Messages in this thread Patch in this message |  | | Date | Thu, 04 Jul 2002 16:54:40 -0700 | From | Andrew Morton <> | Subject | [patch 16/27] resurrect __GFP_HIGH |
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This patch reinstates __GFP_HIGH functionality.
__GFP_HIGH means "able to dip into the emergency pools". However, somewhere along the line this got broken. __GFP_HIGH ceased to do anything. Instead, !__GFP_WAIT is used to tell the page allocator to try harder.
__GFP_HIGH makes sense. The concepts of "unable to sleep" and "should try harder" are quite separate, and overloading !__GFP_WAIT to mean "should access emergency pools" seems wrong.
This patch fixes a problem in mempool_alloc(). mempool_alloc() tries the first allocation with __GFP_WAIT cleared. If that fails, it tries again with __GFP_WAIT enabled (if the caller can support __GFP_WAIT). So it is currently performing an atomic allocation first, even though the caller said that they're prepared to go in and call the page stealer.
I thought this was a mempool bug, but Ingo said:
> no, it's not GFP_ATOMIC. The important difference is __GFP_HIGH, which > triggers the intrusive highprio allocation mode. Otherwise gfp_nowait is > just a nonblocking allocation of the same type as the original gfp_mask. > ... > what i've added is a bit more subtle allocation method, with both > performance and balancing-correctness in mind: > > 1. allocate via gfp_mask, but nonblocking > 2. if failure => try to get from the pool if the pool is 'full enough'. > 3. if failure => allocate with gfp_mask [which might block] > > there is performance data that this method improves bounce-IO performance > significantly, because even under VM pressure (when gfp_mask would block) > we can still use up to 50% of the memory pool without blocking (and > without endangering deadlock-free allocation). Ie. the memory pool is also > a fast 'frontside cache' of memory elements.
Ingo was assuming that __GFP_HIGH was still functional. It isn't, and the mempool design wants it.
drivers/scsi/scsi_merge.c | 4 +++- include/linux/gfp.h | 10 +++++----- mm/page_alloc.c | 5 +---- mm/slab.c | 4 ++-- mm/vmscan.c | 3 +++ 5 files changed, 14 insertions(+), 12 deletions(-)
--- 2.5.24/mm/page_alloc.c~gfp_high Thu Jul 4 16:17:25 2002 +++ 2.5.24-akpm/mm/page_alloc.c Thu Jul 4 16:22:09 2002 @@ -272,8 +272,6 @@ static struct page * balance_classzone(z struct page * page = NULL; int __freed = 0; - if (!(gfp_mask & __GFP_WAIT)) - goto out; if (in_interrupt()) BUG(); @@ -333,7 +331,6 @@ static struct page * balance_classzone(z } current->nr_local_pages = 0; } - out: *freed = __freed; return page; } @@ -380,7 +377,7 @@ struct page * __alloc_pages(unsigned int break; local_min = z->pages_min; - if (!(gfp_mask & __GFP_WAIT)) + if (gfp_mask & __GFP_HIGH) local_min >>= 2; min += local_min; if (z->free_pages > min) { --- 2.5.24/include/linux/gfp.h~gfp_high Thu Jul 4 16:17:25 2002 +++ 2.5.24-akpm/include/linux/gfp.h Thu Jul 4 16:17:25 2002 @@ -18,14 +18,14 @@ #define __GFP_HIGHIO 0x80 /* Can start high mem physical IO? */ #define __GFP_FS 0x100 /* Can call down to low-level FS? */ -#define GFP_NOHIGHIO (__GFP_HIGH | __GFP_WAIT | __GFP_IO) -#define GFP_NOIO (__GFP_HIGH | __GFP_WAIT) -#define GFP_NOFS (__GFP_HIGH | __GFP_WAIT | __GFP_IO | __GFP_HIGHIO) +#define GFP_NOHIGHIO ( __GFP_WAIT | __GFP_IO) +#define GFP_NOIO ( __GFP_WAIT) +#define GFP_NOFS ( __GFP_WAIT | __GFP_IO | __GFP_HIGHIO) #define GFP_ATOMIC (__GFP_HIGH) #define GFP_USER ( __GFP_WAIT | __GFP_IO | __GFP_HIGHIO | __GFP_FS) #define GFP_HIGHUSER ( __GFP_WAIT | __GFP_IO | __GFP_HIGHIO | __GFP_FS | __GFP_HIGHMEM) -#define GFP_KERNEL (__GFP_HIGH | __GFP_WAIT | __GFP_IO | __GFP_HIGHIO | __GFP_FS) -#define GFP_NFS (__GFP_HIGH | __GFP_WAIT | __GFP_IO | __GFP_HIGHIO | __GFP_FS) +#define GFP_KERNEL ( __GFP_WAIT | __GFP_IO | __GFP_HIGHIO | __GFP_FS) +#define GFP_NFS ( __GFP_WAIT | __GFP_IO | __GFP_HIGHIO | __GFP_FS) #define GFP_KSWAPD ( __GFP_WAIT | __GFP_IO | __GFP_HIGHIO | __GFP_FS) /* Flag - indicates that the buffer will be suitable for DMA. Ignored on some --- 2.5.24/mm/vmscan.c~gfp_high Thu Jul 4 16:17:25 2002 +++ 2.5.24-akpm/mm/vmscan.c Thu Jul 4 16:22:09 2002 @@ -52,6 +52,9 @@ static inline int is_page_cache_freeable * So PF_MEMALLOC is dropped here. This causes the slab allocations to fail * earlier, so radix-tree nodes will then be allocated from the mempool * reserves. + * + * We're still using __GFP_HIGH for radix-tree node allocations, so some of + * the emergency pools are available - just not all of them. */ static inline int swap_out_add_to_swap_cache(struct page *page, swp_entry_t entry) --- 2.5.24/mm/slab.c~gfp_high Thu Jul 4 16:17:25 2002 +++ 2.5.24-akpm/mm/slab.c Thu Jul 4 16:17:25 2002 @@ -1153,12 +1153,12 @@ static int kmem_cache_grow (kmem_cache_t * in kmem_cache_alloc(). If a caller is seriously mis-behaving they * will eventually be caught here (where it matters). */ - if (in_interrupt() && (flags & SLAB_LEVEL_MASK) != SLAB_ATOMIC) + if (in_interrupt() && (flags & __GFP_WAIT)) BUG(); ctor_flags = SLAB_CTOR_CONSTRUCTOR; local_flags = (flags & SLAB_LEVEL_MASK); - if (local_flags == SLAB_ATOMIC) + if (!(local_flags & __GFP_WAIT)) /* * Not allowed to sleep. Need to tell a constructor about * this - it might need to know... --- 2.5.24/drivers/scsi/scsi_merge.c~gfp_high Thu Jul 4 16:17:25 2002 +++ 2.5.24-akpm/drivers/scsi/scsi_merge.c Thu Jul 4 16:17:25 2002 @@ -74,8 +74,10 @@ int scsi_init_io(Scsi_Cmnd *SCpnt) SCpnt->use_sg = count; gfp_mask = GFP_NOIO; - if (in_interrupt()) + if (in_interrupt()) { gfp_mask &= ~__GFP_WAIT; + gfp_mask |= __GFP_HIGH; + } /* * if sg table allocation fails, requeue request later. - - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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