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Date: Wed, 23 Feb 2022 16:12:01 +0900
From: Jonghyeon Kim <tome01@...u.ac.kr>
To: SeongJae Park <sj@...nel.org>
Cc: Jonghyeon Kim <tome01@...u.ac.kr>, Jonathan.Cameron@...wei.com,
amit@...nel.org, benh@...nel.crashing.org, corbet@....net,
david@...hat.com, dwmw@...zon.com, elver@...gle.com,
foersleo@...zon.de, gthelen@...gle.com, markubo@...zon.de,
rientjes@...gle.com, shakeelb@...gle.com, shuah@...nel.org,
linux-damon@...zon.com, linux-mm@...ck.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1 3/3] mm/damon/reclaim: Add per NUMA node proactive
reclamation by DAMON_RECLAIM.
On Wed, Feb 23, 2022 at 02:11:27PM +0900, Jonghyeon Kim wrote:
> On Tue, Feb 22, 2022 at 09:53:38AM +0000, SeongJae Park wrote:
> > On Fri, 18 Feb 2022 19:26:11 +0900 Jonghyeon Kim <tome01@...u.ac.kr> wrote:
> >
> > > To add DAMON_RECLAIM worker threads(kdamond) that do proactive
> > > reclamation per NUMA node, each node must have its own context.
> > > 'per_node' is added to enable it.
> > >
> > > If 'per_node' is true, kdamonds as online NUMA node will be waked up and
> > > start monitoring to proactively reclaim memory. If 'per_node' is false,
> > > only one kdamond thread will start monitoring for all system memory.
> > >
> > > Signed-off-by: Jonghyeon Kim <tome01@...u.ac.kr>
> > > ---
> > > mm/damon/reclaim.c | 147 ++++++++++++++++++++++++++++++++-------------
> > > 1 file changed, 104 insertions(+), 43 deletions(-)
> > >
> > > diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
> > > index b53d9c22fad1..85e8f97dd599 100644
> > > --- a/mm/damon/reclaim.c
> > > +++ b/mm/damon/reclaim.c
> > > @@ -177,13 +177,27 @@ static unsigned long monitor_region_end __read_mostly;
> > > module_param(monitor_region_end, ulong, 0600);
> > >
> > > /*
> > > - * PID of the DAMON thread
> > > + * Enable monitoring memory regions per NUMA node.
> > > *
> > > - * If DAMON_RECLAIM is enabled, this becomes the PID of the worker thread.
> > > + * By default, watermarks consist of based on total system memory.
> > > + */
> > > +static bool per_node __read_mostly;
> > > +module_param(per_node, bool, 0600);
> > > +
> > > +/*
> > > + * Number of currently running DAMON worker threads
> > > + */
> > > +static unsigned long nr_kdamond __read_mostly;
> > > +module_param(nr_kdamond, ulong, 0400);
> >
> > I'd prefer to call this nr_kdamond*s*
> >
>
> I see.
>
> > > +
> > > +/*
> > > + * First PID of the DAMON threads
> > > + *
> > > + * If DAMON_RECLAIM is enabled, this becomes the first PID of the worker threads.
> > > * Else, -1.
> > > */
> > > -static int kdamond_pid __read_mostly = -1;
> > > -module_param(kdamond_pid, int, 0400);
> > > +static int kdamond_start_pid __read_mostly = -1;
> > > +module_param(kdamond_start_pid, int, 0400);
> >
> > This change could break old users. Let's keep the name as is and clarify the
> > fact that it's for only the first kdamond in the document.
>
> Got it, I will keep that name and update the DAMON document.
>
> >
> > As long as DAMON_RECLAIM works in the exclusive manner, users will still be
> > able to know all pids of kdamonds for DAMON_RECLAIM, as nr_kdamonds is also
> > provided.
>
> I will find some kind of way to show all pids of kdamonds.
>
> >
> > >
> > > /*
> > > * Number of memory regions that tried to be reclaimed.
