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Date: Fri, 18 Nov 2011 12:37:40 -0200
From: Arnaldo Carvalho de Melo <acme@...hat.com>
To: Jiri Olsa <jolsa@...hat.com>
Cc: a.p.zijlstra@...llo.nl, mingo@...e.hu, paulus@...ba.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] perf tool: Introducing perf_mmap object
Em Fri, Nov 18, 2011 at 02:46:43PM +0100, Jiri Olsa escreveu:
> +++ b/tools/perf/builtin-test.c
> @@ -476,6 +477,7 @@ static int test__basic_mmap(void)
> expected_nr_events[nsyscalls], i, j;
> struct perf_evsel *evsels[nsyscalls], *evsel;
> int sample_size = __perf_evsel__sample_size(attr.sample_type);
> + struct perf_mmap *md;
>
> for (i = 0; i < nsyscalls; ++i) {
> char name[64];
> @@ -551,7 +553,9 @@ static int test__basic_mmap(void)
> ++foo;
> }
>
> - while ((event = perf_evlist__mmap_read(evlist, 0)) != NULL) {
> + md = &evlist->mmap[0];
> +
> + while ((event = perf_mmap__read(md)) != NULL) {
> struct perf_sample sample;
>
> if (event->header.type != PERF_RECORD_SAMPLE) {
Please keep perf_evlist__mmap_read() as just a wrapper for the above
operation, that way you reduce the patch size by not touching the
functions that use perf_evlist__mmap_read().
Later, if we think this is the right thing to do, i.e. to open code it
like you're doing above, we can elliminate it, but I think its better to
keep it as perf_evlist__mmap_read(evlist, 0) as it uses just one line
instead of the 4 above :-)
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index 8e02027..032f70d 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -38,6 +38,7 @@
> #include "util/cpumap.h"
> #include "util/xyarray.h"
> #include "util/sort.h"
> +#include "util/mmap.h"
>
> #include "util/debug.h"
>
> @@ -804,14 +805,16 @@ static void perf_event__process_sample(const union perf_event *event,
> return;
> }
>
> -static void perf_session__mmap_read_idx(struct perf_session *self, int idx)
> +static void session_mmap_read(struct perf_session *self,
> + struct perf_mmap *md)
> {
> - struct perf_sample sample;
> - struct perf_evsel *evsel;
> union perf_event *event;
> - int ret;
>
> - while ((event = perf_evlist__mmap_read(top.evlist, idx)) != NULL) {
> + while ((event = perf_mmap__read(md)) != NULL) {
> + struct perf_sample sample;
> + struct perf_evsel *evsel;
> + int ret;
> +
Ditto, all the above is not needed, just keep perf_evlist__mmap_read()
> ret = perf_session__parse_sample(self, event, &sample);
> if (ret) {
> pr_err("Can't parse sample, err = %d\n", ret);
> @@ -835,8 +838,10 @@ static void perf_session__mmap_read(struct perf_session *self)
> {
> int i;
>
> - for (i = 0; i < top.evlist->nr_mmaps; i++)
> - perf_session__mmap_read_idx(self, i);
> + for (i = 0; i < top.evlist->nr_mmaps; i++) {
> + struct perf_mmap *md = &top.evlist->mmap[i];
> + session_mmap_read(self, md);
> + }
ditto
> }
>
> static void start_counters(struct perf_evlist *evlist)
> diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> index 914c895..d79efbb 100644
> --- a/tools/perf/perf.h
> +++ b/tools/perf/perf.h
> @@ -104,32 +104,6 @@ void get_term_dimensions(struct winsize *ws);
> #include "util/types.h"
> #include <stdbool.h>
>
> -struct perf_mmap {
> - void *base;
> - int mask;
> - unsigned int prev;
> -};
> -
> -static inline unsigned int perf_mmap__read_head(struct perf_mmap *mm)
> -{
> - struct perf_event_mmap_page *pc = mm->base;
> - int head = pc->data_head;
> - rmb();
> - return head;
> -}
> -
> -static inline void perf_mmap__write_tail(struct perf_mmap *md,
> - unsigned long tail)
> -{
> - struct perf_event_mmap_page *pc = md->base;
> -
> - /*
> - * ensure all reads are done before we write the tail out.
> - */
> - /* mb(); */
> - pc->data_tail = tail;
> -}
> -
Ok, the above just moved to tools/perf/util/mmap.c, I guess, reading
on...
> /*
> * prctl(PR_TASK_PERF_EVENTS_DISABLE) will (cheaply) disable all
> * counters in the current task.
