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Date: Tue, 10 Apr 2018 09:13:11 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Michal Hocko <mhocko@...nel.org>
Cc: Zhaoyang Huang <huangzhaoyang@...il.com>,
Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
Joel Fernandes <joelaf@...gle.com>
Subject: Re: [PATCH v1] ringbuffer: Don't choose the process with adj equal
OOM_SCORE_ADJ_MIN
On Tue, 10 Apr 2018 08:36:25 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:
> On Tue, 10 Apr 2018 14:27:06 +0200
> Michal Hocko <mhocko@...nel.org> wrote:
>
> > I would rather that the code outside of MM not touch implementation
> > details like OOM_SCORE_ADJ_MIN. It is really hard to get rid of abusers
> > whenever you try to change something in MM then. Especially when the
> > usecase is quite dubious.
>
> Fair enough. I was reluctant to use the OOM_SCORE_ADJ_MIN in this case.
>
> Perhaps I can create an option that lets users decide how they want to
> allocate.
>
> For people like Joel, it will try hard (by default) and set oom_origin,
> but the user could also set an option "no_mem_reclaim", where it will
> not set oom_origin, but will also use NORETRY as well, where it wont
> trigger OOM and will not be the designated victim of OOM. But it will
> likely not allocate memory if the system is under heavy use. Then for
> Zhaoyang's tests, all he has to do is to set that option (or clear it,
> if the option is "mem_reclaim", which is what I'll probably call it).
>
Something like this:
-- Steve
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index a0233edc0718..807e2bcb21b3 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -106,7 +106,8 @@ __poll_t ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
void ring_buffer_free(struct ring_buffer *buffer);
-int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, int cpu);
+int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
+ int cpu, int rbflags);
void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val);
@@ -201,6 +202,7 @@ int ring_buffer_print_page_header(struct trace_seq *s);
enum ring_buffer_flags {
RB_FL_OVERWRITE = 1 << 0,
+ RB_FL_NO_RECLAIM = 1 << 1,
};
#ifdef CONFIG_RING_BUFFER
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index c9cb9767d49b..b7fd541ca025 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1160,7 +1160,8 @@ static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
return 0;
}
-static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
+static int __rb_allocate_pages(long nr_pages, struct list_head *pages,
+ int cpu, int rbflags)
{
struct buffer_page *bpage, *tmp;
bool user_thread = current->mm != NULL;
@@ -1185,6 +1186,12 @@ static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
*/
mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
+ /* Do not try hard to get memory, and do not trigger OOM */
+ if (rbflags & RB_FL_NO_RECLAIM) {
+ mflags = GFP_KERNEL | __GFP_NORETRY;
+ user_thread = false;
+ }
+
/*
* If a user thread allocates too much, and si_mem_available()
* reports there's enough memory, even though there is not.
@@ -1232,13 +1239,13 @@ static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
}
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
- unsigned long nr_pages)
+ unsigned long nr_pages, int rbflags)
{
LIST_HEAD(pages);
WARN_ON(!nr_pages);
- if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
+ if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu, rbflags))
return -ENOMEM;
/*
@@ -1297,7 +1304,7 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, long nr_pages, int cpu)
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
INIT_LIST_HEAD(&cpu_buffer->new_pages);
- ret = rb_allocate_pages(cpu_buffer, nr_pages);
+ ret = rb_allocate_pages(cpu_buffer, nr_pages, buffer->flags);
if (ret < 0)
goto fail_free_reader;
@@ -1685,7 +1692,7 @@ static void update_pages_handler(struct work_struct *work)
* Returns 0 on success and < 0 on failure.
*/
int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
- int cpu_id)
+ int cpu_id, int rbflags)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long nr_pages;
@@ -1739,7 +1746,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
*/
INIT_LIST_HEAD(&cpu_buffer->new_pages);
if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
- &cpu_buffer->new_pages, cpu)) {
+ &cpu_buffer->new_pages, cpu, rbflags)) {
/* not enough memory for new pages */
err = -ENOMEM;
goto out_err;
@@ -1795,7 +1802,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
INIT_LIST_HEAD(&cpu_buffer->new_pages);
if (cpu_buffer->nr_pages_to_update > 0 &&
__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
- &cpu_buffer->new_pages, cpu_id)) {
+ &cpu_buffer->new_pages, cpu_id, rbflags)) {
err = -ENOMEM;
goto out_err;
}
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e18e69183c9a..ff0164affe0a 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -250,7 +250,8 @@ unsigned long long ns2usecs(u64 nsec)
TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK | \
TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | \
TRACE_ITER_RECORD_CMD | TRACE_ITER_OVERWRITE | \
- TRACE_ITER_IRQ_INFO | TRACE_ITER_MARKERS)
+ TRACE_ITER_IRQ_INFO | TRACE_ITER_MARKERS | \
+ TRACE_ITER_MEM_RECLAIM)
/* trace_options that are only supported by global_trace */
#define TOP_LEVEL_TRACE_FLAGS (TRACE_ITER_PRINTK | \
@@ -974,7 +975,7 @@ static void free_snapshot(struct trace_array *tr)
* The max_tr ring buffer has some state (e.g. ring->clock) and
* we want preserve it.