> > > @@ -215,8 +229,8 @@ module_param(bytes_reclaimed_regions, ulong, 0400);
> > > static unsigned long nr_quota_exceeds __read_mostly;
> > > module_param(nr_quota_exceeds, ulong, 0400);
> > >
> > > -static struct damon_ctx *ctx;
> > > -static struct damon_target *target;
> > > +static struct damon_ctx *ctxs[MAX_NUMNODES];
> > > +static struct damon_target *targets[MAX_NUMNODES];
> > >
> > > struct damon_reclaim_ram_walk_arg {
> > > unsigned long start;
> > > @@ -251,7 +265,7 @@ static bool get_monitoring_region(unsigned long *start, unsigned long *end)
> > > return true;
> > > }
> > >
> > > -static struct damos *damon_reclaim_new_scheme(void)
> > > +static struct damos *damon_reclaim_new_scheme(int node)
> > > {
> > > struct damos_watermarks wmarks = {
> > > .metric = DAMOS_WMARK_FREE_MEM_RATE,
> > > @@ -259,6 +273,7 @@ static struct damos *damon_reclaim_new_scheme(void)
> > > .high = wmarks_high,
> > > .mid = wmarks_mid,
> > > .low = wmarks_low,
> > > + .node = node,
> > > };
> > > struct damos_quota quota = {
> > > /*
> > > @@ -290,56 +305,99 @@ static struct damos *damon_reclaim_new_scheme(void)
> > > return scheme;
> > > }
> > >
> > > -static int damon_reclaim_turn(bool on)
> > > +static int damon_reclaim_start(int nid)
> > > {
> > > struct damon_region *region;
> > > struct damos *scheme;
> > > int err;
> > > + unsigned long start, end;
> > >
> > > - if (!on) {
> > > - err = damon_stop(&ctx, 1);
> > > - if (!err)
> > > - kdamond_pid = -1;
> > > - return err;
> > > - }
> > > -
> > > - err = damon_set_attrs(ctx, sample_interval, aggr_interval, 0,
> > > + err = damon_set_attrs(ctxs[nid], sample_interval, aggr_interval, 0,
> > > min_nr_regions, max_nr_regions);
> > > if (err)
> > > return err;
> > >
> > > - if (monitor_region_start > monitor_region_end)
> > > - return -EINVAL;
> > > - if (!monitor_region_start && !monitor_region_end &&
> > > - !get_monitoring_region(&monitor_region_start,
> > > - &monitor_region_end))
> > > - return -EINVAL;
> > > + if (per_node) {
> > > + monitor_region_start = monitor_region_end = 0;
> > > +
> > > + start = PFN_PHYS(node_start_pfn(nid));
> > > + end = PFN_PHYS(node_start_pfn(nid) + node_present_pages(nid) - 1);
> > > + if (end <= start)
> > > + return -EINVAL;
> > > + } else {
> > > + if (!monitor_region_start && !monitor_region_end &&
> > > + !get_monitoring_region(&monitor_region_start,
> > > + &monitor_region_end))
> > > + return -EINVAL;
> > > + start = monitor_region_start;
> > > + end = monitor_region_end;
> > > + }
> > > +
> > > /* DAMON will free this on its own when finish monitoring */
> > > - region = damon_new_region(monitor_region_start, monitor_region_end);
> > > + region = damon_new_region(start, end);
> > > if (!region)
> > > return -ENOMEM;
> > > - damon_add_region(region, target);
> > > + damon_add_region(region, targets[nid]);
> > >
> > > /* Will be freed by 'damon_set_schemes()' below */
> > > - scheme = damon_reclaim_new_scheme();
> > > + scheme = damon_reclaim_new_scheme(nid);
> > > if (!scheme) {
> > > err = -ENOMEM;
> > > goto free_region_out;
> > > }
> > > - err = damon_set_schemes(ctx, &scheme, 1);
> > > +
> > > + err = damon_set_schemes(ctxs[nid], &scheme, 1);
> > > if (err)
> > > goto free_scheme_out;
> > >
> > > - err = damon_start(&ctx, 1);
> > > + err = damon_start_one(ctxs[nid]);
> >
> > This could surprise users assuming DAMON_RECLAIM would work in exclusive manner
> > as it was.
