linux-5.15/balance_pgdat()
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開始行:
*参照元 [#fe988b01]
#backlinks
*説明 [#kd03c0f4]
-パス: [[linux-5.15/mm/vmscan.c]]
-FIXME: これは何？
--説明
**引数 [#m608ea88]
-pg_data_t *pgdat
--メモリノード。
--[[linux-5.15/pg_data_t]]
-int order
--オーダー。
-int highest_zoneidx
--メモリを確保する最大のゾーンインデックス値。この値以下...
**返り値 [#j1c0272a]
-int
--
**参考 [#i2d498e3]
*実装 [#v3b2814b]
/*
* For kswapd, balance_pgdat() will reclaim pages across...
* that are eligible for use by the caller until at leas...
* balanced.
*
* Returns the order kswapd finished reclaiming at.
*
* kswapd scans the zones in the highmem->normal->dma di...
* zones which have free_pages > high_wmark_pages(zone),...
* found to have free_pages <= high_wmark_pages(zone), a...
* or lower is eligible for reclaim until at least one u...
* balanced.
*/
static int balance_pgdat(pg_data_t *pgdat, int order, in...
{
int i;
unsigned long nr_soft_reclaimed;
unsigned long nr_soft_scanned;
unsigned long pflags;
unsigned long nr_boost_reclaim;
unsigned long zone_boosts[MAX_NR_ZONES] = { 0, };
bool boosted;
struct zone *zone;
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.order = order,
.may_unmap = 1,
};
set_task_reclaim_state(current, &sc.reclaim_state);
psi_memstall_enter(&pflags);
__fs_reclaim_acquire(_THIS_IP_);
count_vm_event(PAGEOUTRUN);
-
--[[linux-5.15/zone]]
--[[linux-5.15/scan_control]]
--[[linux-5.15/set_task_reclaim_state()]]
--[[linux-5.15/psi_memstall_enter()]]
--[[linux-5.15/__fs_reclaim_acquire()]]
--[[linux-5.15/count_vm_event()]]
/*
* Account for the reclaim boost. Note that the zone bo...
* place so that parallel allocations that are near the...
* stall or direct reclaim until kswapd is finished.
*/
nr_boost_reclaim = 0;
for (i = 0; i <= highest_zoneidx; i++) {
zone = pgdat->node_zones + i;
if (!managed_zone(zone))
continue;
nr_boost_reclaim += zone->watermark_boost;
zone_boosts[i] = zone->watermark_boost;
}
boosted = nr_boost_reclaim;
-
--[[linux-5.15/managed_zone()]]
restart:
set_reclaim_active(pgdat, highest_zoneidx);
sc.priority = DEF_PRIORITY;
-
--[[linux-5.15/set_reclaim_active()]]
do {
unsigned long nr_reclaimed = sc.nr_reclaimed;
bool raise_priority = true;
bool balanced;
bool ret;
sc.reclaim_idx = highest_zoneidx;
/*
* If the number of buffer_heads exceeds the maximum a...
* then consider reclaiming from all zones. This has a...
* purpose -- on 64-bit systems it is expected that
* buffer_heads are stripped during active rotation. O...
* systems, highmem pages can pin lowmem memory and sh...
* buffers can relieve lowmem pressure. Reclaim may st...
* go ahead if all eligible zones for the original all...
* request are balanced to avoid excessive reclaim fro...
*/
if (buffer_heads_over_limit) {
for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
zone = pgdat->node_zones + i;
if (!managed_zone(zone))
continue;
sc.reclaim_idx = i;
break;
}
}
-buffer_heads_over_limitが有効ならhightest_zoneidxを無視...
--[[linux-5.15/managed_zone()]]
/*
* If the pgdat is imbalanced then ignore boosting and...
* the watermarks for a later time and restart. Note t...
* zone watermarks will be still reset at the end of b...
* on the grounds that the normal reclaim should be en...
* re-evaluate if boosting is required when kswapd nex...
*/
balanced = pgdat_balanced(pgdat, sc.order, highest_zon...
if (!balanced && nr_boost_reclaim) {
nr_boost_reclaim = 0;
goto restart;
}
-メモリノードの空きページのバランスが取れていれば、boost...
--[[linux-5.15/pgdat_balanced()]]
/*
* If boosting is not active then only reclaim if ther...
* eligible zones. Note that sc.reclaim_idx is not use...
* buffer_heads_over_limit may have adjusted it.
*/
if (!nr_boost_reclaim && balanced)
goto out;
-boost値が0でなく、メモリノードの空きページのバランスが取...
