s390/cpum_sf: Dynamically extend the sampling buffer if overflows occur
Improve the sampling buffer allocation and add a function to reallocate and
increase the sampling buffer structure. The number of allocated buffer elements
(sample-data-blocks) are accounted. You can control the minimum and maximum
number these sample-data-blocks through the cpum_sfb_size kernel parameter.
The number hardware sample overflows (if any) are also accounted and stored
per perf event. During the PMU disable/enable calls, the accumulated overflow
counter is analyzed and, if necessary, the sampling buffer is dynamically
increased.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/perf_event.h b/arch/s390/include/asm/perf_event.h
index 23d2dfa..99d7f4e 100644
--- a/arch/s390/include/asm/perf_event.h
+++ b/arch/s390/include/asm/perf_event.h
@@ -49,6 +49,10 @@
#define PERF_CPUM_SF_MAX_CTR 1
#define PERF_EVENT_CPUM_SF 0xB0000UL /* Raw event ID */
+#define REG_NONE 0
+#define REG_OVERFLOW 1
+#define OVERFLOW_REG(hwc) ((hwc)->extra_reg.config)
+#define SFB_ALLOC_REG(hwc) ((hwc)->extra_reg.alloc)
#define TEAR_REG(hwc) ((hwc)->last_tag)
#define SAMPL_RATE(hwc) ((hwc)->event_base)
diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
index ae5e019..ea16560 100644
--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -17,6 +17,8 @@
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/moduleparam.h>
#include <asm/cpu_mf.h>
#include <asm/irq.h>
#include <asm/debug.h>
@@ -26,34 +28,54 @@
* At least one table is required for the sampling buffer structure.
* A single table contains up to 511 pointers to sample-data-blocks.
*/
-#define CPUM_SF_MIN_SDBT 1
+#define CPUM_SF_MIN_SDBT 1
-/* Minimum number of sample-data-blocks:
- * The minimum designates a single page for sample-data-block, i.e.,
- * up to 126 sample-data-blocks with a size of 32 bytes (bsdes).
+/* Number of sample-data-blocks per sample-data-block-table (SDBT):
+ * The table contains SDB origin (8 bytes) and one SDBT origin that
+ * points to the next table.
*/
-#define CPUM_SF_MIN_SDB 126
+#define CPUM_SF_SDB_PER_TABLE ((PAGE_SIZE - 8) / 8)
-/* Maximum number of sample-data-blocks:
- * The maximum number designates approx. 256K per CPU including
- * the given number of sample-data-blocks and taking the number
- * of sample-data-block tables into account.
+/* Maximum page offset for an SDBT table-link entry:
+ * If this page offset is reached, a table-link entry to the next SDBT
+ * must be added.
+ */
+#define CPUM_SF_SDBT_TL_OFFSET (CPUM_SF_SDB_PER_TABLE * 8)
+static inline int require_table_link(const void *sdbt)
+{
+ return ((unsigned long) sdbt & ~PAGE_MASK) == CPUM_SF_SDBT_TL_OFFSET;
+}
+
+/* Minimum and maximum sampling buffer sizes:
*
- * Later, this number can be increased for extending the sampling
- * buffer, for example, by factor 2 (512K) or 4 (1M).
+ * This number represents the maximum size of the sampling buffer
+ * taking the number of sample-data-block-tables into account.
