mm/filemap.c: generic_file_buffered_read() now uses find_get_pages_contig
Convert generic_file_buffered_read() to get pages to read from in batches, and then copy data to userspace from many pages at once - in particular, we now don't touch any cachelines that might be contended while we're in the loop to copy data to userspace. This is is a performance improvement on workloads that do buffered reads with large blocksizes, and a very large performance improvement if that file is also being accessed concurrently by different threads. On smaller reads (512 bytes), there's a very small performance improvement (1%, within the margin of error). akpm: kernel test robot found a 32% speedup on one test: https://lkml.kernel.org/r/20201030081456.GY31092@shao2-debian Link: https://lkml.kernel.org/r/20201025212949.602194-3-kent.overstreet@gmail.com Signed-off-by:Kent Overstreet <kent.overstreet@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: kernel test robot <rong.a.chen@intel.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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723ef24b
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