*/
- ring_buffer_resize(tr->max_buffer.buffer, 1, RING_BUFFER_ALL_CPUS);
+ ring_buffer_resize(tr->max_buffer.buffer, 1, RING_BUFFER_ALL_CPUS, 0);
set_buffer_entries(&tr->max_buffer, 1);
tracing_reset_online_cpus(&tr->max_buffer);
tr->allocated_snapshot = false;
@@ -1494,7 +1495,9 @@ static int run_tracer_selftest(struct tracer *type)
/* If we expanded the buffers, make sure the max is expanded too */
if (ring_buffer_expanded)
ring_buffer_resize(tr->max_buffer.buffer, trace_buf_size,
- RING_BUFFER_ALL_CPUS);
+ RING_BUFFER_ALL_CPUS,
+ tr->trace_flags & TRACE_ITER_MEM_RECLAIM ?
+ 0 : RB_FL_NO_RECLAIM);
tr->allocated_snapshot = true;
}
#endif
@@ -1520,7 +1523,9 @@ static int run_tracer_selftest(struct tracer *type)
/* Shrink the max buffer again */
if (ring_buffer_expanded)
ring_buffer_resize(tr->max_buffer.buffer, 1,
- RING_BUFFER_ALL_CPUS);
+ RING_BUFFER_ALL_CPUS,
+ tr->trace_flags & TRACE_ITER_MEM_RECLAIM ?
+ 0 : RB_FL_NO_RECLAIM);
}
#endif
@@ -5168,7 +5173,7 @@ static int resize_buffer_duplicate_size(struct trace_buffer *trace_buf,
if (cpu_id == RING_BUFFER_ALL_CPUS) {
for_each_tracing_cpu(cpu) {
ret = ring_buffer_resize(trace_buf->buffer,
- per_cpu_ptr(size_buf->data, cpu)->entries, cpu);
+ per_cpu_ptr(size_buf->data, cpu)->entries, cpu, 0);
if (ret < 0)
break;
per_cpu_ptr(trace_buf->data, cpu)->entries =
@@ -5176,7 +5181,7 @@ static int resize_buffer_duplicate_size(struct trace_buffer *trace_buf,
}
} else {
ret = ring_buffer_resize(trace_buf->buffer,
- per_cpu_ptr(size_buf->data, cpu_id)->entries, cpu_id);
+ per_cpu_ptr(size_buf->data, cpu_id)->entries, cpu_id, 0);
if (ret == 0)
per_cpu_ptr(trace_buf->data, cpu_id)->entries =
per_cpu_ptr(size_buf->data, cpu_id)->entries;
@@ -5202,7 +5207,9 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
if (!tr->trace_buffer.buffer)
return 0;
- ret = ring_buffer_resize(tr->trace_buffer.buffer, size, cpu);
+ ret = ring_buffer_resize(tr->trace_buffer.buffer, size, cpu,
+ tr->trace_flags & TRACE_ITER_MEM_RECLAIM ?
+ 0 : RB_FL_NO_RECLAIM);
if (ret < 0)
return ret;
@@ -5211,7 +5218,9 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
!tr->current_trace->use_max_tr)
goto out;
- ret = ring_buffer_resize(tr->max_buffer.buffer, size, cpu);
+ ret = ring_buffer_resize(tr->max_buffer.buffer, size, cpu,
+ tr->trace_flags & TRACE_ITER_MEM_RECLAIM ?
+ 0 : RB_FL_NO_RECLAIM);
if (ret < 0) {
int r = resize_buffer_duplicate_size(&tr->trace_buffer,
&tr->trace_buffer, cpu);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 6fb46a06c9dc..2c901f52baf2 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1143,6 +1143,7 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
C(IRQ_INFO, "irq-info"), \
C(MARKERS, "markers"), \
C(EVENT_FORK, "event-fork"), \
+ C(MEM_RECLAIM, "mem-reclaim"), \
FUNCTION_FLAGS \
FGRAPH_FLAGS \
STACK_FLAGS \
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