+ *
+ * Sampling buffer size Buffer characteristics
+ * ---------------------------------------------------
+ * 64KB == 16 pages (4KB per page)
+ * 1 page for SDB-tables
+ * 15 pages for SDBs
+ *
+ * 32MB == 8192 pages (4KB per page)
+ * 16 pages for SDB-tables
+ * 8176 pages for SDBs
*/
-#define CPUM_SF_MAX_SDB 6471
+static unsigned long __read_mostly CPUM_SF_MIN_SDB = 15;
+static unsigned long __read_mostly CPUM_SF_MAX_SDB = 8176;
struct sf_buffer {
- unsigned long sdbt; /* Sample-data-block-table origin */
+ unsigned long *sdbt; /* Sample-data-block-table origin */
/* buffer characteristics (required for buffer increments) */
- unsigned long num_sdb; /* Number of sample-data-blocks */
- unsigned long tail; /* last sample-data-block-table */
+ unsigned long num_sdb; /* Number of sample-data-blocks */
+ unsigned long num_sdbt; /* Number of sample-data-block-tables */
+ unsigned long *tail; /* last sample-data-block-table */
};
struct cpu_hw_sf {
/* CPU-measurement sampling information block */
struct hws_qsi_info_block qsi;
+ /* CPU-measurement sampling control block */
struct hws_lsctl_request_block lsctl;
struct sf_buffer sfb; /* Sampling buffer */
unsigned int flags; /* Status flags */
@@ -65,11 +87,22 @@
static debug_info_t *sfdbg;
/*
+ * sf_disable() - Switch off sampling facility
+ */
+static int sf_disable(void)
+{
+ struct hws_lsctl_request_block sreq;
+
+ memset(&sreq, 0, sizeof(sreq));
+ return lsctl(&sreq);
+}
+
+/*
* sf_buffer_available() - Check for an allocated sampling buffer
*/
static int sf_buffer_available(struct cpu_hw_sf *cpuhw)
{
- return (cpuhw->sfb.sdbt) ? 1 : 0;
+ return !!cpuhw->sfb.sdbt;
}
/*
@@ -77,32 +110,32 @@
*/
static void free_sampling_buffer(struct sf_buffer *sfb)
{
- unsigned long sdbt, *curr;
+ unsigned long *sdbt, *curr;
if (!sfb->sdbt)
return;
sdbt = sfb->sdbt;
- curr = (unsigned long *) sdbt;
+ curr = sdbt;
- /* we'll free the SDBT after all SDBs are processed... */
+ /* Free the SDBT after all SDBs are processed... */
while (1) {
if (!*curr || !sdbt)
break;
- /* watch for link entry reset if found */
+ /* Process table-link entries */
if (is_link_entry(curr)) {
curr = get_next_sdbt(curr);
if (sdbt)
- free_page(sdbt);
+ free_page((unsigned long) sdbt);
- /* we are done if we reach the origin */
- if ((unsigned long) curr == sfb->sdbt)
+ /* If the origin is reached, sampling buffer is freed */
+ if (curr == sfb->sdbt)
break;
else
- sdbt = (unsigned long) curr;
+ sdbt = curr;
} else {
- /* process SDB pointer */
+ /* Process SDB pointer */
if (*curr) {
free_page(*curr);
curr++;
@@ -111,10 +144,106 @@
}
debug_sprintf_event(sfdbg, 5,
- "free_sampling_buffer: freed sdbt=%0lx\n", sfb->sdbt);
+ "free_sampling_buffer: freed sdbt=%p\n", sfb->sdbt);
memset(sfb, 0, sizeof(*sfb));
}
+static int alloc_sample_data_block(unsigned long *sdbt, gfp_t gfp_flags)
+{
+ unsigned long sdb, *trailer;
+
+ /* Allocate and initialize sample-data-block */
+ sdb = get_zeroed_page(gfp_flags);
+ if (!sdb)
+ return -ENOMEM;
+ trailer = trailer_entry_ptr(sdb);
+ *trailer = SDB_TE_ALERT_REQ_MASK;
+
+ /* Link SDB into the sample-data-block-table */
+ *sdbt = sdb;
+
+ return 0;
+}
+
+/*
+ * realloc_sampling_buffer() - extend sampler memory
+ *
+ * Allocates new sample-data-blocks and adds them to the specified sampling
+ * buffer memory.
+ *
+ * Important: This modifies the sampling buffer and must be called when the
+ * sampling facility is disabled.
+ *
+ * Returns zero on success, non-zero otherwise.
+ */
+static int realloc_sampling_buffer(struct sf_buffer *sfb,
+ unsigned long num_sdb, gfp_t gfp_flags)
+{
+ int i, rc;
+ unsigned long *new, *tail;
+
+ if (!sfb->sdbt || !sfb->tail)
+ return -EINVAL;
+
+ if (!is_link_entry(sfb->tail))
+ return -EINVAL;
+
+ /* Append to the existing sampling buffer, overwriting the table-link
+ * register.
+ * The tail variables always points to the "tail" (last and table-link)
+ * entry in an SDB-table.
