| Message ID | 20221129151701.23261-7-mgorman@techsingularity.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Discard __GFP_ATOMIC | expand |
On 11/29/22 16:17, Mel Gorman wrote: > From: NeilBrown <neilb@suse.de> > > __GFP_ATOMIC serves little purpose. Its main effect is to set > ALLOC_HARDER which adds a few little boosts to increase the chance of an > allocation succeeding, one of which is to lower the water-mark at which it > will succeed. > > It is *always* paired with __GFP_HIGH which sets ALLOC_HIGH which also > adjusts this watermark. It is probable that other users of __GFP_HIGH > should benefit from the other little bonuses that __GFP_ATOMIC gets. > > __GFP_ATOMIC also gives a warning if used with __GFP_DIRECT_RECLAIM. > There is little point to this. We already get a might_sleep() warning if > __GFP_DIRECT_RECLAIM is set. > > __GFP_ATOMIC allows the "watermark_boost" to be side-stepped. It is > probable that testing ALLOC_HARDER is a better fit here. > > __GFP_ATOMIC is used by tegra-smmu.c to check if the allocation might > sleep. This should test __GFP_DIRECT_RECLAIM instead. > > This patch: > - removes __GFP_ATOMIC > - allows __GFP_HIGH allocations to ignore watermark boosting as well > as GFP_ATOMIC requests. > - makes other adjustments as suggested by the above. > > The net result is not change to GFP_ATOMIC allocations. Other > allocations that use __GFP_HIGH will benefit from a few different extra > privileges. This affects: > xen, dm, md, ntfs3 > the vermillion frame buffer > hibernation > ksm > swap > all of which likely produce more benefit than cost if these selected > allocation are more likely to succeed quickly. > > [mgorman: Minor adjustments to rework on top of a series] > Link: https://lkml.kernel.org/r/163712397076.13692.4727608274002939094@noble.neil.brown.name > Signed-off-by: NeilBrown <neilb@suse.de> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Just a nit below. > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4081,13 +4081,14 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, > if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags, > free_pages)) > return true; > + > /* > - * Ignore watermark boosting for GFP_ATOMIC order-0 allocations > + * Ignore watermark boosting for GFP_HIGH order-0 allocations There's no GFP_HIGH. We could either keep GFP_ATOMIC here if we want to talk about the high-level flag combo, or __GFP_HIGH if about the low-level detail. We're deep in the page allocator implementation so the latter would be OK. > * when checking the min watermark. The min watermark is the > * point where boosting is ignored so that kswapd is woken up > * when below the low watermark. > */ > - if (unlikely(!order && (gfp_mask & __GFP_ATOMIC) && z->watermark_boost > + if (unlikely(!order && (alloc_flags & ALLOC_MIN_RESERVE) && z->watermark_boost
On Thu, Dec 08, 2022 at 07:17:48PM +0100, Vlastimil Babka wrote: > > @@ -4081,13 +4081,14 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, > > if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags, > > free_pages)) > > return true; > > + > > /* > > - * Ignore watermark boosting for GFP_ATOMIC order-0 allocations > > + * Ignore watermark boosting for GFP_HIGH order-0 allocations > > There's no GFP_HIGH. We could either keep GFP_ATOMIC here if we want to talk > about the high-level flag combo, or __GFP_HIGH if about the low-level > detail. We're deep in the page allocator implementation so the latter would > be OK. > Fixed
Hi Mel, On Tue, Nov 29, 2022 at 03:17:01PM +0000, Mel Gorman wrote: > From: NeilBrown <neilb@suse.de> > > __GFP_ATOMIC serves little purpose. Its main effect is to set > ALLOC_HARDER which adds a few little boosts to increase the chance of an > allocation succeeding, one of which is to lower the water-mark at which it > will succeed. > > It is *always* paired with __GFP_HIGH which sets ALLOC_HIGH which also > adjusts this watermark. It is probable that other users of __GFP_HIGH > should benefit from the other little bonuses that __GFP_ATOMIC gets. > > __GFP_ATOMIC also gives a warning if used with __GFP_DIRECT_RECLAIM. > There is little point to this. We already get a might_sleep() warning if > __GFP_DIRECT_RECLAIM is set. > > __GFP_ATOMIC allows the "watermark_boost" to be side-stepped. It is > probable that testing ALLOC_HARDER