From e836a256e8fd579c9d7a3685f22981225a1ca451 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Wed, 12 Aug 2015 18:42:56 -0400 Subject: pmem: convert to generic memremap Kill arch_memremap_pmem() and just let the architecture specify the flags to be passed to memremap(). Default to writethrough by default. Suggested-by: Christoph Hellwig Reviewed-by: Christoph Hellwig Reviewed-by: Ross Zwisler Signed-off-by: Dan Williams --- arch/x86/include/asm/io.h | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) (limited to 'arch/x86/include/asm/io.h') diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h index cc9c61bc1abe..d241fbd5c87b 100644 --- a/arch/x86/include/asm/io.h +++ b/arch/x86/include/asm/io.h @@ -248,11 +248,7 @@ static inline void flush_write_buffers(void) #endif } -static inline void __pmem *arch_memremap_pmem(resource_size_t offset, - unsigned long size) -{ - return (void __force __pmem *) ioremap_cache(offset, size); -} +#define ARCH_MEMREMAP_PMEM MEMREMAP_WB #endif /* __KERNEL__ */ -- cgit From 67a3e8fe90156d41cd480d3dfbb40f3bc007c262 Mon Sep 17 00:00:00 2001 From: Ross Zwisler Date: Thu, 27 Aug 2015 13:14:20 -0600 Subject: nd_blk: change aperture mapping from WC to WB This should result in a pretty sizeable performance gain for reads. For rough comparison I did some simple read testing using PMEM to compare reads of write combining (WC) mappings vs write-back (WB). This was done on a random lab machine. PMEM reads from a write combining mapping: # dd of=/dev/null if=/dev/pmem0 bs=4096 count=100000 100000+0 records in 100000+0 records out 409600000 bytes (410 MB) copied, 9.2855 s, 44.1 MB/s PMEM reads from a write-back mapping: # dd of=/dev/null if=/dev/pmem0 bs=4096 count=1000000 1000000+0 records in 1000000+0 records out 4096000000 bytes (4.1 GB) copied, 3.44034 s, 1.2 GB/s To be able to safely support a write-back aperture I needed to add support for the "read flush" _DSM flag, as outlined in the DSM spec: http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf This flag tells the ND BLK driver that it needs to flush the cache lines associated with the aperture after the aperture is moved but before any new data is read. This ensures that any stale cache lines from the previous contents of the aperture will be discarded from the processor cache, and the new data will be read properly from the DIMM. We know that the cache lines are clean and will be discarded without any writeback because either a) the previous aperture operation was a read, and we never modified the contents of the aperture, or b) the previous aperture operation was a write and we must have written back the dirtied contents of the aperture to the DIMM before the I/O was completed. In order to add support for the "read flush" flag I needed to add a generic routine to invalidate cache lines, mmio_flush_range(). This is protected by the ARCH_HAS_MMIO_FLUSH Kconfig variable, and is currently only supported on x86. Signed-off-by: Ross Zwisler Signed-off-by: Dan Williams --- arch/x86/include/asm/io.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'arch/x86/include/asm/io.h') diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h index d241fbd5c87b..83ec9b1d77cc 100644 --- a/arch/x86/include/asm/io.h +++ b/arch/x86/include/asm/io.h @@ -248,8 +248,6 @@ static inline void flush_write_buffers(void) #endif } -#define ARCH_MEMREMAP_PMEM MEMREMAP_WB - #endif /* __KERNEL__ */ extern void native_io_delay(void); -- cgit