[PATCH v2 5/7] ramoops: Split ftrace buffer space into per-CPU zones
From: Joel Fernandes
Date: Thu Oct 20 2016 - 03:35:09 EST
If FTRACE_PER_CPU flag is passed to ramoops pdata, split the space into
multiple zones depending on the number of CPUs.
This speeds up the performance of function tracing by about 280% in my tests as
we avoid the locking. The trade off being lesser space available per CPU. Let
the ramoops user decide which option they want based on pdata flag.
Signed-off-by: Joel Fernandes <joelaf@xxxxxxxxxx>
---
fs/pstore/ram.c | 72 +++++++++++++++++++++++++++++++++++-----------
include/linux/pstore_ram.h | 3 ++
2 files changed, 58 insertions(+), 17 deletions(-)
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 5caa512..5e96f78 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -87,7 +87,7 @@ MODULE_PARM_DESC(ramoops_ecc,
struct ramoops_context {
struct persistent_ram_zone **przs;
struct persistent_ram_zone *cprz;
- struct persistent_ram_zone *fprz;
+ struct persistent_ram_zone **fprzs;
struct persistent_ram_zone *mprz;
phys_addr_t phys_addr;
unsigned long size;
@@ -97,6 +97,7 @@ struct ramoops_context {
size_t ftrace_size;
size_t pmsg_size;
int dump_oops;
+ int flags;
struct persistent_ram_ecc_info ecc_info;
unsigned int max_dump_cnt;
unsigned int dump_write_cnt;
@@ -219,9 +220,17 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
if (!prz_ok(prz))
prz = ramoops_get_next_prz(&cxt->cprz, &cxt->console_read_cnt,
1, id, type, PSTORE_TYPE_CONSOLE, 0);
- if (!prz_ok(prz))
- prz = ramoops_get_next_prz(&cxt->fprz, &cxt->ftrace_read_cnt,
- 1, id, type, PSTORE_TYPE_FTRACE, 0);
+ if (!prz_ok(prz)) {
+ int max = (cxt->flags & FTRACE_PER_CPU) ? nr_cpu_ids : 1;
+ while (cxt->ftrace_read_cnt < max && !prz) {
+ prz = ramoops_get_next_prz(cxt->fprzs,
+ &cxt->ftrace_read_cnt, max, id, type,
+ PSTORE_TYPE_FTRACE, 0);
+ if (!prz_ok(prz))
+ continue;
+ }
+ }
+
if (!prz_ok(prz))
prz = ramoops_get_next_prz(&cxt->mprz, &cxt->pmsg_read_cnt,
1, id, type, PSTORE_TYPE_PMSG, 0);
@@ -283,9 +292,23 @@ static int notrace ramoops_pstore_write_buf(enum pstore_type_id type,
persistent_ram_write(cxt->cprz, buf, size, PSTORE_RAM_LOCK);
return 0;
} else if (type == PSTORE_TYPE_FTRACE) {
- if (!cxt->fprz)
+ int zonenum, lock;
+
+ if (!cxt->fprzs)
return -ENOMEM;
- persistent_ram_write(cxt->fprz, buf, size, PSTORE_RAM_LOCK);
+ /*
+ * If per-cpu buffers, don't lock. Otherwise there's only
+ * 1 zone for ftrace (zone 0) and all CPUs share it, so lock.
