| Message ID | 1606146274-246154-3-git-send-email-andrey.shinkevich@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Increase amount of data for monitor to read | expand |
23.11.2020 18:44, Andrey Shinkevich wrote: > QMP and HMP monitors read one byte at a time from the socket or stdin, > which is very inefficient. With 100+ VMs on the host, this results in > multiple extra system calls and CPU overuse. > This patch increases the amount of read data up to 4096 bytes that fits > the buffer size on the channel level. > A JSON little parser is introduced to throttle QMP commands read from > the buffer so that incoming requests do not overflow the monitor input > queue. > > Suggested-by: Denis V. Lunev<den@openvz.org> > Signed-off-by: Andrey Shinkevich<andrey.shinkevich@virtuozzo.com> Can't we just increase qmp queue instead? It seems a lot simpler: diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h index 348bfad3d5..7e721eee3f 100644 --- a/include/monitor/monitor.h +++ b/include/monitor/monitor.h @@ -8,7 +8,7 @@ typedef struct MonitorHMP MonitorHMP; typedef struct MonitorOptions MonitorOptions; -#define QMP_REQ_QUEUE_LEN_MAX 8 +#define QMP_REQ_QUEUE_LEN_MAX 4096 extern QemuOptsList qemu_mon_opts; diff --git a/monitor/monitor.c b/monitor/monitor.c index 84222cd130..1588f00306 100644 --- a/monitor/monitor.c +++ b/monitor/monitor.c @@ -566,7 +566,7 @@ int monitor_can_read(void *opaque) { Monitor *mon = opaque; - return !qatomic_mb_read(&mon->suspend_cnt); + return !qatomic_mb_read(&mon->suspend_cnt) ? 4096 : 0; } - with this patch tests pass and performance is even better.
24.11.2020 14:03, Vladimir Sementsov-Ogievskiy wrote: > 23.11.2020 18:44, Andrey Shinkevich wrote: >> QMP and HMP monitors read one byte at a time from the socket or stdin, >> which is very inefficient. With 100+ VMs on the host, this results in >> multiple extra system calls and CPU overuse. >> This patch increases the amount of read data up to 4096 bytes that fits >> the buffer size on the channel level. >> A JSON little parser is introduced to throttle QMP commands read from >> the buffer so that incoming requests do not overflow the monitor input >> queue. >> >> Suggested-by: Denis V. Lunev<den@openvz.org> >> Signed-off-by: Andrey Shinkevich<andrey.shinkevich@virtuozzo.com> > > > Can't we just increase qmp queue instead? It seems a lot simpler: > > diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h > index 348bfad3d5..7e721eee3f 100644 > --- a/include/monitor/monitor.h > +++ b/include/monitor/monitor.h > @@ -8,7 +8,7 @@ > typedef struct MonitorHMP MonitorHMP; > typedef struct MonitorOptions MonitorOptions; > > -#define QMP_REQ_QUEUE_LEN_MAX 8 > +#define QMP_REQ_QUEUE_LEN_MAX 4096 > > extern QemuOptsList qemu_mon_opts; > > diff --git a/monitor/monitor.c b/monitor/monitor.c > index 84222cd130..1588f00306 100644 > --- a/monitor/monitor.c > +++ b/monitor/monitor.c > @@ -566,7 +566,7 @@ int monitor_can_read(void *opaque) > { > Monitor *mon = opaque; > > - return !qatomic_mb_read(&mon->suspend_cnt); > + return !qatomic_mb_read(&mon->suspend_cnt) ? 4096 : 0; > } > > > - with this patch tests pass and performance is even better. > > Suddenly I found, that this patch ^^ was sent a year ago: https://patchew.org/QEMU/20190610105906.28524-1-dplotnikov@virtuozzo.com/ some questions were asked, so I think we should start from it.
