[PATCH] drm/ttm: check if free mem space is under the lower limit
Alex Deucher
alexdeucher at gmail.com
Thu Feb 22 14:05:44 UTC 2018
On Thu, Feb 22, 2018 at 6:43 AM, He, Roger <Hongbo.He at amd.com> wrote:
>
>
> -----Original Message-----
> From: Koenig, Christian
> Sent: Thursday, February 22, 2018 7:28 PM
> To: He, Roger <Hongbo.He at amd.com>; dri-devel at lists.freedesktop.org
> Subject: Re: [PATCH] drm/ttm: check if free mem space is under the lower limit
>
> Am 22.02.2018 um 11:10 schrieb Roger He:
>> the free mem space and the lower limit both include two parts:
>> system memory and swap space.
>>
>> For the OOM triggered by TTM, that is the case as below:
>> first swap space is full of swapped out pages and soon system memory
>> also is filled up with ttm pages. and then any memory allocation
>> request will run into OOM.
>>
>> to cover two cases:
>> a. if no swap disk at all or free swap space is under swap mem
>> limit but available system mem is bigger than sys mem limit,
>> allow TTM allocation;
>>
>> b. if the available system mem is less than sys mem limit but
>> free swap space is bigger than swap mem limit, allow TTM
>> allocation.
>>
>> v2: merge two memory limit(swap and system) into one
>> v3: keep original behavior except ttm_opt_ctx->flags with
>> TTM_OPT_FLAG_FORCE_ALLOC
>> v4: always set force_alloc as tx->flags & TTM_OPT_FLAG_FORCE_ALLOC
>> v5: add an attribute for lower_mem_limit
>>
>> Signed-off-by: Roger He <Hongbo.He at amd.com>
>> ---
>> drivers/gpu/drm/ttm/ttm_memory.c | 94 ++++++++++++++++++++++++++++++++
>> drivers/gpu/drm/ttm/ttm_page_alloc.c | 3 +
>> drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 3 +
>> include/drm/ttm/ttm_memory.h | 5 ++
>> 4 files changed, 105 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_memory.c
>> b/drivers/gpu/drm/ttm/ttm_memory.c
>> index aa0c381..d015e39 100644
>> --- a/drivers/gpu/drm/ttm/ttm_memory.c
>> +++ b/drivers/gpu/drm/ttm/ttm_memory.c
>> @@ -36,6 +36,7 @@
>> #include <linux/mm.h>
>> #include <linux/module.h>
>> #include <linux/slab.h>
>> +#include <linux/swap.h>
>>
>> #define TTM_MEMORY_ALLOC_RETRIES 4
>>
>> @@ -166,6 +167,52 @@ static struct kobj_type ttm_mem_zone_kobj_type = {
>> .default_attrs = ttm_mem_zone_attrs,
>> };
>>
>> +static struct attribute ttm_mem_global_lower_mem_limit = {
>> + .name = "lower_mem_limit",
>> + .mode = S_IRUGO | S_IWUSR
>> +};
>> +
>> +static ssize_t ttm_mem_global_show(struct kobject *kobj,
>> + struct attribute *attr,
>> + char *buffer)
>> +{
>> + struct ttm_mem_global *glob =
>> + container_of(kobj, struct ttm_mem_global, kobj);
>> + uint64_t val = 0;
>> +
>> + spin_lock(&glob->lock);
>> + val = glob->lower_mem_limit;
>> + spin_unlock(&glob->lock);
>> +
>> + return snprintf(buffer, PAGE_SIZE, "%llu\n",
>> + (unsigned long long) val << 2);
>
> What is that shift good for?
>
> Because the unit of lower_mem_limit is 4KB, so (val << 2) can get KB for consistent with other parameters as below(all are showed with KB bytes.):
Might want to add a comment or use a define for the shift so others
doen't get confused in the future.
Alex
>
> static struct attribute *ttm_mem_zone_attrs[] = {
> &ttm_mem_sys,
> &ttm_mem_emer,
> &ttm_mem_max,
> &ttm_mem_swap,
> &ttm_mem_used,
> NULL
> };
>
>> +}
>> +
>> +static ssize_t ttm_mem_global_store(struct kobject *kobj,
>> + struct attribute *attr,
>> + const char *buffer,
>> + size_t size)
>> +{
>> + int chars;
>> + uint64_t val64;
>> + unsigned long val;
>> + struct ttm_mem_global *glob =
>> + container_of(kobj, struct ttm_mem_global, kobj);
>> +
>> + chars = sscanf(buffer, "%lu", &val);
>> + if (chars == 0)
>> + return size;
>> +
>> + val64 = val;
>> + val64 >>= 2;
>
> Dito?
> Covert from KB to 4K page size here.
>
>> +
>> + spin_lock(&glob->lock);
>> + glob->lower_mem_limit = val64;
>> + spin_unlock(&glob->lock);
>> +
>> + return size;
>> +}
>> +
>> static void ttm_mem_global_kobj_release(struct kobject *kobj)
>> {
>> struct ttm_mem_global *glob =
>> @@ -174,8 +221,20 @@ static void ttm_mem_global_kobj_release(struct kobject *kobj)
>> kfree(glob);
>> }
>>
>> +static struct attribute *ttm_mem_global_attrs[] = {
>> + &ttm_mem_global_lower_mem_limit,
>> + NULL
>> +};
>> +
>> +static const struct sysfs_ops ttm_mem_global_ops = {
>> + .show = &ttm_mem_global_show,
>> + .store = &ttm_mem_global_store,
>> +};
>> +
>> static struct kobj_type ttm_mem_glob_kobj_type = {
>> .release = &ttm_mem_global_kobj_release,
>> + .sysfs_ops = &ttm_mem_global_ops,
>> + .default_attrs = ttm_mem_global_attrs,
>> };
>>
>> static bool ttm_zones_above_swap_target(struct ttm_mem_global *glob,
>> @@ -375,6 +434,11 @@ int ttm_mem_global_init(struct ttm_mem_global
>> *glob)
>>
>> si_meminfo(&si);
>>
>> + /* lower limit of swap space and 256MB is enough */
>> + glob->lower_mem_limit = 256 << 8;
>> + /* lower limit of ram and keep consistent with each zone->emer_mem */
>> + glob->lower_mem_limit += si.totalram >> 2;
>> +
>
> Mhm, I fear we need to set this to zero by default.