+ */
+ if (cxt->flags & FTRACE_PER_CPU) {
+ zonenum = smp_processor_id();
+ lock = PSTORE_RAM_NOLOCK;
+ } else {
+ zonenum = 0;
+ lock = PSTORE_RAM_LOCK;
+ }
+
+ persistent_ram_write(cxt->fprzs[zonenum], buf, size, lock);
return 0;
} else if (type == PSTORE_TYPE_PMSG) {
pr_warn_ratelimited("ramoops: warning: PMSG shouldn't call %s\n",
@@ -352,6 +375,7 @@ static int ramoops_pstore_erase(enum pstore_type_id type, u64 id, int count,
{
struct ramoops_context *cxt = psi->data;
struct persistent_ram_zone *prz;
+ int max;
switch (type) {
case PSTORE_TYPE_DMESG:
@@ -363,7 +387,10 @@ static int ramoops_pstore_erase(enum pstore_type_id type, u64 id, int count,
prz = cxt->cprz;
break;
case PSTORE_TYPE_FTRACE:
- prz = cxt->fprz;
+ max = (cxt->flags & FTRACE_PER_CPU) ? nr_cpu_ids : 1;
+ if (id >= max)
+ return -EINVAL;
+ prz = cxt->fprzs[id];
break;
case PSTORE_TYPE_PMSG:
prz = cxt->mprz;
@@ -394,14 +421,23 @@ static void ramoops_free_przs(struct ramoops_context *cxt)
{
int i;
- if (!cxt->przs)
- return;
+ /* Free dump PRZs */
+ if (cxt->przs) {
+ for (i = 0; i < cxt->max_dump_cnt; i++)
+ persistent_ram_free(cxt->przs[i]);
- for (i = 0; i < cxt->max_dump_cnt; i++)
- persistent_ram_free(cxt->przs[i]);
+ kfree(cxt->przs);
+ cxt->max_dump_cnt = 0;
+ }
- kfree(cxt->przs);
- cxt->max_dump_cnt = 0;
+ /* Free ftrace PRZs */
+ if (cxt->fprzs) {
+ int nr = (cxt->flags & FTRACE_PER_CPU) ? nr_cpu_ids : 1;
+
+ for (i = 0; i < nr; i++)
+ persistent_ram_free(cxt->fprzs[i]);
+ kfree(cxt->fprzs);
+ }
}
static int ramoops_init_przs(struct device *dev, struct ramoops_context *cxt,
@@ -618,6 +654,7 @@ static int ramoops_probe(struct platform_device *pdev)
cxt->ftrace_size = pdata->ftrace_size;
cxt->pmsg_size = pdata->pmsg_size;
cxt->dump_oops = pdata->dump_oops;
+ cxt->flags = pdata->flags;
cxt->ecc_info = pdata->ecc_info;
paddr = cxt->phys_addr;
@@ -633,8 +670,9 @@ static int ramoops_probe(struct platform_device *pdev)
if (err)
goto fail_init_cprz;
- err = ramoops_init_prz(dev, cxt, &cxt->fprz, &paddr, cxt->ftrace_size,
- LINUX_VERSION_CODE);
+ err = ramoops_init_przs(dev, cxt, &cxt->fprzs, &paddr, cxt->ftrace_size,
+ (cxt->flags & FTRACE_PER_CPU) ? nr_cpu_ids : 1,
+ LINUX_VERSION_CODE);
if (err)
goto fail_init_fprz;
@@ -698,7 +736,6 @@ fail_clear:
cxt->pstore.bufsize = 0;
persistent_ram_free(cxt->mprz);
fail_init_mprz:
- persistent_ram_free(cxt->fprz);
fail_init_fprz:
persistent_ram_free(cxt->cprz);
fail_init_cprz:
@@ -717,7 +754,6 @@ static int ramoops_remove(struct platform_device *pdev)
cxt->pstore.bufsize = 0;
persistent_ram_free(cxt->mprz);
- persistent_ram_free(cxt->fprz);
persistent_ram_free(cxt->cprz);
ramoops_free_przs(cxt);
@@ -759,6 +795,8 @@ static void ramoops_register_dummy(void)
dummy_data->ftrace_size = ramoops_ftrace_size;
dummy_data->pmsg_size = ramoops_pmsg_size;
dummy_data->dump_oops = dump_oops;
+ dummy_data->flags = FTRACE_PER_CPU;
+
/*
* For backwards compatibility ramoops.ecc=1 means 16 bytes ECC
* (using 1 byte for ECC isn't much of use anyway).
diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
index 69f3487..122f78d 100644
--- a/include/linux/pstore_ram.h
+++ b/include/linux/pstore_ram.h
@@ -86,6 +86,8 @@ ssize_t persistent_ram_ecc_string(struct persistent_ram_zone *prz,
* @mem_address physical memory address to contain ramoops
*/
+#define FTRACE_PER_CPU BIT(0)
+
struct ramoops_platform_data {
unsigned long mem_size;
phys_addr_t mem_address;
@@ -95,6 +97,7 @@ struct ramoops_platform_data {
unsigned long ftrace_size;
unsigned long pmsg_size;
int dump_oops;
+ int flags;
struct persistent_ram_ecc_info ecc_info;
};
--
2.7.4