/* Limit the priority of boosting to avoid reclaim wri...
if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2)
raise_priority = false;
/*
* Do not writeback or swap pages for boosted reclaim....
* intent is to relieve pressure not issue sub-optimal...
* from reclaim context. If no pages are reclaimed, the
* reclaim will be aborted.
*/
sc.may_writepage = !laptop_mode && !nr_boost_reclaim;
sc.may_swap = !nr_boost_reclaim;
/*
* Do some background aging of the anon list, to give
* pages a chance to be referenced before reclaiming. ...
* pages are rotated regardless of classzone as this is
* about consistent aging.
*/
age_active_anon(pgdat, &sc);
-
--[[linux-5.15/age_active_anon()]]
/*
* If we're getting trouble reclaiming, start doing wr...
* even in laptop mode.
*/
if (sc.priority < DEF_PRIORITY - 2)
sc.may_writepage = 1;
/* Call soft limit reclaim before calling shrink_node....
sc.nr_scanned = 0;
nr_soft_scanned = 0;
nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgda...
sc.gfp_mask, &nr_soft_scanned);
sc.nr_reclaimed += nr_soft_reclaimed;
-
--[[linux-5.15/mem_cgroup_soft_limit_reclaim()]]
/*
* There should be no need to raise the scanning prior...
* enough pages are already being scanned that that high
* watermark would be met at 100% efficiency.
*/
if (kswapd_shrink_node(pgdat, &sc))
raise_priority = false;
-
--[[linux-5.15/kswapd_shrink_node()]]
/*
* If the low watermark is met there is no need for pr...
* to be throttled on pfmemalloc_wait as they should n...
* able to safely make forward progress. Wake them
*/
if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
allow_direct_reclaim(pgdat))
wake_up_all(&pgdat->pfmemalloc_wait);
-
--[[linux-5.15/waitqueue_active()]]
--[[linux-5.15/allow_direct_reclaim()]]
--[[linux-5.15/wake_up_all()]]
/* Check if kswapd should be suspending */
__fs_reclaim_release(_THIS_IP_);
ret = try_to_freeze();
__fs_reclaim_acquire(_THIS_IP_);
if (ret || kthread_should_stop())
break;
-
--[[linux-5.15/__fs_reclaim_release()]]
--[[linux-5.15/try_to_freeze()]]
--[[linux-5.15/kthread_should_stop()]]
/*
* Raise priority if scanning rate is too low or there...
* progress in reclaiming pages
*/
nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed);
/*
* If reclaim made no progress for a boost, stop recla...
* IO cannot be queued and it could be an infinite loo...
* extreme circumstances.
*/
if (nr_boost_reclaim && !nr_reclaimed)
break;
if (raise_priority || !nr_reclaimed)
sc.priority--;
} while (sc.priority >= 1);
if (!sc.nr_reclaimed)
pgdat->kswapd_failures++;
out:
clear_reclaim_active(pgdat, highest_zoneidx);
-
--[[linux-5.15/clear_reclaim_active()]]
/* If reclaim was boosted, account for the reclaim done...
if (boosted) {
unsigned long flags;
for (i = 0; i <= highest_zoneidx; i++) {
if (!zone_boosts[i])
continue;
/* Increments are under the zone lock */
zone = pgdat->node_zones + i;
spin_lock_irqsave(&zone->lock, flags);
zone->watermark_boost -= min(zone->watermark_boost, z...
spin_unlock_irqrestore(&zone->lock, flags);
}
/*
* As there is now likely space, wakeup kcompact to de...
* pageblocks.
*/
wakeup_kcompactd(pgdat, pageblock_order, highest_zonei...
}
-
--[[linux-5.15/spin_lock_irqsave()]]
--[[linux-5.15/spin_unlock_irqsave()]]
--[[linux-5.15/wakeup_kcompactd()]]
snapshot_refaults(NULL, pgdat);
__fs_reclaim_release(_THIS_IP_);
psi_memstall_leave(&pflags);
set_task_reclaim_state(current, NULL);
-
--[[linux-5.15/snapshot_refaults()]]
--[[linux-5.15/__fs_reclaim_release()]]
--[[linux-5.15/psi_memstall_leave()]]
--[[linux-5.15/set_task_reclaim_state()]]
/*
* Return the order kswapd stopped reclaiming at as
* prepare_kswapd_sleep() takes it into account. If ano...
* entered the allocator slow path while kswapd was awa...
* remain at the higher level.