+ */
+ tail = sfb->tail;
+
+ /* Do a sanity check whether the table-link entry points to
+ * the sampling buffer origin.
+ */
+ if (sfb->sdbt != get_next_sdbt(tail)) {
+ debug_sprintf_event(sfdbg, 3, "realloc_sampling_buffer: "
+ "sampling buffer is not linked: origin=%p"
+ "tail=%p\n",
+ (void *) sfb->sdbt, (void *) tail);
+ return -EINVAL;
+ }
+
+ /* Allocate remaining SDBs */
+ rc = 0;
+ for (i = 0; i < num_sdb; i++) {
+ /* Allocate a new SDB-table if it is full. */
+ if (require_table_link(tail)) {
+ new = (unsigned long *) get_zeroed_page(gfp_flags);
+ if (!new) {
+ rc = -ENOMEM;
+ break;
+ }
+ sfb->num_sdbt++;
+ /* Link current page to tail of chain */
+ *tail = (unsigned long)(void *) new + 1;
+ tail = new;
+ }
+
+ /* Allocate a new sample-data-block.
+ * If there is not enough memory, stop the realloc process
+ * and simply use what was allocated. If this is a temporary
+ * issue, a new realloc call (if required) might succeed.
+ */
+ rc = alloc_sample_data_block(tail, gfp_flags);
+ if (rc)
+ break;
+ sfb->num_sdb++;
+ tail++;
+ }
+
+ /* Link sampling buffer to its origin */
+ *tail = (unsigned long) sfb->sdbt + 1;
+ sfb->tail = tail;
+
+ debug_sprintf_event(sfdbg, 4, "realloc_sampling_buffer: new buffer"
+ " settings: sdbt=%lu sdb=%lu\n",
+ sfb->num_sdbt, sfb->num_sdb);
+ return rc;
+}
+
/*
* allocate_sampling_buffer() - allocate sampler memory
*
@@ -128,75 +257,74 @@
*/
static int alloc_sampling_buffer(struct sf_buffer *sfb, unsigned long num_sdb)
{
- int j, k, rc;
- unsigned long *sdbt, *tail, *trailer;
- unsigned long sdb;
- unsigned long num_sdbt, sdb_per_table;
+ int rc;
if (sfb->sdbt)
return -EINVAL;
+
+ /* Allocate the sample-data-block-table origin */
+ sfb->sdbt = (unsigned long *) get_zeroed_page(GFP_KERNEL);
+ if (!sfb->sdbt)
+ return -ENOMEM;
sfb->num_sdb = 0;
+ sfb->num_sdbt = 1;
- /* Compute the number of required sample-data-block-tables (SDBT) */
- num_sdbt = num_sdb / ((PAGE_SIZE - 8) / 8);
- if (num_sdbt < CPUM_SF_MIN_SDBT)
- num_sdbt = CPUM_SF_MIN_SDBT;
- sdb_per_table = (PAGE_SIZE - 8) / 8;
+ /* Link the table origin to point to itself to prepare for
+ * realloc_sampling_buffer() invocation.
