On Mon 09-01-23 15:16:31, Mel Gorman wrote: > From: NeilBrown <neilb@xxxxxxx> > > __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@xxxxxxxxxxxxxxxxxxxxx > Signed-off-by: NeilBrown <neilb@xxxxxxx> > Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> > Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Forgot to ack this one yesterday Acked-by: Michal Hocko <mhocko@xxxxxxxx> > --- > Documentation/mm/balance.rst | 2 +- > 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@xxxxxxx> > > -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 412b5a46374c..9db52bc4ce19 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 d34dc636b81c..46b4e6c414a3 100644 > --- a/lib/test_printf.c > +++ b/lib/test_printf.c > @@ -674,17 +674,17 @@ 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 23a37588073a..71b1111427f3 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 2217bab2dbb2..7244ab522028 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4086,13 +4086,14 @@ 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, > @@ -5057,14 +5058,6 @@ __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 e20656c431a4..173d407dce92 100644 > --- a/tools/perf/builtin-kmem.c > +++ b/tools/perf/builtin-kmem.c > @@ -641,7 +641,6 @@ 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 -- Michal Hocko SUSE Labs
