Messages in this thread | | | Subject | Re: [PATCH] mm: don't cap request size based on read-ahead setting | From | Jens Axboe <> | Date | Wed, 16 Nov 2016 08:12:09 -0700 |
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On 11/16/2016 12:17 AM, Hillf Danton wrote: > On Wednesday, November 16, 2016 12:31 PM Jens Axboe wrote: >> @@ -369,10 +369,25 @@ ondemand_readahead(struct address_space *mapping, >> bool hit_readahead_marker, pgoff_t offset, >> unsigned long req_size) >> { >> - unsigned long max = ra->ra_pages; >> + unsigned long io_pages, max_pages; >> pgoff_t prev_offset; >> >> /* >> + * If bdi->io_pages is set, that indicates the (soft) max IO size >> + * per command for that device. If we have that available, use >> + * that as the max suitable read-ahead size for this IO. Instead of >> + * capping read-ahead at ra_pages if req_size is larger, we can go >> + * up to io_pages. If io_pages isn't set, fall back to using >> + * ra_pages as a safe max. >> + */ >> + io_pages = inode_to_bdi(mapping->host)->io_pages; >> + if (io_pages) { >> + max_pages = max_t(unsigned long, ra->ra_pages, req_size); >> + io_pages = min(io_pages, max_pages); > > Doubt if you mean > max_pages = min(io_pages, max_pages);
No, that is what I mean. We want the maximum of the RA setting and the user IO size, but the minimum of that and the device max command size.
-- Jens Axboe
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