Re: [PATCH V5] mm: compaction: support triggering of proactive compaction by user

Mike Rapoport
2021-07-30T19:32:07Z

On Fri, Jul 30, 2021 at 07:23:27PM +0530, Charan Teja Reddy wrote:
> The proactive compaction[1] gets triggered for every 500msec and run
> compaction on the node for COMPACTION_HPAGE_ORDER (usually order-9)
> pages based on the value set to sysctl.compaction_proactiveness.
> Triggering the compaction for every 500msec in search of
> COMPACTION_HPAGE_ORDER pages is not needed for all applications,
> especially on the embedded system usecases which may have few MB's of
> RAM. Enabling the proactive compaction in its state will endup in
> running almost always on such systems.
>
> Other side, proactive compaction can still be very much useful for
> getting a set of higher order pages in some controllable
> manner(controlled by using the sysctl.compaction_proactiveness). So, on
> systems where enabling the proactive compaction always may proove not
> required, can trigger the same from user space on write to its sysctl
> interface. As an example, say app launcher decide to launch the memory
> heavy application which can be launched fast if it gets more higher
> order pages thus launcher can prepare the system in advance by
> triggering the proactive compaction from userspace.
>
> This triggering of proactive compaction is done on a write to
> sysctl.compaction_proactiveness by user.
>
> [1]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=facdaa917c4d5a376d09d25865f5a863f906234a
>
> Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
> ---
> Changes in V5:
> -- Avoid unnecessary wakeup of proactive compaction when it is disabled.
> -- No changes in the logic of triggering the proactive compaction.
>
> Changes in V4:
> -- Changed the code as the 'proactive_defer' counter is removed.
> -- No changes in the logic of triggering the proactive compaction.
> -- https://lore.kernel.org/patchwork/patch/1448777/
>
> Changes in V3:
> -- Fixed review comments from Valstimil and others.
> -- https://lore.kernel.org/patchwork/patch/1438211/
>
> Changes in V2:
> -- remove /proc/../proactive_compact_memory interface trigger for proactive compaction
> -- Intention is same that add a way to trigger proactive compaction by user.
> -- https://lore.kernel.org/patchwork/patch/1431283/
>
> changes in V1:
> -- Created the new /proc/sys/vm/proactive_compact_memory in
> interface to trigger proactive compaction from user
> -- https://lore.kernel.org/lkml/1619098678-8501-1-git-send-email-charante@codeaurora.org/
>
> Documentation/admin-guide/sysctl/vm.rst | 3 ++-
> include/linux/compaction.h | 2 ++
> include/linux/mmzone.h | 1 +
> kernel/sysctl.c | 2 +-
> mm/compaction.c | 38 +++++++++++++++++++++++++++++++--
> 5 files changed, 42 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
> index 003d5cc..b526cf6 100644
> --- a/Documentation/admin-guide/sysctl/vm.rst
> +++ b/Documentation/admin-guide/sysctl/vm.rst
> @@ -118,7 +118,8 @@ compaction_proactiveness
>
> This tunable takes a value in the range [0, 100] with a default value of
> 20. This tunable determines how aggressively compaction is done in the
> -background. Setting it to 0 disables proactive compaction.
> +background. On write of non zero value to this tunable will immediately

Nit: I think "Write of non zero ..."

> +trigger the proactive compaction. Setting it to 0 disables proactive compaction.
>
> Note that compaction has a non-trivial system-wide impact as pages
> belonging to different processes are moved around, which could also lead
> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> index c24098c..34bce35 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -84,6 +84,8 @@ static inline unsigned long compact_gap(unsigned int order)
> extern unsigned int sysctl_compaction_proactiveness;
> extern int sysctl_compaction_handler(struct ctl_table *table, int write,
> void *buffer, size_t *length, loff_t *ppos);
> +extern int compaction_proactiveness_sysctl_handler(struct ctl_table *table,
> + int write, void *buffer, size_t *length, loff_t *ppos);
> extern int sysctl_extfrag_threshold;
> extern int sysctl_compact_unevictable_allowed;
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 4610750..6a1d79d 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -853,6 +853,7 @@ typedef struct pglist_data {
> enum zone_type kcompactd_highest_zoneidx;
> wait_queue_head_t kcompactd_wait;
> struct task_struct *kcompactd;
> + bool proactive_compact_trigger;
> #endif
> /*
> * This is a per-node reserve of pages that are not available
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 82d6ff6..65bc6f7 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2871,7 +2871,7 @@ static struct ctl_table vm_table[] = {
> .data = &sysctl_compaction_proactiveness,
> .maxlen = sizeof(sysctl_compaction_proactiveness),
> .mode = 0644,
> - .proc_handler = proc_dointvec_minmax,
> + .proc_handler = compaction_proactiveness_sysctl_handler,
> .extra1 = SYSCTL_ZERO,
> .extra2 = &one_hundred,
> },
> diff --git a/mm/compaction.c b/mm/compaction.c
> index f984ad0..fbc60f9 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -2700,6 +2700,30 @@ static void compact_nodes(void)
> */
> unsigned int __read_mostly sysctl_compaction_proactiveness = 20;
>
> +int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write,
> + void *buffer, size_t *length, loff_t *ppos)
> +{
> + int rc, nid;
> +
> + rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
> + if (rc)
> + return rc;
> +
> + if (write && sysctl_compaction_proactiveness) {
> + for_each_online_node(nid) {
> + pg_data_t *pgdat = NODE_DATA(nid);
> +
> + if (pgdat->proactive_compact_trigger)
> + continue;
> +
> + pgdat->proactive_compact_trigger = true;
> + wake_up_interruptible(&pgdat->kcompactd_wait);
> + }
> + }
> +
> + return 0;
> +}
> +
> /*
> * This is the entry point for compacting all nodes via
> * /proc/sys/vm/compact_memory
> @@ -2744,7 +2768,8 @@ void compaction_unregister_node(struct node *node)
>
> static inline bool kcompactd_work_requested(pg_data_t *pgdat)
> {
> - return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
> + return pgdat->kcompactd_max_order > 0 || kthread_should_stop() ||
> + pgdat->proactive_compact_trigger;
> }
>
> static bool kcompactd_node_suitable(pg_data_t *pgdat)
> @@ -2895,9 +2920,16 @@ static int kcompactd(void *p)
> while (!kthread_should_stop()) {
> unsigned long pflags;
>
> + /*
> + * Avoid the unnecessary wakeup for proactive compaction
> + * when it is disabled.
> + */
> + if (!sysctl_compaction_proactiveness)
> + timeout = MAX_SCHEDULE_TIMEOUT;
> trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
> if (wait_event_freezable_timeout(pgdat->kcompactd_wait,
> - kcompactd_work_requested(pgdat), timeout)) {
> + kcompactd_work_requested(pgdat), timeout) &&
> + !pgdat->proactive_compact_trigger) {
>
> psi_memstall_enter(&pflags);
> kcompactd_do_work(pgdat);
> @@ -2932,6 +2964,8 @@ static int kcompactd(void *p)
> timeout =
> default_timeout << COMPACT_MAX_DEFER_SHIFT;
> }
> + if (unlikely(pgdat->proactive_compact_trigger))
> + pgdat->proactive_compact_trigger = false;
> }
>
> return 0;
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
> member of the Code Aurora Forum, hosted by The Linux Foundation
>
>

--
Sincerely yours,
Mike.