is a better fit here. > > __GFP_ATOMIC is used by tegra-smmu.c to check if the allocation might > sleep. This should test __GFP_DIRECT_RECLAIM instead. > > This patch: > - removes __GFP_ATOMIC > - allows __GFP_HIGH allocations to ignore watermark boosting as well > as GFP_ATOMIC requests. > - makes other adjustments as suggested by the above. > > The net result is not change to GFP_ATOMIC allocations. Other > allocations that use __GFP_HIGH will benefit from a few different extra > privileges. This affects: > xen, dm, md, ntfs3 > the vermillion frame buffer > hibernation > ksm > swap > all of which likely produce more benefit than cost if these selected > allocation are more likely to succeed quickly. > > [mgorman: Minor adjustments to rework on top of a series] > Link: https://lkml.kernel.org/r/163712397076.13692.4727608274002939094@noble.neil.brown.name > Signed-off-by: NeilBrown <neilb@suse.de> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > --- > Documentation/mm/balance.rst | 2 +- Documentation/core-api/memory-allocation.rst needs an update as well, and there are other mentions of GFP_ATOMIC in Documentation/ > drivers/iommu/tegra-smmu.c | 4 ++-- > include/linux/gfp_types.h | 12 ++++-------- > include/trace/events/mmflags.h | 1 - > lib/test_printf.c | 8 ++++---- > mm/internal.h | 2 +- > mm/page_alloc.c | 13 +++---------- > tools/perf/builtin-kmem.c | 1 - > 8 files changed, 15 insertions(+), 28 deletions(-) > > diff --git a/Documentation/mm/balance.rst b/Documentation/mm/balance.rst > index 6a1fadf3e173..e38e9d83c1c7 100644 > --- a/Documentation/mm/balance.rst > +++ b/Documentation/mm/balance.rst > @@ -6,7 +6,7 @@ Memory Balancing > > Started Jan 2000 by Kanoj Sarcar <kanoj@sgi.com> > > -Memory balancing is needed for !__GFP_ATOMIC and !__GFP_KSWAPD_RECLAIM as > +Memory balancing is needed for !__GFP_HIGH and !__GFP_KSWAPD_RECLAIM as > well as for non __GFP_IO allocations. > > The first reason why a caller may avoid reclaim is that the caller can not > diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c > index 5b1af40221ec..af8d0e685260 100644 > --- a/drivers/iommu/tegra-smmu.c > +++ b/drivers/iommu/tegra-smmu.c > @@ -671,12 +671,12 @@ static struct page *as_get_pde_page(struct tegra_smmu_as *as, > * allocate page in a sleeping context if GFP flags permit. Hence > * spinlock needs to be unlocked and re-locked after allocation. > */ > - if (!(gfp & __GFP_ATOMIC)) > + if (gfpflags_allow_blocking(gfp)) > spin_unlock_irqrestore(&as->lock, *flags); > > page = alloc_page(gfp | __GFP_DMA | __GFP_ZERO); > > - if (!(gfp & __GFP_ATOMIC)) > + if (gfpflags_allow_blocking(gfp)) > spin_lock_irqsave(&as->lock, *flags); > > /* > diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h > index d88c46ca82e1..5088637fe5c2 100644 > --- a/include/linux/gfp_types.h > +++ b/include/linux/gfp_types.h > @@ -31,7 +31,7 @@ typedef unsigned int __bitwise gfp_t; > #define ___GFP_IO 0x40u > #define ___GFP_FS 0x80u > #define ___GFP_ZERO 0x100u > -#define ___GFP_ATOMIC 0x200u > +/* 0x200u unused */ > #define ___GFP_DIRECT_RECLAIM 0x400u > #define ___GFP_KSWAPD_RECLAIM 0x800u > #define ___GFP_WRITE 0x1000u > @@ -116,11 +116,8 @@ typedef unsigned int __bitwise gfp_t; > * > * %__GFP_HIGH indicates that the caller is high-priority and that granting > * the request is necessary before the system can make forward progress. > - * For example, creating an IO context to clean pages. > - * > - * %__GFP_ATOMIC indicates that the caller cannot reclaim or sleep and is > - * high priority. Users are typically interrupt handlers. This may be > - * used in conjunction with %__GFP_HIGH > + * For example creating an IO context to clean pages and requests > + * from atomic context. > * > * %__GFP_MEMALLOC allows access to all memory. This should only be used when > * the caller guarantees the allocation will allow more memory to be freed > @@ -135,7 +132,6 @@ typedef unsigned int __bitwise gfp_t; > * %__GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves. > * This takes precedence over the %__GFP_MEMALLOC flag if both are set. > */ > -#define __GFP_ATOMIC ((__force gfp_t)___GFP_ATOMIC) > #define __GFP_HIGH ((__force gfp_t)___GFP_HIGH) > #define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC) > #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC) > @@ -329,7 +325,7 @@ typedef unsigned int __bitwise gfp_t; > * version does not attempt reclaim/compaction at all and is by default used > * in page fault path, while the non-light is used by khugepaged. > */ > -#define GFP_ATOMIC (__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM) > +#define GFP_ATOMIC (__GFP_HIGH|__GFP_KSWAPD_RECLAIM) > #define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS) > #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT) > #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM) > diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h > index e87cb2b80ed3..11524cda4a95 100644 > --- a/include/trace/events/mmflags.h > +++ b/include/trace/events/mmflags.h > @@ -31,7 +31,6 @@ > gfpflag_string(__GFP_HIGHMEM), \ > gfpflag_string(GFP_DMA32), \ > gfpflag_string(__GFP_HIGH), \ > - gfpflag_string(__GFP_ATOMIC), \ > gfpflag_string(__GFP_IO), \ > gfpflag_string(__GFP_FS), \ > gfpflag_string(__GFP_NOWARN), \ > diff --git a/lib/test_printf.c b/lib/test_printf.c > index 4bd15a593fbd..fe13de1bed5f 100644 > --- a/lib/test_printf.c > +++ b/lib/test_printf.c > @@ -686,17 +686,17 @@ flags(void) > gfp = GFP_ATOMIC|__GFP_DMA; > test("GFP_ATOMIC|GFP_DMA", "%pGg", &gfp); > > - gfp = __GFP_ATOMIC; > - test("__GFP_ATOMIC", "%pGg", &gfp); > + gfp = __GFP_HIGH; > + test("__GFP_HIGH", "%pGg", &gfp); > > /* Any flags not translated by the table should remain numeric */ > gfp = ~__GFP_BITS_MASK; > snprintf(cmp_buffer, BUF_SIZE, "%#lx", (unsigned long) gfp); > test(cmp_buffer, "%pGg", &gfp); > > - snprintf(cmp_buffer, BUF_SIZE, "__GFP_ATOMIC|%#lx", > + snprintf(cmp_buffer, BUF_SIZE, "__GFP_HIGH|%#lx", > (unsigned long) gfp); > - gfp |= __GFP_ATOMIC; > + gfp |= __GFP_HIGH; > test(cmp_buffer, "%pGg", &gfp); > > kfree(cmp_buffer); > diff --git a/mm/internal.h b/mm/internal.h > index 98b1e526559d..48926b290cd5 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -24,7 +24,7 @@ struct folio_batch; > #define GFP_RECLAIM_MASK (__GFP_RECLAIM|__GFP_HIGH|__GFP_IO|__GFP_FS|\ > __GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_NOFAIL|\ > __GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC|\ > - __GFP_ATOMIC|__GFP_NOLOCKDEP) > + __GFP_NOLOCKDEP) > > /* The GFP flags allowed during early boot */ > #define GFP_BOOT_MASK (__GFP_BITS_MASK & ~(__GFP_RECLAIM|__GFP_IO|__GFP_FS)) > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 6bee987ec9a3..ad6c4705a79d 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4081,13 +4081,14 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, > if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags, > free_pages)) > return true; > + > /* > - * Ignore watermark boosting for GFP_ATOMIC order-0 allocations > + * Ignore watermark boosting for GFP_HIGH order-0 allocations > * when checking the min watermark. The min watermark is the > * point where boosting is ignored so that kswapd is woken up > * when below the low watermark. > */ > - if (unlikely(!order && (gfp_mask & __GFP_ATOMIC) && z->watermark_boost > + if (unlikely(!order && (alloc_flags & ALLOC_MIN_RESERVE) && z->watermark_boost > && ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) { > mark = z->_watermark[WMARK_MIN]; > return __zone_watermark_ok(z, order, mark, highest_zoneidx, > @@ -5052,14 +5053,6 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > unsigned int zonelist_iter_cookie; > int reserve_flags; > > - /* > - * We also sanity check to catch abuse of atomic reserves being used by > - * callers that are not in atomic context. > - */ > - if (WARN_ON_ONCE((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) == > - (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM))) > - gfp_mask &= ~__GFP_ATOMIC; > - > restart: > compaction_retries = 0; > no_progress_loops = 0; > diff --git a/tools/perf/builtin-kmem.c b/tools/perf/builtin-kmem.c > index ebfab2ca1702..4a06d83f2ac5 100644 > --- a/tools/perf/builtin-kmem.c > +++ b/tools/perf/builtin-kmem.c > @@ -640,7 +640,6 @@ static const struct { > { "__GFP_HIGHMEM", "HM" }, > { "GFP_DMA32", "D32" }, > { "__GFP_HIGH", "H" }, > - { "__GFP_ATOMIC", "_A" }, > { "__GFP_IO", "I" }, > { "__GFP_FS", "F" }, > { "__GFP_NOWARN", "NWR" }, > -- > 2.35.3 > >