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 0f715d0..2237833 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -12,6 +12,7 @@
> #include "evlist.h"
> #include "evsel.h"
> #include "util.h"
> +#include "mmap.h"
>
> #include <sys/mman.h>
>
> @@ -200,82 +201,14 @@ struct perf_evsel *perf_evlist__id2evsel(struct perf_evlist *evlist, u64 id)
> return NULL;
> }
>
> -union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
> -{
> - /* XXX Move this to perf.c, making it generally available */
> - unsigned int page_size = sysconf(_SC_PAGE_SIZE);
> - struct perf_mmap *md = &evlist->mmap[idx];
> - unsigned int head = perf_mmap__read_head(md);
> - unsigned int old = md->prev;
> - unsigned char *data = md->base + page_size;
> - union perf_event *event = NULL;
Just keep this as a simple wrapper to the functions moved to the
perf_mmap__ class
> -
> - if (evlist->overwrite) {
> - /*
> - * If we're further behind than half the buffer, there's a chance
> - * the writer will bite our tail and mess up the samples under us.
> - *
> - * If we somehow ended up ahead of the head, we got messed up.
> - *
> - * In either case, truncate and restart at head.
> - */
> - int diff = head - old;
> - if (diff > md->mask / 2 || diff < 0) {
> - fprintf(stderr, "WARNING: failed to keep up with mmap data.\n");
> -
> - /*
> - * head points to a known good entry, start there.
> - */
> - old = head;
> - }
> - }
> -
> - if (old != head) {
> - size_t size;
> -
> - event = (union perf_event *)&data[old & md->mask];
> - size = event->header.size;
> -
> - /*
> - * Event straddles the mmap boundary -- header should always
> - * be inside due to u64 alignment of output.
> - */
> - if ((old & md->mask) + size != ((old + size) & md->mask)) {
> - unsigned int offset = old;
> - unsigned int len = min(sizeof(*event), size), cpy;
> - void *dst = &evlist->event_copy;
> -
> - do {
> - cpy = min(md->mask + 1 - (offset & md->mask), len);
> - memcpy(dst, &data[offset & md->mask], cpy);
> - offset += cpy;
> - dst += cpy;
> - len -= cpy;
> - } while (len);
> -
> - event = &evlist->event_copy;
> - }
> -
> - old += size;
> - }
> -
> - md->prev = old;
> -
> - if (!evlist->overwrite)
> - perf_mmap__write_tail(md, old);
> -
> - return event;
> -}
> -
> void perf_evlist__munmap(struct perf_evlist *evlist)
> {
> int i;
>
> for (i = 0; i < evlist->nr_mmaps; i++) {
> - if (evlist->mmap[i].base != NULL) {
> - munmap(evlist->mmap[i].base, evlist->mmap_len);
> - evlist->mmap[i].base = NULL;
> - }
> + struct perf_mmap *m = &evlist->mmap[i];
> + if (m->base != NULL)
> + perf_mmap__close(m);
Wouldn't it be perf_mmap__munmap() ?
> }
>
> free(evlist->mmap);
> @@ -292,20 +225,18 @@ int perf_evlist__alloc_mmap(struct perf_evlist *evlist)
> }
>
> static int __perf_evlist__mmap(struct perf_evlist *evlist,
> - int idx, int prot, int mask, int fd)
> + int idx, int fd)
> {
> - evlist->mmap[idx].prev = 0;
> - evlist->mmap[idx].mask = mask;
> - evlist->mmap[idx].base = mmap(NULL, evlist->mmap_len, prot,
> - MAP_SHARED, fd, 0);
> - if (evlist->mmap[idx].base == MAP_FAILED)
> + struct perf_mmap *m = &evlist->mmap[idx];
> +
> + if (perf_mmap__open(m, fd, evlist->overwrite, evlist->pages))
And here perf_mmap__mmap or at least perf_mmap__map and the other
perf_mmap__unmap?