+ */
+ sfb->tail = sfb->sdbt;
+ *sfb->tail = (unsigned long)(void *) sfb->sdbt + 1;
- debug_sprintf_event(sfdbg, 4, "alloc_sampling_buffer: num_sdbt=%lu "
- "num_sdb=%lu sdb_per_table=%lu\n",
- num_sdbt, num_sdb, sdb_per_table);
- sdbt = NULL;
- tail = sdbt;
-
- for (j = 0; j < num_sdbt; j++) {
- sdbt = (unsigned long *) get_zeroed_page(GFP_KERNEL);
- if (!sdbt) {
- rc = -ENOMEM;
- goto allocate_sdbt_error;
- }
-
- /* save origin of sample-data-block-table */
- if (!sfb->sdbt)
- sfb->sdbt = (unsigned long) sdbt;
-
- /* link current page to tail of chain */
- if (tail)
- *tail = (unsigned long)(void *) sdbt + 1;
-
- for (k = 0; k < num_sdb && k < sdb_per_table; k++) {
- /* get and set SDB page */
- sdb = get_zeroed_page(GFP_KERNEL);
- if (!sdb) {
- rc = -ENOMEM;
- goto allocate_sdbt_error;
- }
- *sdbt = sdb;
- trailer = trailer_entry_ptr(*sdbt);
- *trailer = SDB_TE_ALERT_REQ_MASK;
- sdbt++;
- }
- num_sdb -= k;
- sfb->num_sdb += k; /* count allocated sdb's */
- tail = sdbt;
- }
-
- rc = 0;
- if (tail)
- *tail = sfb->sdbt + 1;
- sfb->tail = (unsigned long) (void *)tail;
-
-allocate_sdbt_error:
- if (rc)
+ /* Allocate requested number of sample-data-blocks */
+ rc = realloc_sampling_buffer(sfb, num_sdb, GFP_KERNEL);
+ if (rc) {
free_sampling_buffer(sfb);
- else
+ debug_sprintf_event(sfdbg, 4, "alloc_sampling_buffer: "
+ "realloc_sampling_buffer failed with rc=%i\n", rc);
+ } else
debug_sprintf_event(sfdbg, 4,
- "alloc_sampling_buffer: tear=%0lx dear=%0lx\n",
- sfb->sdbt, *(unsigned long *) sfb->sdbt);
+ "alloc_sampling_buffer: tear=%p dear=%p\n",
+ sfb->sdbt, (void *) *sfb->sdbt);
return rc;
}
-static int allocate_sdbt(struct cpu_hw_sf *cpuhw, const struct hw_perf_event *hwc)
+static void sfb_set_limits(unsigned long min, unsigned long max)
+{
+ CPUM_SF_MIN_SDB = min;
+ CPUM_SF_MAX_SDB = max;
+}
+
+static unsigned long sfb_pending_allocs(struct sf_buffer *sfb,
+ struct hw_perf_event *hwc)
+{
+ if (!sfb->sdbt)
+ return SFB_ALLOC_REG(hwc);
+ if (SFB_ALLOC_REG(hwc) > sfb->num_sdb)
+ return SFB_ALLOC_REG(hwc) - sfb->num_sdb;
+ return 0;
+}
+
+static int sfb_has_pending_allocs(struct sf_buffer *sfb,
+ struct hw_perf_event *hwc)
+{
+ return sfb_pending_allocs(sfb, hwc) > 0;
+}
+
+static void sfb_account_allocs(unsigned long num, struct hw_perf_event *hwc)
+{
+ /* Limit the number SDBs to not exceed the maximum */
+ num = min_t(unsigned long, num, CPUM_SF_MAX_SDB - SFB_ALLOC_REG(hwc));
+ if (num)
+ SFB_ALLOC_REG(hwc) += num;
+}
+
+static void sfb_init_allocs(unsigned long num, struct hw_perf_event *hwc)
+{
+ SFB_ALLOC_REG(hwc) = 0;
+ sfb_account_allocs(num, hwc);
+}
+
+static int allocate_sdbt(struct cpu_hw_sf *cpuhw, struct hw_perf_event *hwc)
{
unsigned long n_sdb, freq;
unsigned long factor;
@@ -225,19 +353,125 @@
if (n_sdb < CPUM_SF_MIN_SDB)
n_sdb = CPUM_SF_MIN_SDB;
- /* Return if there is already a sampling buffer allocated.
- * XXX Remove this later and check number of available and
- * required sdb's and, if necessary, increase the sampling buffer.
+ /* If there is already a sampling buffer allocated, it is very likely
+ * that the sampling facility is enabled too. If the event to be
+ * initialized requires a greater sampling buffer, the allocation must
+ * be postponed. Changing the sampling buffer requires the sampling
+ * facility to be in the disabled state. So, account the number of
+ * required SDBs and let cpumsf_pmu_enable() resize the buffer just
+ * before the event is started.