On Fri, 06 Jan 2023, Mike Rapoport wrote: > Hi Mel, > > On Tue, Nov 29, 2022 at 03:17:01PM +0000, Mel Gorman wrote: > > From: NeilBrown <neilb@suse.de> > > > > __GFP_ATOMIC serves little purpose. Its main effect is to set > > ALLOC_HARDER which adds a few little boosts to increase the chance of an > > allocation succeeding, one of which is to lower the water-mark at which it > > will succeed. > > > > It is *always* paired with __GFP_HIGH which sets ALLOC_HIGH which also > > adjusts this watermark. It is probable that other users of __GFP_HIGH > > should benefit from the other little bonuses that __GFP_ATOMIC gets. > > > > __GFP_ATOMIC also gives a warning if used with __GFP_DIRECT_RECLAIM. > > There is little point to this. We already get a might_sleep() warning if > > __GFP_DIRECT_RECLAIM is set. > > > > __GFP_ATOMIC allows the "watermark_boost" to be side-stepped. It is > > probable that testing ALLOC_HARDER is a better fit here. > > > > __GFP_ATOMIC is used by tegra-smmu.c to check if the allocation might > > sleep. This should test __GFP_DIRECT_RECLAIM instead. > > > > This patch: > > - removes __GFP_ATOMIC > > - allows __GFP_HIGH allocations to ignore watermark boosting as well > > as GFP_ATOMIC requests. > > - makes other adjustments as suggested by the above. > > > > The net result is not change to GFP_ATOMIC allocations. Other > > allocations that use __GFP_HIGH will benefit from a few different extra > > privileges. This affects: > > xen, dm, md, ntfs3 > > the vermillion frame buffer > > hibernation > > ksm > > swap > > all of which likely produce more benefit than cost if these selected > > allocation are more likely to succeed quickly. > > > > [mgorman: Minor adjustments to rework on top of a series] > > Link: https://lkml.kernel.org/r/163712397076.13692.4727608274002939094@noble.neil.brown.name > > Signed-off-by: NeilBrown <neilb@suse.de> > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > > --- > > Documentation/mm/balance.rst | 2 +- > > Documentation/core-api/memory-allocation.rst needs an update as well, and > there are other mentions of GFP_ATOMIC in Documentation/ Note that this patch removes __GFP_ATOMIC, but does not change the behaviour of GFP_ATOMIC. So I don't believe there is any other documentation that need changing. Thanks, NeilBrown > > > drivers/iommu/tegra-smmu.c | 4 ++-- > > include/linux/gfp_types.h | 12 ++++-------- > > include/trace/events/mmflags.h | 1 - > > lib/test_printf.c | 8 ++++---- > > mm/internal.h | 2 +- > > mm/page_alloc.c | 13 +++---------- > > tools/perf/builtin-kmem.c | 1 - > > 8 files changed, 15 insertions(+), 28 deletions(-) > > > > diff --git a/Documentation/mm/balance.rst b/Documentation/mm/balance.rst > > index 6a1fadf3e173..e38e9d83c1c7 100644 > > --- a/Documentation/mm/balance.rst > > +++ b/Documentation/mm/balance.rst > > @@ -6,7 +6,7 @@ Memory Balancing > > > > Started Jan 2000 by Kanoj Sarcar <kanoj@sgi.com> > > > > -Memory balancing is needed for !__GFP_ATOMIC and !__GFP_KSWAPD_RECLAIM as > > +Memory balancing is needed for !__GFP_HIGH and !__GFP_KSWAPD_RECLAIM as > > well as for non __GFP_IO allocations. > > > > The first reason why a caller may avoid reclaim is that the caller can not > > diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c > > index 5b1af40221ec..af8d0e685260 100644 > > --- a/drivers/iommu/tegra-smmu.c > > +++ b/drivers/iommu/tegra-smmu.c > > @@ -671,12 +671,12 @@ static struct page *as_get_pde_page(struct tegra_smmu_as *as, > > * allocate page in a sleeping context if GFP flags permit. Hence > > * spinlock needs to be unlocked and re-locked after allocation. > > */ > > - if (!(gfp & __GFP_ATOMIC)) > > + if (gfpflags_allow_blocking(gfp)) > > spin_unlock_irqrestore(&as->lock, *flags); > > > > page = alloc_page(gfp | __GFP_DMA | __GFP_ZERO); > > > > - if (!(gfp & __GFP_ATOMIC)) > > + if (gfpflags_allow_blocking(gfp)) > > spin_lock_irqsave(&as->lock, *flags); > > > > /* > > diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h > > index d88c46ca82e1..5088637fe5c2 100644 > > --- a/include/linux/gfp_types.h > > +++ b/include/linux/gfp_types.h > > @@ -31,7 +31,7 @@ typedef unsigned int __bitwise gfp_t; > > #define ___GFP_IO 0x40u > > #define ___GFP_FS 0x80u > > #define ___GFP_ZERO 0x100u > > -#define ___GFP_ATOMIC 0x200u > > +/* 0x200u unused */ > > #define ___GFP_DIRECT_RECLAIM 0x400u > > #define ___GFP_KSWAPD_RECLAIM 0x800u > > #define ___GFP_WRITE 0x1000u > > @@ -116,11 +116,8 @@ typedef unsigned int __bitwise