>
> Do you mean: glob->lower_mem_limit = 0 ?
> I don't get your point here. Then how amdgpu set it with above value to prevent OOM?
>
> Thanks
> Roger(Hongbo.He)
>> ret = ttm_mem_init_kernel_zone(glob, &si);
>> if (unlikely(ret != 0))
>> goto out_no_zone;
>> @@ -469,6 +533,36 @@ void ttm_mem_global_free(struct ttm_mem_global *glob,
>> }
>> EXPORT_SYMBOL(ttm_mem_global_free);
>>
>> +/*
>> + * check if the available mem is under lower memory limit
>> + *
>> + * a. if no swap disk at all or free swap space is under
>> +swap_mem_limit
>> + * but available system mem is bigger than sys_mem_limit, allow TTM
>> + * allocation;
>> + *
>> + * b. if the available system mem is less than sys_mem_limit but free
>> + * swap disk is bigger than swap_mem_limit, allow TTM allocation.
>> + */
>> +bool
>> +ttm_check_under_lowerlimit(struct ttm_mem_global *glob,
>> + uint64_t num_pages,
>> + struct ttm_operation_ctx *ctx)
>> +{
>> + bool ret = false;
>> + int64_t available;
>> +
>> + if (ctx->flags & TTM_OPT_FLAG_FORCE_ALLOC)
>> + return false;
>> +
>> + available = get_nr_swap_pages() + si_mem_available();
>> + available -= num_pages;
>> + if (available < glob->lower_mem_limit)
>> + ret = true;
>> +
>> + return ret;
>
> Don't use a local variable, just use "return true" / "return false;".
>
> Regards,
> Christian.
>
>> +}
>> +EXPORT_SYMBOL(ttm_check_under_lowerlimit);
>> +
>> static int ttm_mem_global_reserve(struct ttm_mem_global *glob,
>> struct ttm_mem_zone *single_zone,
>> uint64_t amount, bool reserve) diff --git
>> a/drivers/gpu/drm/ttm/ttm_page_alloc.c
>> b/drivers/gpu/drm/ttm/ttm_page_alloc.c
>> index 5edcd89..c9d8903 100644
>> --- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
>> +++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c
>> @@ -1100,6 +1100,9 @@ int ttm_pool_populate(struct ttm_tt *ttm, struct ttm_operation_ctx *ctx)
>> if (ttm->state != tt_unpopulated)
>> return 0;
>>
>> + if (ttm_check_under_lowerlimit(mem_glob, ttm->num_pages, ctx))
>> + return -ENOMEM;
>> +
>> ret = ttm_get_pages(ttm->pages, ttm->num_pages, ttm->page_flags,
>> ttm->caching_state);
>> if (unlikely(ret != 0)) {
>> diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
>> b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
>> index b122f6e..37e03d9 100644
>> --- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
>> +++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
>> @@ -940,6 +940,9 @@ int ttm_dma_populate(struct ttm_dma_tt *ttm_dma, struct device *dev,
>> if (ttm->state != tt_unpopulated)
>> return 0;
>>
>> + if (ttm_check_under_lowerlimit(mem_glob, num_pages, ctx))
>> + return -ENOMEM;
>> +
>> INIT_LIST_HEAD(&ttm_dma->pages_list);
>> i = 0;
>>
>> diff --git a/include/drm/ttm/ttm_memory.h
>> b/include/drm/ttm/ttm_memory.h index 8936285..737b5fe 100644
>> --- a/include/drm/ttm/ttm_memory.h
>> +++ b/include/drm/ttm/ttm_memory.h
>> @@ -49,6 +49,8 @@
>> * @work: The workqueue callback for the shrink queue.
>> * @lock: Lock to protect the @shrink - and the memory accounting members,
>> * that is, essentially the whole structure with some exceptions.
>> + * @lower_mem_limit: include lower limit of swap space and lower
>> + limit of
>> + * system memory.
>> * @zones: Array of pointers to accounting zones.
>> * @num_zones: Number of populated entries in the @zones array.
>> * @zone_kernel: Pointer to the kernel zone.
>> @@ -67,6 +69,7 @@ struct ttm_mem_global {
>> struct workqueue_struct *swap_queue;
>> struct work_struct work;
>> spinlock_t lock;
>> + uint64_t lower_mem_limit;
>> struct ttm_mem_zone *zones[TTM_MEM_MAX_ZONES];
>> unsigned int num_zones;
>> struct ttm_mem_zone *zone_kernel;
>> @@ -90,4 +93,6 @@ extern void ttm_mem_global_free_page(struct ttm_mem_global *glob,
>> struct page *page, uint64_t size);
>> extern size_t ttm_round_pot(size_t size);
>> extern uint64_t ttm_get_kernel_zone_memory_size(struct
>> ttm_mem_global *glob);
>> +extern bool ttm_check_under_lowerlimit(struct ttm_mem_global *glob,
>> + uint64_t num_pages, struct ttm_operation_ctx *ctx);
>> #endif
>
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