On Thu, Sep 17, 2015 at 11:19 PM, Jens Axboe <[email protected]> wrote: > On 09/17/2015 09:13 AM, Ming Lei wrote: >> >> biovecs has become immutable since v3.13, so it isn't necessary >> to allocate biovecs for the new cloned bios, then we can save >> one extra biovecs allocation/copy, and the allocation is often >> not fixed-length and a bit more expensive. >> >> For example, if the 'max_sectors_kb' of null blk's queue is set >> as 16(32 sectors) via sysfs just for making more splits, this patch >> can increase throught about ~70% in the sequential read test over >> null_blk(direct io, bs: 1M). > > > I'd be curious how this compares to before we did the splitting, not > exceeding the limits through bio_add_page() instead?
Let me show these test results: ---------------------------------------------------------------------------------- kernel | throught ---------------------------------------------------------------------------------- 4.3.0-rc1-next-20150916 | bw=12227MB/s, iops=12227 ---------------------------------------------------------------------------------- 4.3.0-rc1-next-20150916 with patch | bw=21011MB/s, iops=21011 ---------------------------------------------------------------------------------- v4.2 | bw=18959MB/s, iops=18958 ---------------------------------------------------------------------------------- So from the above, looks this patch is kind of fix for performance regression introduced by 54efd50bfd(block: make generic_make_request handle arbitrarily sized bios), :-) Thanks, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