*/
+ sfb_init_allocs(n_sdb, hwc);
if (sf_buffer_available(cpuhw))
return 0;
debug_sprintf_event(sfdbg, 3,
- "allocate_sdbt: rate=%lu f=%lu sdb=%lu/%i cpuhw=%p\n",
+ "allocate_sdbt: rate=%lu f=%lu sdb=%lu/%lu cpuhw=%p\n",
SAMPL_RATE(hwc), freq, n_sdb, CPUM_SF_MAX_SDB, cpuhw);
return alloc_sampling_buffer(&cpuhw->sfb,
- min_t(unsigned long, n_sdb, CPUM_SF_MAX_SDB));
+ sfb_pending_allocs(&cpuhw->sfb, hwc));
+}
+
+static unsigned long min_percent(unsigned int percent, unsigned long base,
+ unsigned long min)
+{
+ return min_t(unsigned long, min, DIV_ROUND_UP(percent * base, 100));
+}
+
+static unsigned long compute_sfb_extent(unsigned long ratio, unsigned long base)
+{
+ /* Use a percentage-based approach to extend the sampling facility
+ * buffer. Accept up to 5% sample data loss.
+ * Vary the extents between 1% to 5% of the current number of
+ * sample-data-blocks.
+ */
+ if (ratio <= 5)
+ return 0;
+ if (ratio <= 25)
+ return min_percent(1, base, 1);
+ if (ratio <= 50)
+ return min_percent(1, base, 1);
+ if (ratio <= 75)
+ return min_percent(2, base, 2);
+ if (ratio <= 100)
+ return min_percent(3, base, 3);
+ if (ratio <= 250)
+ return min_percent(4, base, 4);
+
+ return min_percent(5, base, 8);
+}
+
+static void sfb_account_overflows(struct cpu_hw_sf *cpuhw,
+ struct hw_perf_event *hwc)
+{
+ unsigned long ratio, num;
+
+ if (!OVERFLOW_REG(hwc))
+ return;
+
+ /* The sample_overflow contains the average number of sample data
+ * that has been lost because sample-data-blocks were full.
+ *
+ * Calculate the total number of sample data entries that has been
+ * discarded. Then calculate the ratio of lost samples to total samples
+ * per second in percent.
+ */
+ ratio = DIV_ROUND_UP(100 * OVERFLOW_REG(hwc) * cpuhw->sfb.num_sdb,
+ sample_rate_to_freq(&cpuhw->qsi, SAMPL_RATE(hwc)));
+
+ /* Compute number of sample-data-blocks */
+ num = compute_sfb_extent(ratio, cpuhw->sfb.num_sdb);
+ if (num)
+ sfb_account_allocs(num, hwc);
+
+ debug_sprintf_event(sfdbg, 5, "sfb: overflow: overflow=%llu ratio=%lu"
+ " num=%lu\n", OVERFLOW_REG(hwc), ratio, num);
+ OVERFLOW_REG(hwc) = 0;
+}
+
+/* extend_sampling_buffer() - Extend sampling buffer
+ * @sfb: Sampling buffer structure (for local CPU)
+ * @hwc: Perf event hardware structure
+ *
+ * Use this function to extend the sampling buffer based on the overflow counter
+ * and postponed allocation extents stored in the specified Perf event hardware.
+ *
+ * Important: This function disables the sampling facility in order to safely
+ * change the sampling buffer structure. Do not call this function
+ * when the PMU is active.
+ */
+static void extend_sampling_buffer(struct sf_buffer *sfb,
+ struct hw_perf_event *hwc)
+{
+ unsigned long num, num_old;
+ int rc;
+
+ num = sfb_pending_allocs(sfb, hwc);
+ if (!num)
+ return;
+ num_old = sfb->num_sdb;
+
+ /* Disable the sampling facility to reset any states and also
+ * clear pending measurement alerts.
+ */
+ sf_disable();
+
+ /* Extend the sampling buffer.
+ * This memory allocation typically happens in an atomic context when
+ * called by perf. Because this is a reallocation, it is fine if the
+ * new SDB-request cannot be satisfied immediately.
