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Date: Tue, 20 Oct 2020 08:47:39 -0600 From: Jens Axboe <axboe@...nel.dk> To: Kent Overstreet <kent.overstreet@...il.com> Cc: linux-kernel <linux-kernel@...r.kernel.org>, fsdevel <linux-fsdevel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>, Kent Overstreet <kent.overstreet@...il.com>, Matthew Wilcox <willy@...radead.org> Subject: Re: [PATCH 2/2] fs: generic_file_buffered_read() now uses find_get_pages_contig On Sat, Oct 17, 2020 at 2:11 PM Kent Overstreet <kent.overstreet@...il.com> wrote: > > 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). I ran this through my buffered testing, and no ill effects observed. It also provides a nice boost on the read side for a mixed read/write verification workload I have. Reviewed-by: Jens Axboe <axboe@...nel.dk> -- Jens Axboe
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