gfp_t; > > * > > * %__GFP_HIGH indicates that the caller is high-priority and that granting > > * the request is necessary before the system can make forward progress. > > - * For example, creating an IO context to clean pages. > > - * > > - * %__GFP_ATOMIC indicates that the caller cannot reclaim or sleep and is > > - * high priority. Users are typically interrupt handlers. This may be > > - * used in conjunction with %__GFP_HIGH > > + * For example creating an IO context to clean pages and requests > > + * from atomic context. > > * > > * %__GFP_MEMALLOC allows access to all memory. This should only be used when > > * the caller guarantees the allocation will allow more memory to be freed > > @@ -135,7 +132,6 @@ typedef unsigned int __bitwise gfp_t; > > * %__GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves. > > * This takes precedence over the %__GFP_MEMALLOC flag if both are set. > > */ > > -#define __GFP_ATOMIC ((__force gfp_t)___GFP_ATOMIC) > > #define __GFP_HIGH ((__force gfp_t)___GFP_HIGH) > > #define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC) > > #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC) > > @@ -329,7 +325,7 @@ typedef unsigned int __bitwise gfp_t; > > * version does not attempt reclaim/compaction at all and is by default used > > * in page fault path, while the non-light is used by khugepaged. > > */ > > -#define GFP_ATOMIC (__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM) > > +#define GFP_ATOMIC (__GFP_HIGH|__GFP_KSWAPD_RECLAIM) > > #define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS) > > #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT) > > #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM) > > diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h > > index e87cb2b80ed3..11524cda4a95 100644 > > --- a/include/trace/events/mmflags.h > > +++ b/include/trace/events/mmflags.h > > @@ -31,7 +31,6 @@ > > gfpflag_string(__GFP_HIGHMEM), \ > > gfpflag_string(GFP_DMA32), \ > > gfpflag_string(__GFP_HIGH), \ > > - gfpflag_string(__GFP_ATOMIC), \ > > gfpflag_string(__GFP_IO), \ > > gfpflag_string(__GFP_FS), \ > > gfpflag_string(__GFP_NOWARN), \ > > diff --git a/lib/test_printf.c b/lib/test_printf.c > > index 4bd15a593fbd..fe13de1bed5f 100644 > > --- a/lib/test_printf.c > > +++ b/lib/test_printf.c > > @@ -686,17 +686,17 @@ flags(void) > > gfp = GFP_ATOMIC|__GFP_DMA; > > test("GFP_ATOMIC|GFP_DMA", "%pGg", &gfp); > > > > - gfp = __GFP_ATOMIC; > > - test("__GFP_ATOMIC", "%pGg", &gfp); > > + gfp = __GFP_HIGH; > > + test("__GFP_HIGH", "%pGg", &gfp); > > > > /* Any flags not translated by the table should remain numeric */ > > gfp = ~__GFP_BITS_MASK; > > snprintf(cmp_buffer, BUF_SIZE, "%#lx", (unsigned long) gfp); > > test(cmp_buffer, "%pGg", &gfp); > > > > - snprintf(cmp_buffer, BUF_SIZE, "__GFP_ATOMIC|%#lx", > > + snprintf(cmp_buffer, BUF_SIZE, "__GFP_HIGH|%#lx", > > (unsigned long) gfp); > > - gfp |= __GFP_ATOMIC; > > + gfp |= __GFP_HIGH; > > test(cmp_buffer, "%pGg", &gfp); > > > > kfree(cmp_buffer); > > diff --git a/mm/internal.h b/mm/internal.h > > index 98b1e526559d..48926b290cd5 100644 > > --- a/mm/internal.h > > +++ b/mm/internal.h > > @@ -24,7 +24,7 @@ struct folio_batch; > > #define GFP_RECLAIM_MASK (__GFP_RECLAIM|__GFP_HIGH|__GFP_IO|__GFP_FS|\ > > __GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_NOFAIL|\ > > __GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC|\ > > - __GFP_ATOMIC|__GFP_NOLOCKDEP) > > + __GFP_NOLOCKDEP) > > > > /* The GFP flags allowed during early boot */ > > #define GFP_BOOT_MASK (__GFP_BITS_MASK & ~(__GFP_RECLAIM|__GFP_IO|__GFP_FS)) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 6bee987ec9a3..ad6c4705a79d 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -4081,13 +4081,14 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, > > if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags, > > free_pages)) > > return true; > > + > > /* > > - * Ignore watermark boosting for GFP_ATOMIC order-0 allocations > > + * Ignore watermark boosting for GFP_HIGH order-0 allocations > > * when checking the min watermark. The min watermark is the > > * point where boosting is ignored so that kswapd is woken up > > * when below the low watermark. > > */ > > - if (unlikely(!order && (gfp_mask & __GFP_ATOMIC) && z->watermark_boost > > + if (unlikely(!order && (alloc_flags & ALLOC_MIN_RESERVE) && z->watermark_boost > > && ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) { > > mark = z->_watermark[WMARK_MIN]; > > return __zone_watermark_ok(z, order, mark, highest_zoneidx, > > @@ -5052,14 +5053,6 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > > unsigned int zonelist_iter_cookie; > > int reserve_flags; > > > > - /* > > - * We also sanity check to catch abuse of atomic reserves being used by > > - * callers that are not in atomic context. > > - */ > > - if (WARN_ON_ONCE((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) == > > - (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM))) > > - gfp_mask &= ~__GFP_ATOMIC; > > - > > restart: > > compaction_retries = 0; > > no_progress_loops = 0; > > diff --git a/tools/perf/builtin-kmem.c b/tools/perf/builtin-kmem.c > > index ebfab2ca1702..4a06d83f2ac5 100644 > > --- a/tools/perf/builtin-kmem.c > > +++ b/tools/perf/builtin-kmem.c > > @@ -640,7 +640,6 @@ static const struct { > > { "__GFP_HIGHMEM", "HM" }, > > { "GFP_DMA32", "D32" }, > > { "__GFP_HIGH", "H" }, > > - { "__GFP_ATOMIC", "_A" }, > > { "__GFP_IO", "I" }, > > { "__GFP_FS", "F" }, > > { "__GFP_NOWARN", "NWR" }, > > -- > > 2.35.3 > > > > > > -- > Sincerely yours, > Mike. >
On Thu, Jan 05, 2023 at 03:49:44PM +0200, Mike Rapoport wrote: > Hi Mel, > > On Tue, Nov 29, 2022 at 03:17:01PM +0000, Mel Gorman wrote: > > From: NeilBrown <neilb@suse.de> > > > > __GFP_ATOMIC serves little purpose. Its main effect is to set > > ALLOC_HARDER which adds a few little boosts to increase the chance of an > > allocation succeeding, one of which is to lower the water-mark at which it > > will succeed. > > > > It is *always* paired with __GFP_HIGH which sets ALLOC_HIGH which also > > adjusts this watermark. It is probable that other users of __GFP_HIGH > > should benefit from the other little bonuses that __GFP_ATOMIC gets. > > > > __GFP_ATOMIC also gives a warning if used with __GFP_DIRECT_RECLAIM. > > There is little point to this. We already get a might_sleep() warning if > > __GFP_DIRECT_RECLAIM is set. > > > > __GFP_ATOMIC allows the "watermark_boost" to be side-stepped. It is > > probable that testing ALLOC_HARDER is a better fit here. > > > > __GFP_ATOMIC is used by tegra-smmu.c to check if the allocation might > > sleep. This should test __GFP_DIRECT_RECLAIM instead. > > > > This patch: > > - removes __GFP_ATOMIC > > - allows __GFP_HIGH allocations to ignore watermark boosting as well > > as GFP_ATOMIC requests. > > - makes other adjustments as suggested by the above. > > > > The net result is not change to GFP_ATOMIC allocations. Other > > allocations that use __GFP_HIGH will benefit from a few different extra > > privileges. This affects: > > xen, dm, md, ntfs3 > > the vermillion frame buffer > > hibernation > > ksm > > swap > > all of which likely produce more benefit than cost if these selected > > allocation are more likely to succeed quickly. > > > > [mgorman: Minor adjustments to rework on top of a series] > > Link: https://lkml.kernel.org/r/163712397076.13692.4727608274002939094@noble.neil.brown.name > > Signed-off-by: NeilBrown <neilb@suse.de> > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > > --- > > Documentation/mm/balance.rst | 2 +- > > Documentation/core-api/memory-allocation.rst needs an update as well, and > there are other mentions of GFP_ATOMIC in Documentation/ > What part do you think needs updating in that file? There are two references to GFP_ATOMIC in that file, one about accessing reserves and another about non-sleeping allocations and the accuracy does not change after the series. If anything, this statement should change because it invites GFP_ATOMIC abuse for spurious reasons * If you think that accessing memory reserves is justified and the kernel will be stressed unless allocation succeeds, you may use ``GFP_ATOMIC``. There are other references to GFP_ATOMIC in Documentation/ that are are a little inaccurate but not in a way that is harmful and is not changed by the series. For example; GFP_ATOMIC requests are kernel internal allocations that must be satisfied, immediately. The kernel may drop some request, in rare cases even panic, if a GFP_ATOMIC alloc fails. This is a stronger statement than GFP_ATOMIC deserves but it's close enough in the given context.