+ */
+ rc = realloc_sampling_buffer(sfb, num, GFP_ATOMIC);
+ if (rc)
+ debug_sprintf_event(sfdbg, 5, "sfb: extend: realloc "
+ "failed with rc=%i\n", rc);
+
+ if (sfb_has_pending_allocs(sfb, hwc))
+ debug_sprintf_event(sfdbg, 5, "sfb: extend: "
+ "req=%lu alloc=%lu remaining=%lu\n",
+ num, sfb->num_sdb - num_old,
+ sfb_pending_allocs(sfb, hwc));
}
@@ -246,18 +480,6 @@
/* Used to avoid races in calling reserve/release_cpumf_hardware */
static DEFINE_MUTEX(pmc_reserve_mutex);
-/*
- * sf_disable() - Switch off sampling facility
- */
-static int sf_disable(void)
-{
- struct hws_lsctl_request_block sreq;
-
- memset(&sreq, 0, sizeof(sreq));
- return lsctl(&sreq);
-}
-
-
#define PMC_INIT 0
#define PMC_RELEASE 1
#define PMC_FAILURE 2
@@ -345,19 +567,17 @@
}
static void hw_reset_registers(struct hw_perf_event *hwc,
- unsigned long sdbt_origin)
+ unsigned long *sdbt_origin)
{
- TEAR_REG(hwc) = sdbt_origin; /* (re)set to first sdb table */
+ /* (Re)set to first sample-data-block-table */
+ TEAR_REG(hwc) = (unsigned long) sdbt_origin;
}
static unsigned long hw_limit_rate(const struct hws_qsi_info_block *si,
unsigned long rate)
{
- if (rate < si->min_sampl_rate)
- return si->min_sampl_rate;
- if (rate > si->max_sampl_rate)
- return si->max_sampl_rate;
- return rate;
+ return clamp_t(unsigned long, rate,
+ si->min_sampl_rate, si->max_sampl_rate);
}
static int __hw_perf_event_init(struct perf_event *event)
@@ -448,6 +668,10 @@
SAMPL_RATE(hwc) = rate;
hw_init_period(hwc, SAMPL_RATE(hwc));
+ /* Initialize sample data overflow accounting */
+ hwc->extra_reg.reg = REG_OVERFLOW;
+ OVERFLOW_REG(hwc) = 0;
+
/* Allocate the per-CPU sampling buffer using the CPU information
* from the event. If the event is not pinned to a particular
* CPU (event->cpu == -1; or cpuhw == NULL), allocate sampling
@@ -513,6 +737,7 @@
static void cpumsf_pmu_enable(struct pmu *pmu)
{
struct cpu_hw_sf *cpuhw = &__get_cpu_var(cpu_hw_sf);
+ struct hw_perf_event *hwc;
int err;
if (cpuhw->flags & PMU_F_ENABLED)
@@ -521,6 +746,26 @@
if (cpuhw->flags & PMU_F_ERR_MASK)
return;
+ /* Check whether to extent the sampling buffer.
+ *
+ * Two conditions trigger an increase of the sampling buffer for a
+ * perf event:
+ * 1. Postponed buffer allocations from the event initialization.
+ * 2. Sampling overflows that contribute to pending allocations.
+ *
+ * Note that the extend_sampling_buffer() function disables the sampling
+ * facility, but it can be fully re-enabled using sampling controls that
+ * have been saved in cpumsf_pmu_disable().
+ */
+ if (cpuhw->event) {
+ hwc = &cpuhw->event->hw;
+ /* Account number of overflow-designated buffer extents */
+ sfb_account_overflows(cpuhw, hwc);
+ if (sfb_has_pending_allocs(&cpuhw->sfb, hwc))
+ extend_sampling_buffer(&cpuhw->sfb, hwc);
+ }
+
+ /* (Re)enable the PMU and sampling facility */
cpuhw->flags |= PMU_F_ENABLED;
barrier();
@@ -632,8 +877,6 @@
if (perf_event_overflow(event, &data, ®s)) {
overflow = 1;
event->pmu->stop(event, 0);
- debug_sprintf_event(sfdbg, 4, "perf_push_sample: PMU stopped"
- " because of an event overflow\n");
}
perf_event_update_userpage(event);
@@ -710,11 +953,11 @@
struct hw_perf_event *hwc = &event->hw;
struct hws_trailer_entry *te;
unsigned long *sdbt;
- unsigned long long event_overflow, sampl_overflow;
+ unsigned long long event_overflow, sampl_overflow, num_sdb;
int done;
sdbt = (unsigned long *) TEAR_REG(hwc);
- done = event_overflow = sampl_overflow = 0;
+ done = event_overflow = sampl_overflow = num_sdb = 0;
while (!done) {
/* Get the trailer entry of the sample-data-block */
te = (struct hws_trailer_entry *) trailer_entry_ptr(*sdbt);
@@ -726,17 +969,13 @@
break;
}
- /* Check sample overflow count */
- if (te->overflow) {
- /* Increment sample overflow counter */
- sampl_overflow += te->overflow;
-
- /* XXX: If an sample overflow occurs, increase the
- * sampling buffer. Set a "realloc" flag because
- * the sampler must be re-enabled for changing
- * the sample-data-block-table content.