>
> Yes, I will drop this function following the next version.
>
> >
> > > if (!err) {
> > > - kdamond_pid = ctx->kdamond->pid;
> > > + if (kdamond_start_pid == -1)
> > > + kdamond_start_pid = ctxs[nid]->kdamond->pid;
> > > + nr_kdamond++;
> > > return 0;
> > > }
> > >
> > > free_scheme_out:
> > > damon_destroy_scheme(scheme);
> > > free_region_out:
> > > - damon_destroy_region(region, target);
> > > + damon_destroy_region(region, targets[nid]);
> > > +
> > > + return err;
> > > +}
> > > +
> > > +static int damon_reclaim_start_all(void)
> > > +{
> > > + int nid, err;
> > > +
> > > + if (!per_node)
> > > + return damon_reclaim_start(0);
> > > +
> > > + for_each_online_node(nid) {
> > > + err = damon_reclaim_start(nid);
> > > + if (err)
> > > + break;
> >
> > I'd prefer making contexts first and starting them at once in the exclusive
> > manner using damon_start().
> >
>
> Agree.
>
> > > + }
> > > +
> > > + return err;
> > > +}
> > > +
> > > +static int damon_reclaim_turn(bool on)
> > > +{
> > > + int err;
> > > +
> > > + if (!on) {
> > > + err = damon_stop(ctxs, nr_kdamond);
> > > + if (!err) {
> > > + kdamond_start_pid = -1;
> > > + nr_kdamond = 0;
> > > + monitor_region_start = 0;
> > > + monitor_region_end = 0;
> > > + }
> > > + return err;
> > > + }
> > > +
> > > + err = damon_reclaim_start_all();
> > > return err;
> > > }
> > >
> > > @@ -380,21 +438,24 @@ static int damon_reclaim_after_aggregation(struct damon_ctx *c)
> > >
> > > static int __init damon_reclaim_init(void)
> > > {
> > > - ctx = damon_new_ctx();
> > > - if (!ctx)
> > > - return -ENOMEM;
> > > -
> > > - if (damon_select_ops(ctx, DAMON_OPS_PADDR))
> > > - return -EINVAL;
> > > -
> > > - ctx->callback.after_aggregation = damon_reclaim_after_aggregation;
> > > -
> > > - target = damon_new_target();
> > > - if (!target) {
> > > - damon_destroy_ctx(ctx);
> > > - return -ENOMEM;
> > > + int nid;
> > > +
> > > + for_each_node(nid) {
> > > + ctxs[nid] = damon_new_ctx();
> > > + if (!ctxs[nid])
> > > + return -ENOMEM;
> > > +
> > > + if (damon_select_ops(ctxs[nid], DAMON_OPS_PADDR))
> > > + return -EINVAL;
> > > + ctxs[nid]->callback.after_aggregation = damon_reclaim_after_aggregation;
> > > +
> > > + targets[nid] = damon_new_target();
> > > + if (!targets[nid]) {
> > > + damon_destroy_ctx(ctxs[nid]);
> >
> > Shouldn't we also destroy previously allocated contexts?
>
> Yes, I think so. I will fix.
>
> >
> > > + return -ENOMEM;
> > > + }
> > > + damon_add_target(ctxs[nid], targets[nid]);
> > > }
> > > - damon_add_target(ctx, target);
> > >
> > > schedule_delayed_work(&damon_reclaim_timer, 0);
> > > return 0;
> > > --
> > > 2.17.1
> >
> >
> > Thanks,
> > SJ
>
>
> Thanks for the comments!
> Jonghyeon
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