*/
return sc.order;
}
*コメント [#m7833ae5]
終了行:
*参照元 [#fe988b01]
#backlinks
*説明 [#kd03c0f4]
-パス: [[linux-5.15/mm/vmscan.c]]
-FIXME: これは何？
--説明
**引数 [#m608ea88]
-pg_data_t *pgdat
--メモリノード。
--[[linux-5.15/pg_data_t]]
-int order
--オーダー。
-int highest_zoneidx
--メモリを確保する最大のゾーンインデックス値。この値以下...
**返り値 [#j1c0272a]
-int
--
**参考 [#i2d498e3]
*実装 [#v3b2814b]
/*
* For kswapd, balance_pgdat() will reclaim pages across...
* that are eligible for use by the caller until at leas...
* balanced.
*
* Returns the order kswapd finished reclaiming at.
*
* kswapd scans the zones in the highmem->normal->dma di...
* zones which have free_pages > high_wmark_pages(zone),...
* found to have free_pages <= high_wmark_pages(zone), a...
* or lower is eligible for reclaim until at least one u...
* balanced.
*/
static int balance_pgdat(pg_data_t *pgdat, int order, in...
{
int i;
unsigned long nr_soft_reclaimed;
unsigned long nr_soft_scanned;
unsigned long pflags;
unsigned long nr_boost_reclaim;
unsigned long zone_boosts[MAX_NR_ZONES] = { 0, };
bool boosted;
struct zone *zone;
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.order = order,
.may_unmap = 1,
};
set_task_reclaim_state(current, &sc.reclaim_state);
psi_memstall_enter(&pflags);
__fs_reclaim_acquire(_THIS_IP_);
count_vm_event(PAGEOUTRUN);
-
--[[linux-5.15/zone]]
--[[linux-5.15/scan_control]]
--[[linux-5.15/set_task_reclaim_state()]]
--[[linux-5.15/psi_memstall_enter()]]
--[[linux-5.15/__fs_reclaim_acquire()]]
--[[linux-5.15/count_vm_event()]]
/*
* Account for the reclaim boost. Note that the zone bo...
* place so that parallel allocations that are near the...
* stall or direct reclaim until kswapd is finished.
*/
nr_boost_reclaim = 0;
for (i = 0; i <= highest_zoneidx; i++) {
zone = pgdat->node_zones + i;
if (!managed_zone(zone))
continue;
nr_boost_reclaim += zone->watermark_boost;
zone_boosts[i] = zone->watermark_boost;
}
boosted = nr_boost_reclaim;
-
--[[linux-5.15/managed_zone()]]
restart:
set_reclaim_active(pgdat, highest_zoneidx);
sc.priority = DEF_PRIORITY;
-
--[[linux-5.15/set_reclaim_active()]]
do {
unsigned long nr_reclaimed = sc.nr_reclaimed;
bool raise_priority = true;
bool balanced;
bool ret;
sc.reclaim_idx = highest_zoneidx;
/*
* If the number of buffer_heads exceeds the maximum a...
* then consider reclaiming from all zones. This has a...
* purpose -- on 64-bit systems it is expected that
* buffer_heads are stripped during active rotation. O...
* systems, highmem pages can pin lowmem memory and sh...
* buffers can relieve lowmem pressure. Reclaim may st...
* go ahead if all eligible zones for the original all...
* request are balanced to avoid excessive reclaim fro...
*/
if (buffer_heads_over_limit) {
for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
zone = pgdat->node_zones + i;
if (!managed_zone(zone))
continue;
sc.reclaim_idx = i;
break;
}
}
-buffer_heads_over_limitが有効ならhightest_zoneidxを無視...
--[[linux-5.15/managed_zone()]]
/*
* If the pgdat is imbalanced then ignore boosting and...
* the watermarks for a later time and restart. Note t...
* zone watermarks will be still reset at the end of b...
* on the grounds that the normal reclaim should be en...
* re-evaluate if boosting is required when kswapd nex...
*/
balanced = pgdat_balanced(pgdat, sc.order, highest_zon...
if (!balanced && nr_boost_reclaim) {
nr_boost_reclaim = 0;
goto restart;
}
-メモリノードの空きページのバランスが取れていれば、boost...
--[[linux-5.15/pgdat_balanced()]]
/*
* If boosting is not active then only reclaim if ther...
* eligible zones. Note that sc.reclaim_idx is not use...
* buffer_heads_over_limit may have adjusted it.
*/
if (!nr_boost_reclaim && balanced)
goto out;
-boost値が0でなく、メモリノードの空きページのバランスが取...