+ /* Check the sample overflow count */
+ if (te->overflow)
+ /* Account sample overflows and, if a particular limit
+ * is reached, extend the sampling buffer.
+ * For details, see sfb_account_overflows().
*/
- }
+ sampl_overflow += te->overflow;
/* Timestamps are valid for full sample-data-blocks only */
debug_sprintf_event(sfdbg, 6, "hw_perf_event_update: sdbt=%p "
@@ -749,6 +988,7 @@
* is stopped and remaining samples will be discarded.
*/
hw_collect_samples(event, sdbt, &event_overflow);
+ num_sdb++;
/* Reset trailer */
xchg(&te->overflow, 0);
@@ -775,6 +1015,10 @@
flush_all = 1;
}
+ /* Account sample overflows in the event hardware structure */
+ if (sampl_overflow)
+ OVERFLOW_REG(hwc) = DIV_ROUND_UP(OVERFLOW_REG(hwc) +
+ sampl_overflow, 1 + num_sdb);
if (sampl_overflow || event_overflow)
debug_sprintf_event(sfdbg, 4, "hw_perf_event_update: "
"overflow stats: sample=%llu event=%llu\n",
@@ -849,7 +1093,7 @@
*/
cpuhw->lsctl.s = 0;
cpuhw->lsctl.h = 1;
- cpuhw->lsctl.tear = cpuhw->sfb.sdbt;
+ cpuhw->lsctl.tear = (unsigned long) cpuhw->sfb.sdbt;
cpuhw->lsctl.dear = *(unsigned long *) cpuhw->sfb.sdbt;
cpuhw->lsctl.interval = SAMPL_RATE(&event->hw);
hw_reset_registers(&event->hw, cpuhw->sfb.sdbt);
@@ -1018,6 +1262,48 @@
return NOTIFY_OK;
}
+static int param_get_sfb_size(char *buffer, const struct kernel_param *kp)
+{
+ if (!cpum_sf_avail())
+ return -ENODEV;
+ return sprintf(buffer, "%lu,%lu", CPUM_SF_MIN_SDB, CPUM_SF_MAX_SDB);
+}
+
+static int param_set_sfb_size(const char *val, const struct kernel_param *kp)
+{
+ int rc;
+ unsigned long min, max;
+
+ if (!cpum_sf_avail())
+ return -ENODEV;
+ if (!val || !strlen(val))
+ return -EINVAL;
+
+ /* Valid parameter values: "min,max" or "max" */
+ min = CPUM_SF_MIN_SDB;
+ max = CPUM_SF_MAX_SDB;
+ if (strchr(val, ','))
+ rc = (sscanf(val, "%lu,%lu", &min, &max) == 2) ? 0 : -EINVAL;
+ else
+ rc = kstrtoul(val, 10, &max);
+
+ if (min < 2 || min >= max || max > get_num_physpages())
+ rc = -EINVAL;
+ if (rc)
+ return rc;
+
+ sfb_set_limits(min, max);
+ pr_info("Changed sampling buffer settings: min=%lu max=%lu\n",
+ CPUM_SF_MIN_SDB, CPUM_SF_MAX_SDB);
+ return 0;
+}
+
+#define param_check_sfb_size(name, p) __param_check(name, p, void)
+static struct kernel_param_ops param_ops_sfb_size = {
+ .set = param_set_sfb_size,
+ .get = param_get_sfb_size,
+};
+
static int __init init_cpum_sampling_pmu(void)
{
int err;
@@ -1047,3 +1333,4 @@
return err;
}
arch_initcall(init_cpum_sampling_pmu);
+core_param(cpum_sfb_size, CPUM_SF_MAX_SDB, sfb_size, 0640);