> return -1;
>
> perf_evlist__add_pollfd(evlist, fd);
> return 0;
> }
>
> -static int perf_evlist__mmap_per_cpu(struct perf_evlist *evlist, int prot, int mask)
> +static int perf_evlist__mmap_per_cpu(struct perf_evlist *evlist)
> {
> struct perf_evsel *evsel;
> int cpu, thread;
> @@ -320,7 +251,7 @@ static int perf_evlist__mmap_per_cpu(struct perf_evlist *evlist, int prot, int m
> if (output == -1) {
> output = fd;
> if (__perf_evlist__mmap(evlist, cpu,
> - prot, mask, output) < 0)
> + output) < 0)
> goto out_unmap;
> } else {
> if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT, output) != 0)
> @@ -334,15 +265,14 @@ static int perf_evlist__mmap_per_cpu(struct perf_evlist *evlist, int prot, int m
>
> out_unmap:
> for (cpu = 0; cpu < evlist->cpus->nr; cpu++) {
> - if (evlist->mmap[cpu].base != NULL) {
> - munmap(evlist->mmap[cpu].base, evlist->mmap_len);
> - evlist->mmap[cpu].base = NULL;
> - }
> + struct perf_mmap *m = &evlist->mmap[cpu];
> + if (m->base != NULL)
> + perf_mmap__close(m);
ditto
> }
> return -1;
> }
>
> -static int perf_evlist__mmap_per_thread(struct perf_evlist *evlist, int prot, int mask)
> +static int perf_evlist__mmap_per_thread(struct perf_evlist *evlist)
> {
> struct perf_evsel *evsel;
> int thread;
> @@ -356,7 +286,7 @@ static int perf_evlist__mmap_per_thread(struct perf_evlist *evlist, int prot, in
> if (output == -1) {
> output = fd;
> if (__perf_evlist__mmap(evlist, thread,
> - prot, mask, output) < 0)
> + output) < 0)
> goto out_unmap;
> } else {
> if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT, output) != 0)
> @@ -369,10 +299,9 @@ static int perf_evlist__mmap_per_thread(struct perf_evlist *evlist, int prot, in
>
> out_unmap:
> for (thread = 0; thread < evlist->threads->nr; thread++) {
> - if (evlist->mmap[thread].base != NULL) {
> - munmap(evlist->mmap[thread].base, evlist->mmap_len);
> - evlist->mmap[thread].base = NULL;
> - }
> + struct perf_mmap *m = &evlist->mmap[thread];
> + if (m->base != NULL)
> + perf_mmap__close(m);
> }
> return -1;
> }
> @@ -421,10 +350,8 @@ static int perf_evlist__init_ids(struct perf_evlist *evlist)
> */
> int perf_evlist__mmap(struct perf_evlist *evlist, int pages, bool overwrite)
> {
> - unsigned int page_size = sysconf(_SC_PAGE_SIZE);
> - int mask = pages * page_size - 1, ret;
> const struct cpu_map *cpus = evlist->cpus;
> - int prot = PROT_READ | (overwrite ? 0 : PROT_WRITE);
> + int ret;
>
> if (evlist->mmap == NULL && perf_evlist__alloc_mmap(evlist) < 0)
> return -ENOMEM;
> @@ -433,16 +360,16 @@ int perf_evlist__mmap(struct perf_evlist *evlist, int pages, bool overwrite)
> return -ENOMEM;
>
> evlist->overwrite = overwrite;
> - evlist->mmap_len = (pages + 1) * page_size;
> + evlist->pages = pages;
>
> ret = perf_evlist__init_ids(evlist);
> if (ret)
> return ret;
>
> if (cpus->map[0] == -1)
> - return perf_evlist__mmap_per_thread(evlist, prot, mask);
> + return perf_evlist__mmap_per_thread(evlist);
>
> - return perf_evlist__mmap_per_cpu(evlist, prot, mask);
> + return perf_evlist__mmap_per_cpu(evlist);
> }
>
> int perf_evlist__create_maps(struct perf_evlist *evlist, pid_t target_pid,
> diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
> index 1779ffe..3784273 100644
> --- a/tools/perf/util/evlist.h
> +++ b/tools/perf/util/evlist.h
> @@ -18,7 +18,7 @@ struct perf_evlist {
> int nr_entries;
> int nr_fds;
> int nr_mmaps;
> - int mmap_len;
> + int pages;
> bool overwrite;
> union perf_event event_copy;
> struct perf_mmap *mmap;
> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> new file mode 100644
> index 0000000..45e62a2
> --- /dev/null
> +++ b/tools/perf/util/mmap.c
> @@ -0,0 +1,138 @@
> +#include <string.h>
> +#include <stdio.h>
> +#include "mmap.h"
> +
> +int perf_mmap__open(struct perf_mmap *m, int fd, bool overwrite, int pages)
> +{
> + unsigned int page_size = sysconf(_SC_PAGE_SIZE);
> + int mask, len, prot;
> + void *base;
> +
> + mask = pages * page_size - 1;
> + len = (pages + 1) * page_size;
> + prot = PROT_READ | (overwrite ? 0 : PROT_WRITE);
> +
> + base = mmap(NULL, len, prot, MAP_SHARED, fd, 0);
> + if (base == MAP_FAILED)