/* Limit the priority of boosting to avoid reclaim wri...
if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2)
raise_priority = false;
/*
* Do not writeback or swap pages for boosted reclaim....
* intent is to relieve pressure not issue sub-optimal...
* from reclaim context. If no pages are reclaimed, the
* reclaim will be aborted.
*/
sc.may_writepage = !laptop_mode && !nr_boost_reclaim;
sc.may_swap = !nr_boost_reclaim;
/*
* Do some background aging of the anon list, to give
* pages a chance to be referenced before reclaiming. ...
* pages are rotated regardless of classzone as this is
* about consistent aging.
*/
age_active_anon(pgdat, &sc);
-
--[[linux-5.15/age_active_anon()]]
/*
* If we're getting trouble reclaiming, start doing wr...
* even in laptop mode.
*/
if (sc.priority < DEF_PRIORITY - 2)
sc.may_writepage = 1;
/* Call soft limit reclaim before calling shrink_node....
sc.nr_scanned = 0;
nr_soft_scanned = 0;
nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgda...
sc.gfp_mask, &nr_soft_scanned);
sc.nr_reclaimed += nr_soft_reclaimed;
-
--[[linux-5.15/mem_cgroup_soft_limit_reclaim()]]
/*
* There should be no need to raise the scanning prior...
* enough pages are already being scanned that that high
* watermark would be met at 100% efficiency.
*/
if (kswapd_shrink_node(pgdat, &sc))
raise_priority = false;
-
--[[linux-5.15/kswapd_shrink_node()]]
/*
* If the low watermark is met there is no need for pr...
* to be throttled on pfmemalloc_wait as they should n...
* able to safely make forward progress. Wake them
*/
if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
allow_direct_reclaim(pgdat))
wake_up_all(&pgdat->pfmemalloc_wait);
-
--[[linux-5.15/waitqueue_active()]]
--[[linux-5.15/allow_direct_reclaim()]]
--[[linux-5.15/wake_up_all()]]
/* Check if kswapd should be suspending */
__fs_reclaim_release(_THIS_IP_);
ret = try_to_freeze();
__fs_reclaim_acquire(_THIS_IP_);
if (ret || kthread_should_stop())
break;
-
--[[linux-5.15/__fs_reclaim_release()]]
--[[linux-5.15/try_to_freeze()]]
--[[linux-5.15/kthread_should_stop()]]
/*
* Raise priority if scanning rate is too low or there...
* progress in reclaiming pages
*/
nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed);
/*
* If reclaim made no progress for a boost, stop recla...
* IO cannot be queued and it could be an infinite loo...
* extreme circumstances.
*/
if (nr_boost_reclaim && !nr_reclaimed)
break;
if (raise_priority || !nr_reclaimed)
sc.priority--;
} while (sc.priority >= 1);
if (!sc.nr_reclaimed)
pgdat->kswapd_failures++;
out:
clear_reclaim_active(pgdat, highest_zoneidx);
-
--[[linux-5.15/clear_reclaim_active()]]
/* If reclaim was boosted, account for the reclaim done...
if (boosted) {
unsigned long flags;
for (i = 0; i <= highest_zoneidx; i++) {
if (!zone_boosts[i])
continue;
/* Increments are under the zone lock */
zone = pgdat->node_zones + i;
spin_lock_irqsave(&zone->lock, flags);
zone->watermark_boost -= min(zone->watermark_boost, z...
spin_unlock_irqrestore(&zone->lock, flags);
}
/*
* As there is now likely space, wakeup kcompact to de...
* pageblocks.
*/
wakeup_kcompactd(pgdat, pageblock_order, highest_zonei...
}
-
--[[linux-5.15/spin_lock_irqsave()]]
--[[linux-5.15/spin_unlock_irqsave()]]
--[[linux-5.15/wakeup_kcompactd()]]
snapshot_refaults(NULL, pgdat);
__fs_reclaim_release(_THIS_IP_);
psi_memstall_leave(&pflags);
set_task_reclaim_state(current, NULL);
-
--[[linux-5.15/snapshot_refaults()]]
--[[linux-5.15/__fs_reclaim_release()]]
--[[linux-5.15/psi_memstall_leave()]]
--[[linux-5.15/set_task_reclaim_state()]]
/*
* Return the order kswapd stopped reclaiming at as
* prepare_kswapd_sleep() takes it into account. If ano...
* entered the allocator slow path while kswapd was awa...
* remain at the higher level.
*/
return sc.order;
}
*コメント [#m7833ae5]
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