On Fri, Jan 06, 2023 at 09:35:24AM +0000, Mel Gorman wrote: > On Thu, Jan 05, 2023 at 03:49:44PM +0200, Mike Rapoport wrote: > > Hi Mel, > > > > On Tue, Nov 29, 2022 at 03:17:01PM +0000, Mel Gorman wrote: > > > From: NeilBrown <neilb@suse.de> > > > > > > __GFP_ATOMIC serves little purpose. Its main effect is to set > > > ALLOC_HARDER which adds a few little boosts to increase the chance of an > > > allocation succeeding, one of which is to lower the water-mark at which it > > > will succeed. > > > > > > It is *always* paired with __GFP_HIGH which sets ALLOC_HIGH which also > > > adjusts this watermark. It is probable that other users of __GFP_HIGH > > > should benefit from the other little bonuses that __GFP_ATOMIC gets. > > > > > > __GFP_ATOMIC also gives a warning if used with __GFP_DIRECT_RECLAIM. > > > There is little point to this. We already get a might_sleep() warning if > > > __GFP_DIRECT_RECLAIM is set. > > > > > > __GFP_ATOMIC allows the "watermark_boost" to be side-stepped. It is > > > probable that testing ALLOC_HARDER is a better fit here. > > > > > > __GFP_ATOMIC is used by tegra-smmu.c to check if the allocation might > > > sleep. This should test __GFP_DIRECT_RECLAIM instead. > > > > > > This patch: > > > - removes __GFP_ATOMIC > > > - allows __GFP_HIGH allocations to ignore watermark boosting as well > > > as GFP_ATOMIC requests. > > > - makes other adjustments as suggested by the above. > > > > > > The net result is not change to GFP_ATOMIC allocations. Other > > > allocations that use __GFP_HIGH will benefit from a few different extra > > > privileges. This affects: > > > xen, dm, md, ntfs3 > > > the vermillion frame buffer > > > hibernation > > > ksm > > > swap > > > all of which likely produce more benefit than cost if these selected > > > allocation are more likely to succeed quickly. > > > > > > [mgorman: Minor adjustments to rework on top of a series] > > > Link: https://lkml.kernel.org/r/163712397076.13692.4727608274002939094@noble.neil.brown.name > > > Signed-off-by: NeilBrown <neilb@suse.de> > > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > > > --- > > > Documentation/mm/balance.rst | 2 +- > > > > Documentation/core-api/memory-allocation.rst needs an update as well, and > > there are other mentions of GFP_ATOMIC in Documentation/ > > > > What part do you think needs updating in that file? > > There are two references to GFP_ATOMIC in that file, one about accessing > reserves and another about non-sleeping allocations and the accuracy > does not change after the series. You are right, I got confused. > If anything, this statement should change because it invites GFP_ATOMIC > abuse for spurious reasons > > * If you think that accessing memory reserves is justified and the kernel > will be stressed unless allocation succeeds, you may use ``GFP_ATOMIC``. Care to send a patch? ;-) > There are other references to GFP_ATOMIC in Documentation/ that are are a > little inaccurate but not in a way that is harmful and is not changed by > the series. For example; > > GFP_ATOMIC requests are kernel internal allocations that must > be satisfied, immediately. The kernel may drop some request, > in rare cases even panic, if a GFP_ATOMIC alloc fails. > > This is a stronger statement than GFP_ATOMIC deserves but it's close enough > in the given context. > > -- > Mel Gorman > SUSE Labs >
diff --git a/Documentation/mm/balance.rst b/Documentation/mm/balance.rst index 6a1fadf3e173..e38e9d83c1c7 100644 --- a/Documentation/mm/balance.rst +++ b/Documentation/mm/balance.rst @@ -6,7 +6,7 @@ Memory Balancing Started Jan 2000 by Kanoj Sarcar <kanoj@sgi.com> -Memory balancing is needed for !__GFP_ATOMIC and !__GFP_KSWAPD_RECLAIM as +Memory balancing is needed for !__GFP_HIGH and !__GFP_KSWAPD_RECLAIM as well as for non __GFP_IO allocations. The first reason why a caller may avoid reclaim is that the caller can not diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c index 5b1af40221ec..af8d0e685260 100644 --- a/drivers/iommu/tegra-smmu.c +++ b/drivers/iommu/tegra-smmu.c @@ -671,12 +671,12 @@ static struct page *as_get_pde_page(struct tegra_smmu_as *as, * allocate page in a sleeping context if GFP flags permit. Hence * spinlock needs to be unlocked and re-locked after allocation. */ - if (!(gfp & __GFP_ATOMIC)) + if (gfpflags_allow_blocking(gfp)) spin_unlock_irqrestore(&as->lock, *flags); page = alloc_page(gfp | __GFP_DMA | __GFP_ZERO); - if (!