> + return -1;
> +
> + memset(m, 0, sizeof(*m));
> + m->mask = mask;
> + m->len = len;
> + m->base = base;
> + m->fd = fd;
> + m->owrt = overwrite;
> + return 0;
> +}
> +
> +int perf_mmap__close(struct perf_mmap *m)
> +{
> + int ret = munmap(m->base, m->len);
> +
> + memset(m, 0x0, sizeof(*m));
> + return ret;
> +}
> +
> +int perf_mmap__process(struct perf_mmap *md, perf_mmap_process_t process)
> +{
> + unsigned int head, old, page_size = sysconf(_SC_PAGE_SIZE);
> + unsigned char *data = md->base + page_size;
> + unsigned long size;
> + void *buf;
> +
> + head = perf_mmap__read_head(md);
> + old = md->prev;
> +
> + if (old == head)
> + return 0;
> +
> + size = head - old;
> +
> + if ((old & md->mask) + size != (head & md->mask)) {
> + buf = &data[old & md->mask];
> + size = md->mask + 1 - (old & md->mask);
> + old += size;
> +
> + process(md, buf, size);
> + }
> +
> + buf = &data[old & md->mask];
> + size = head - old;
> + old += size;
> +
> + process(md, buf, size);
> +
> + md->prev = old;
> + perf_mmap__write_tail(md, old);
> + return 1;
> +}
> +
> +union perf_event *perf_mmap__read(struct perf_mmap *md)
> +{
> + unsigned int head, old, page_size = sysconf(_SC_PAGE_SIZE);
> + unsigned char *data = md->base + page_size;
> + union perf_event *event = NULL;
> +
> + head = perf_mmap__read_head(md);
> + old = md->prev;
> +
> + if (md->owrt) {
> + /*
> + * If we're further behind than half the buffer, there's
> + * a chance the writer will bite our tail and mess up the
> + * samples under us.
> + *
> + * If we somehow ended up ahead of the head, we got messed up.
> + *
> + * In either case, truncate and restart at head.
> + */
> + int diff = head - old;
> + if (diff > md->mask / 2 || diff < 0) {
> + fprintf(stderr, "WARNING: failed to keep up "
> + "with mmap data.\n");
> +
> + /*
> + * head points to a known good entry, start there.
> + */
> + old = head;
> + }
> + }
> +
> + if (old != head) {
> + size_t size;
> +
> + event = (union perf_event *)&data[old & md->mask];
> + size = event->header.size;
> +
> + /*
> + * Event straddles the mmap boundary -- header should always
> + * be inside due to u64 alignment of output.
> + */
> + if ((old & md->mask) + size != ((old + size) & md->mask)) {
> + unsigned int offset = old;
> + unsigned int len = min(sizeof(*event), size), cpy;
> + static union perf_event event_copy;
> + void *dst = &event_copy;
> +
> + do {
> + cpy = min(md->mask + 1 - (offset & md->mask),
> + len);
> + memcpy(dst, &data[offset & md->mask], cpy);
> + offset += cpy;
> + dst += cpy;
> + len -= cpy;
> + } while (len);
> +
> + event = &event_copy;
> + }
> +
> + old += size;
> + }
> +
> + md->prev = old;
> +
> + if (!md->owrt)
> + perf_mmap__write_tail(md, old);
> +
> + return event;
> +}
> diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
> new file mode 100644
> index 0000000..24cf88f
> --- /dev/null
> +++ b/tools/perf/util/mmap.h
> @@ -0,0 +1,45 @@
> +#ifndef __PERF_MMAP_H
> +#define __PERF_MMAP_H
> +
> +#include <sys/mman.h>
> +#include "event.h"
> +#include "../perf.h"
> +
> +struct perf_mmap {
> + void *base;
> + int mask;
> + u_int prev;
> + int len;
> + int fd;
> + bool owrt;
> +};
> +
> +typedef void (*perf_mmap_process_t)(struct perf_mmap *m,
> + void *buf, unsigned long size);
> +
> +int perf_mmap__open(struct perf_mmap *m, int fd, bool overwrite, int pages);
> +int perf_mmap__close(struct perf_mmap *m);
> +int perf_mmap__process(struct perf_mmap *m, perf_mmap_process_t process);
> +union perf_event *perf_mmap__read(struct perf_mmap *md);
> +
> +static inline unsigned int perf_mmap__read_head(struct perf_mmap *mm)
> +{
> + struct perf_event_mmap_page *pc = mm->base;
> + int head = pc->data_head;
> + rmb();
> + return head;
> +}
> +
> +static inline void perf_mmap__write_tail(struct perf_mmap *md,
> + unsigned long tail)
> +{
> + struct perf_event_mmap_page *pc = md->base;
> +
> + /*
> + * ensure all reads are done before we write the tail out.
> + */
> + /* mb(); */
> + pc->data_tail = tail;
> +}
> +
> +#endif /* __PERF_MMAP_H */
> --
> 1.7.4
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