On 24.11.2020 14:03, Vladimir Sementsov-Ogievskiy wrote: > 23.11.2020 18:44, Andrey Shinkevich wrote: >> QMP and HMP monitors read one byte at a time from the socket or stdin, >> which is very inefficient. With 100+ VMs on the host, this results in >> multiple extra system calls and CPU overuse. >> This patch increases the amount of read data up to 4096 bytes that fits >> the buffer size on the channel level. >> A JSON little parser is introduced to throttle QMP commands read from >> the buffer so that incoming requests do not overflow the monitor input >> queue. >> >> Suggested-by: Denis V. Lunev<den@openvz.org> >> Signed-off-by: Andrey Shinkevich<andrey.shinkevich@virtuozzo.com> > > > Can't we just increase qmp queue instead? It seems a lot simpler: > With the OOB compatibility disabled, the monitor queues one QMP command at most. It was made for the backward compatibility as stated in the comment before pushing a command into the queue. To keep that concept functional, the monitor should track the end of a single QMP command. It allows the dispatcher handling the command and send a response to client in time. With the patch below, the monitor queue will be filled with QMP commands as many as they will be found in the input buffer. The first command execution {"execute":"qmp_capabilities"} takes more time and queue will be filled at full. Then the dispatcher starts execution of other commands in the monitor queue. The process becomes synchronious. In this case, we need neither thread nor the queue. Andrey > diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h > index 348bfad3d5..7e721eee3f 100644 > --- a/include/monitor/monitor.h > +++ b/include/monitor/monitor.h > @@ -8,7 +8,7 @@ > typedef struct MonitorHMP MonitorHMP; > typedef struct MonitorOptions MonitorOptions; > > -#define QMP_REQ_QUEUE_LEN_MAX 8 > +#define QMP_REQ_QUEUE_LEN_MAX 4096 > > extern QemuOptsList qemu_mon_opts; > > diff --git a/monitor/monitor.c b/monitor/monitor.c > index 84222cd130..1588f00306 100644 > --- a/monitor/monitor.c > +++ b/monitor/monitor.c > @@ -566,7 +566,7 @@ int monitor_can_read(void *opaque) > { > Monitor *mon = opaque; > > - return !qatomic_mb_read(&mon->suspend_cnt); > + return !qatomic_mb_read(&mon->suspend_cnt) ? 4096 : 0; > } > > > - with this patch tests pass and performance is even better. > >
diff --git a/chardev/char-fd.c b/chardev/char-fd.c index 1cd62f2..15bc8f4 100644 --- a/chardev/char-fd.c +++ b/chardev/char-fd.c @@ -33,6 +33,8 @@ #include "chardev/char-fd.h" #include "chardev/char-io.h" +#include "monitor/monitor-internal.h" + /* Called with chr_write_lock held. */ static int fd_chr_write(Chardev *chr, const uint8_t *buf, int len) { @@ -45,8 +47,12 @@ static gboolean fd_chr_read(QIOChannel *chan, GIOCondition cond, void *opaque) { Chardev *chr = CHARDEV(opaque); FDChardev *s = FD_CHARDEV(opaque); + CharBackend *be = chr->be; + Monitor *mon = (Monitor *)be->opaque; int len; uint8_t buf[CHR_READ_BUF_LEN]; + uint8_t *cursor; + int load, size, pos; ssize_t ret; len = sizeof(buf); @@ -62,10 +68,35 @@ static gboolean fd_chr_read(QIOChannel *chan, GIOCondition cond, void *opaque) if (ret == 0) { remove_fd_in_watch(chr); qemu_chr_be_event(chr, CHR_EVENT_CLOSED); + chr->json_thl = (const JSONthrottle){0}; return FALSE; } - if (ret > 0) { - qemu_chr_be_write(chr, buf, ret); + if (ret < 0) { + return TRUE; + } + load = ret; + cursor = buf; + + while (load > 0) { + size = load; + if (monitor_is_qmp(mon)) { + /* Find the end position of a JSON command in the input buffer */ + pos = qemu_chr_end_position((const char *) cursor, size, + &chr->json_thl); + if (pos >= 0) { + size = pos + 1; + } + } + + qemu_chr_be_write(chr, cursor, size); + cursor += size; + load -= size; + + if (load > 0) { + while (qatomic_mb_read(&mon->suspend_cnt)) { + g_usleep(40); + } + } } return TRUE; diff --git a/chardev/char-socket.c b/chardev/char-socket.c index 213a4c8..30ad1d4 100644 --- a/chardev/char-socket.c +++ b/chardev/char-socket.c @@ -38,6 +38,8 @@ #include "chardev/char-io.h" #include "qom/object.h" +#include "monitor/monitor-internal.h" + /***********************************************************/ /* TCP Net console */ @@ -522,7 +524,11 @@ static gboolean tcp_chr_read(QIOChannel *chan, GIOCondition cond, void *opaque) { Chardev *chr = CHARDEV(opaque); SocketChardev *s = SOCKET_CHARDEV(opaque); + CharBackend *be = chr->be; + Monitor *mon = (Monitor *)be->opaque; uint8_t buf[CHR_READ_BUF_LEN]; + uint8_t *cursor; + int load, pos; int len, size; if ((s->state != TCP_CHARDEV_STATE_CONNECTED) || @@ -537,12 +543,42 @@ static gboolean tcp_chr_read(QIOChannel *chan, GIOCondition cond, void *opaque) if (size == 0 || (size == -1 && errno != EAGAIN)) { /* connection closed */ tcp_chr_disconnect(chr); - } else if (size > 0) { + chr->json_thl = (const JSONthrottle){0}; + return TRUE; + } + if (size < 0) { + return TRUE; + } + load = size; + cursor = buf; + + while (load > 0) { + size = load; + if (monitor_is_qmp(mon)) { + /* Find the end position of a JSON command in the input buffer */ + pos = qemu_chr_end_position((const char *) cursor, size, + &chr->json_thl); + if (pos >= 0) { + size = pos + 1; + } + } + len = size; + if (s->do_telnetopt) { - tcp_chr_process_IAC_bytes(chr, s, buf, &size); + tcp_chr_process_IAC_bytes(chr, s, cursor, &size); } if (size > 0) { - qemu_chr_be_write(chr, buf, size); + qemu_chr_be_write(chr, cursor, size); + cursor += size; + load -= size; + } else { + cursor += len; + load -= len; + } + if (load > 0) { + while (qatomic_mb_read(&mon->suspend_cnt)) { + g_usleep(40); + } } } diff --git a/chardev/char.c b/chardev/char.c index aa42821..75c7bc7 100644 --- a/chardev/char.c +++ b/chardev/char.c @@ -1178,6 +1178,47 @@ GSource *qemu_chr_timeout_add_ms(Chardev *chr, guint ms, return source; } +/* + * Split up the incoming buffered stream into separate QMP commands so that the + * QMP monitor queue is not overflown with requests. The function looks for + * the last paired brace/bracket in a JSON format text. It is a simplified + * parser implemented in the json_message_process_token() function. + */ +int qemu_chr_end_position(const char *buf, int size, JSONthrottle *thl) +{ + int i; + + for (i = 0; i < size; i++) { + switch (buf[i]) { + case ' ': + case '\n': + case '\r': + continue; + case '{': + thl->brace_count++; + break; + case '}': + thl->brace_count--; + break; + case '[': + thl->bracket_count++; + break; + case ']': + thl->bracket_count--; + break; + default: + break; + } + /* The same condition as it is in the json_message_process_token() */ + if ((thl->brace_count > 0 || thl->bracket_count > 0) + && thl->brace_count >= 0 && thl->bracket_count >= 0) { + continue; + } + return i; + } + return -1; +} + void qemu_chr_cleanup(void) { object_unparent(get_chardevs_root()); diff --git a/include/chardev/char.h b/include/chardev/char.h index db42f0a..6026293 100644 --- a/include/chardev/char.h +++ b/include/chardev/char.h @@ -16,6 +16,8 @@ /* character device */ typedef struct CharBackend CharBackend; +/* Throttler helper to separate QMP commands in JSON format text */ +typedef struct JSONthrottle JSONthrottle; typedef enum { CHR_EVENT_BREAK, /* serial break char */ @@ -56,6 +58,11 @@ typedef enum { #define qemu_chr_replay(chr) qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_REPLAY) +struct JSONthrottle { + int brace_count; + int bracket_count; +}; + struct Chardev { Object parent_obj; @@ -65,6 +72,7 @@ struct Chardev { char *filename; int logfd; int be_open; + JSONthrottle json_thl; GSource *gsource; GMainContext *gcontext; DECLARE_BITMAP(features, QEMU_CHAR_FEATURE_LAST); @@ -141,6 +149,13 @@ Chardev *qemu_chr_new_mux_mon(const char *label, const char *filename, void qemu_chr_change(QemuOpts *opts, Error **errp); /** + * Split the incoming buffered stream so that the QMP monitor queue is not + * overflown with requests. The function looks for the last paired + * brace/bracket in a JSON command. + */ +int qemu_chr_end_position(const char *buf, int size, JSONthrottle *thl); + +/** * qemu_chr_cleanup: * * Delete all chardevs (when leaving qemu) diff --git a/monitor/monitor.c b/monitor/monitor.c index 84222cd..43d2d3b 100644 --- a/monitor/monitor.c +++ b/monitor/monitor.c @@ -566,7 +566,7 @@ int monitor_can_read(void *opaque) { Monitor *mon = opaque; - return !qatomic_mb_read(&mon->suspend_cnt); + return !qatomic_mb_read(&mon->suspend_cnt) ? CHR_READ_BUF_LEN : 0; } void monitor_list_append(Monitor *mon)
QMP and HMP monitors read one byte at a time from the socket or stdin, which is very inefficient. With 100+ VMs on the host, this results in multiple extra system calls and CPU overuse. This patch increases the amount of read data up to 4096 bytes that fits the buffer size on the channel level. A JSON little parser is introduced to throttle QMP commands read from the buffer so that incoming requests do not overflow the monitor input queue. Suggested-by: Denis V. Lunev <den@openvz.org> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> --- chardev/char-fd.c | 35 +++++++++++++++++++++++++++++++++-- chardev/char-socket.c | 42 +++++++++++++++++++++++++++++++++++++++--- chardev/char.c | 41 +++++++++++++++++++++++++++++++++++++++++ include/chardev/char.h | 15 +++++++++++++++ monitor/monitor.c | 2 +- 5 files changed, 129 insertions(+), 6 deletions(-)