| Message ID | 20210113012143.1201105-3-minchan@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Chunk Heap Support on DMA-HEAP | expand |
On 13.01.21 02:21, Minchan Kim wrote: > Contiguous memory allocation can be stalled due to waiting > on page writeback and/or page lock which causes unpredictable > delay. It's a unavoidable cost for the requestor to get *big* > contiguous memory but it's expensive for *small* contiguous > memory(e.g., order-4) because caller could retry the request > in diffrent range where would have easy migratable pages > without stalling. s/diffrent/different/ > > This patch introduce __GFP_NORETRY as compaction gfp_mask in > alloc_contig_range so it will fail fast without blocking > when it encounters pages needed waitting. s/waitting/waiting/ > > Signed-off-by: Minchan Kim <minchan@kernel.org> > --- > mm/page_alloc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 5b3923db9158..ff41ceb4db51 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -8489,12 +8489,16 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, > unsigned int nr_reclaimed; > unsigned long pfn = start; > unsigned int tries = 0; > + unsigned int max_tries = 5; > int ret = 0; > struct migration_target_control mtc = { > .nid = zone_to_nid(cc->zone), > .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL, > }; > > + if (cc->alloc_contig && cc->mode == MIGRATE_ASYNC) > + max_tries = 1; > + > migrate_prep(); > > while (pfn < end || !list_empty(&cc->migratepages)) { > @@ -8511,7 +8515,7 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, > break; > } > tries = 0; > - } else if (++tries == 5) { > + } else if (++tries == max_tries) { > ret = ret < 0 ? ret : -EBUSY; > break; > } > @@ -8562,7 +8566,7 @@ int alloc_contig_range(unsigned long start, unsigned long end, > .nr_migratepages = 0, > .order = -1, > .zone = page_zone(pfn_to_page(start)), > - .mode = MIGRATE_SYNC, > + .mode = gfp_mask & __GFP_NORETRY ? MIGRATE_ASYNC : MIGRATE_SYNC, > .ignore_skip_hint = true, > .no_set_skip_hint = true, > .gfp_mask = current_gfp_context(gfp_mask), > I'm fine with using gfp flags (e.g., __GFP_NORETRY) as long as they don't enable other implicit behavior (e.g., move draining X to the caller) that's hard to get from the flag name. IMHO, if we ever want to move draining to the caller, or change the behavior of alloc_contig_range() in different ways (e.g., disable PCP), we won't get around introducing a separate set of flags for alloc_contig_range(). Let's see what Michal thinks. Thanks!
On Wed, Jan 13, 2021 at 09:39:26AM +0100, David Hildenbrand wrote: > On 13.01.21 02:21, Minchan Kim wrote: > > Contiguous memory allocation can be stalled due to waiting > > on page writeback and/or page lock which causes unpredictable > > delay. It's a unavoidable cost for the requestor to get *big* > > contiguous memory but it's expensive for *small* contiguous > > memory(e.g., order-4) because caller could retry the request > > in diffrent range where would have easy migratable pages > > without stalling. > > s/diffrent/different/ > > > > > This patch introduce __GFP_NORETRY as compaction gfp_mask in > > alloc_contig_range so it will fail fast without blocking > > when it encounters pages needed waitting. > > s/waitting/waiting/ Fxed both. Thanks. Let me resend once I get some review. Michal, I appreciate if you could give an review before next revision. Thanks! > > > > > Signed-off-by: Minchan Kim <minchan@kernel.org> > > --- > > mm/page_alloc.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 5b3923db9158..ff41ceb4db51 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -8489,12 +8489,16 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, > > unsigned int nr_reclaimed; > > unsigned long pfn = start; > > unsigned int tries = 0; > > + unsigned int max_tries = 5; > > int ret = 0; > > struct migration_target_control mtc = { > > .nid = zone_to_nid(cc->zone), > > .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL, > > }; > > > > + if (cc->alloc_contig && cc->mode == MIGRATE_ASYNC) > > + max_tries = 1; > > + > > migrate_prep(); > > > > while (pfn < end || !list_empty(&cc->migratepages)) { > > @@ -8511,7 +8515,7 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, > > break; > > } > > tries = 0; > > - } else if (++tries == 5) { > > + } else if (++tries == max_tries) { > > ret = ret < 0 ? ret : -EBUSY; > > break; > > } > > @@ -8562,7 +8566,7 @@ int alloc_contig_range(unsigned long start, unsigned long end, > > .nr_migratepages = 0, > > .order = -1, > > .zone = page_zone(pfn_to_page(start)), > > - .mode = MIGRATE_SYNC, > > + .mode = gfp_mask & __GFP_NORETRY ? MIGRATE_ASYNC : MIGRATE_SYNC, > > .ignore_skip_hint = true, > > .no_set_skip_hint = true, > > .gfp_mask = current_gfp_context(gfp_mask), > > > > I'm fine with using gfp flags (e.g., __GFP_NORETRY) as long as they > don't enable other implicit behavior (e.g., move draining X to the > caller) that's hard to get from the flag name. > > IMHO, if we ever want to move draining to the caller, or change the > behavior of alloc_contig_range() in different ways (e.g., disable PCP), > we won't get around introducing a separate set of flags for > alloc_contig_range(). > > Let's see what Michal thinks. Thanks! > > -- > Thanks, > > David / dhildenb >
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 5b3923db9158..ff41ceb4db51 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -8489,12 +8489,16 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, unsigned int nr_reclaimed; unsigned long pfn = start; unsigned int tries = 0; + unsigned int max_tries = 5; int ret = 0; struct migration_target_control mtc = { .nid = zone_to_nid(cc->zone), .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL, }; + if (cc->alloc_contig && cc->mode == MIGRATE_ASYNC) + max_tries = 1; + migrate_prep(); while (pfn < end || !list_empty(&cc->migratepages)) { @@ -8511,7 +8515,7 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, break; } tries = 0; - } else if (++tries == 5) { + } else if (++tries == max_tries) { ret = ret < 0 ? ret : -EBUSY; break; } @@ -8562,7 +8566,7 @@ int alloc_contig_range(unsigned long start, unsigned long end, .nr_migratepages = 0, .order = -1, .zone = page_zone(pfn_to_page(start)), - .mode = MIGRATE_SYNC, + .mode = gfp_mask & __GFP_NORETRY ? MIGRATE_ASYNC : MIGRATE_SYNC, .ignore_skip_hint = true, .no_set_skip_hint = true, .gfp_mask = current_gfp_context(gfp_mask),
Contiguous memory allocation can be stalled due to waiting on page writeback and/or page lock which causes unpredictable delay. It's a unavoidable cost for the requestor to get *big* contiguous memory but it's expensive for *small* contiguous memory(e.g., order-4) because caller could retry the request in diffrent range where would have easy migratable pages without stalling. This patch introduce __GFP_NORETRY as compaction gfp_mask in alloc_contig_range so it will fail fast without blocking when it encounters pages needed waitting. Signed-off-by: Minchan Kim <minchan@kernel.org> --- mm/page_alloc.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)