(gfp & __GFP_ATOMIC)) + if (gfpflags_allow_blocking(gfp)) spin_lock_irqsave(&as->lock, *flags); /* diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h index d88c46ca82e1..5088637fe5c2 100644 --- a/include/linux/gfp_types.h +++ b/include/linux/gfp_types.h @@ -31,7 +31,7 @@ typedef unsigned int __bitwise gfp_t; #define ___GFP_IO 0x40u #define ___GFP_FS 0x80u #define ___GFP_ZERO 0x100u -#define ___GFP_ATOMIC 0x200u +/* 0x200u unused */ #define ___GFP_DIRECT_RECLAIM 0x400u #define ___GFP_KSWAPD_RECLAIM 0x800u #define ___GFP_WRITE 0x1000u @@ -116,11 +116,8 @@ typedef unsigned int __bitwise gfp_t; * * %__GFP_HIGH indicates that the caller is high-priority and that granting * the request is necessary before the system can make forward progress. - * For example, creating an IO context to clean pages. - * - * %__GFP_ATOMIC indicates that the caller cannot reclaim or sleep and is - * high priority. Users are typically interrupt handlers. This may be - * used in conjunction with %__GFP_HIGH + * For example creating an IO context to clean pages and requests + * from atomic context. * * %__GFP_MEMALLOC allows access to all memory. This should only be used when * the caller guarantees the allocation will allow more memory to be freed @@ -135,7 +132,6 @@ typedef unsigned int __bitwise gfp_t; * %__GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves. * This takes precedence over the %__GFP_MEMALLOC flag if both are set. */ -#define __GFP_ATOMIC ((__force gfp_t)___GFP_ATOMIC) #define __GFP_HIGH ((__force gfp_t)___GFP_HIGH) #define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC) #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC) @@ -329,7 +325,7 @@ typedef unsigned int __bitwise gfp_t; * version does not attempt reclaim/compaction at all and is by default used * in page fault path, while the non-light is used by khugepaged. */ -#define GFP_ATOMIC (__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM) +#define GFP_ATOMIC (__GFP_HIGH|__GFP_KSWAPD_RECLAIM) #define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS) #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT) #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM) diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h index e87cb2b80ed3..11524cda4a95 100644 --- a/include/trace/events/mmflags.h +++ b/include/trace/events/mmflags.h @@ -31,7 +31,6 @@ gfpflag_string(__GFP_HIGHMEM), \ gfpflag_string(GFP_DMA32), \ gfpflag_string(__GFP_HIGH), \ - gfpflag_string(__GFP_ATOMIC), \ gfpflag_string(__GFP_IO), \ gfpflag_string(__GFP_FS), \ gfpflag_string(__GFP_NOWARN), \ diff --git a/lib/test_printf.c b/lib/test_printf.c index 4bd15a593fbd..fe13de1bed5f 100644 --- a/lib/test_printf.c +++ b/lib/test_printf.c @@ -686,17 +686,17 @@ flags(void) gfp = GFP_ATOMIC|__GFP_DMA; test("GFP_ATOMIC|GFP_DMA", "%pGg", &gfp); - gfp = __GFP_ATOMIC; - test("__GFP_ATOMIC", "%pGg", &gfp); + gfp = __GFP_HIGH; + test("__GFP_HIGH", "%pGg", &gfp); /* Any flags not translated by the table should remain numeric */ gfp = ~__GFP_BITS_MASK; snprintf(cmp_buffer, BUF_SIZE, "%#lx", (unsigned long) gfp); test(cmp_buffer, "%pGg", &gfp); - snprintf(cmp_buffer, BUF_SIZE, "__GFP_ATOMIC|%#lx", + snprintf(cmp_buffer, BUF_SIZE, "__GFP_HIGH|%#lx", (unsigned long) gfp); - gfp |= __GFP_ATOMIC; + gfp |= __GFP_HIGH; test(cmp_buffer, "%pGg", &gfp); kfree(cmp_buffer); diff --git a/mm/internal.h b/mm/internal.h index 98b1e526559d..48926b290cd5 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -24,7 +24,7 @@ struct folio_batch; #define GFP_RECLAIM_MASK (__GFP_RECLAIM|__GFP_HIGH|__GFP_IO|__GFP_FS|\ __GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_NOFAIL|\ __GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC|\ - __GFP_ATOMIC|__GFP_NOLOCKDEP) + __GFP_NOLOCKDEP) /* The GFP flags allowed during early boot */ #define GFP_BOOT_MASK (__GFP_BITS_MASK & ~(__GFP_RECLAIM|__GFP_IO|__GFP_FS)) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6bee987ec9a3..ad6c4705a79d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4081,13 +4081,14 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags, free_pages)) return true; + /* - * Ignore watermark boosting for GFP_ATOMIC order-0 allocations + * Ignore watermark boosting for GFP_HIGH order-0 allocations * when checking the min watermark. The min watermark is the * point where boosting is ignored so that kswapd is woken up * when below the low watermark. */ - if (unlikely(!order && (gfp_mask & __GFP_ATOMIC) && z->watermark_boost + if (unlikely(!order && (alloc_flags & ALLOC_MIN_RESERVE) && z->watermark_boost && ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) { mark = z->_watermark[WMARK_MIN]; return __zone_watermark_ok(z, order, mark, highest_zoneidx, @@ -5052,14 +5053,6 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, unsigned int zonelist_iter_cookie; int reserve_flags; - /* - * We also sanity check to catch abuse of atomic reserves being used by - * callers that are not in atomic context. - */ - if (WARN_ON_ONCE((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) == - (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM))) - gfp_mask &= ~__GFP_ATOMIC; - restart: compaction_retries = 0; no_progress_loops = 0; diff --git a/tools/perf/builtin-kmem.c b/tools/perf/builtin-kmem.c index ebfab2ca1702..4a06d83f2ac5 100644 --- a/tools/perf/builtin-kmem.c +++ b/tools/perf/builtin-kmem.c @@ -640,7 +640,6 @@ static const struct { { "__GFP_HIGHMEM", "HM" }, { "GFP_DMA32", "D32" }, { "__GFP_HIGH", "H" }, - { "__GFP_ATOMIC", "_A" }, { "__GFP_IO", "I" }, { "__GFP_FS", "F" }, { "__GFP_NOWARN", "NWR" },