay_can_snapshot()) { + /* Try again soon */ + timer_mod(replay_snapshot_timer, + qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + + replay_snapshot_periodic_delay / 10); + return; + } + + name = g_strdup_printf("%s-%d", replay_snapshot, replay_snapshot_count); + if (!save_snapshot(name, + true, NULL, false, NULL, &err)) { + error_report_err(err); + error_report("Could not create periodic snapshot " + "for icount record, disabling"); + g_free(name); + return; + } + g_free(name); + replay_snapshot_count++; + + if (replay_snapshot_periodic_nr_keep >= 1 && + replay_snapshot_count > replay_snapshot_periodic_nr_keep) { + int del_nr; + + del_nr = replay_snapshot_count - replay_snapshot_periodic_nr_keep - 1; + name = g_strdup_printf("%s-%d", replay_snapshot, del_nr); + if (!delete_snapshot(name, false, NULL, &err)) { + error_report_err(err); + error_report("Could not delete periodic snapshot " + "for icount record"); + } + g_free(name); + } + + timer_mod(replay_snapshot_timer, + qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + + replay_snapshot_periodic_delay); +} + void replay_vmstate_init(void) { Error *err = NULL; @@ -81,6 +128,16 @@ void replay_vmstate_init(void) error_report("Could not create snapshot for icount record"); exit(1); } + + if (replay_snapshot_mode == REPLAY_SNAPSHOT_MODE_PERIODIC) { + replay_snapshot_timer = timer_new_ms(QEMU_CLOCK_REALTIME, + replay_snapshot_timer_cb, + NULL); + timer_mod(replay_snapshot_timer, + qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + + replay_snapshot_periodic_delay); + } + } else if (replay_mode == REPLAY_MODE_PLAY) { if (!load_snapshot(replay_snapshot, NULL, false, NULL, &err)) { error_report_err(err); diff --git a/replay/replay.c b/replay/replay.c index e64f71209a..fa5930700d 100644 --- a/replay/replay.c +++ b/replay/replay.c @@ -29,6 +29,10 @@ ReplayMode replay_mode = REPLAY_MODE_NONE; char *replay_snapshot; +ReplaySnapshotMode replay_snapshot_mode; +uint64_t replay_snapshot_periodic_delay; +int replay_snapshot_periodic_nr_keep; + /* Name of replay file */ static char *replay_filename; ReplayState replay_state; @@ -313,6 +317,27 @@ void replay_configure(QemuOpts *opts) } replay_snapshot = g_strdup(qemu_opt_get(opts, "rrsnapshot")); + if (replay_snapshot && mode == REPLAY_MODE_RECORD) { + const char *snapmode; + + snapmode = qemu_opt_get(opts, "rrsnapmode"); + if (!snapmode || !strcmp(snapmode, "initial")) { + replay_snapshot_mode = REPLAY_SNAPSHOT_MODE_INITIAL; + } else if (!strcmp(snapmode, "periodic")) { + replay_snapshot_mode = REPLAY_SNAPSHOT_MODE_PERIODIC; + } else { + error_report("Invalid rrsnapmode option: %s", snapmode); + exit(1); + } + + /* Default 10 host seconds of machine runtime per snapshot. */ + replay_snapshot_periodic_delay = + qemu_opt_get_number(opts, "rrsnaptime", 10) * 1000; + + /* Default 2, to cover at least the last 10 host seconds of runtime. */ + replay_snapshot_periodic_nr_keep = + qemu_opt_get_number(opts, "rrsnapcount", 2); + } replay_vmstate_register(); replay_enable(fname, mode); diff --git a/softmmu/vl.c b/softmmu/vl.c index b0b96f67fa..e032eb45e8 100644 --- a/softmmu/vl.c +++ b/softmmu/vl.c @@ -446,6 +446,15 @@ static QemuOptsList qemu_icount_opts = { }, { .name = "rrsnapshot", .type = QEMU_OPT_STRING, + }, { + .name = "rrsnapmode", + .type = QEMU_OPT_STRING, + }, { + .name = "rrsnaptime", + .type = QEMU_OPT_NUMBER, + }, { + .name = "rrsnapcount", + .type = QEMU_OPT_NUMBER, }, { /* end of list */ } },