Re: [PATCH 2/2] blk-plug: don't flush nested plug lists

From: Jeff Moyer
Date: Tue Apr 07 2015 - 10:47:49 EST

Ming Lei <tom.leiming@xxxxxxxxx> writes:

> Hi Jeff,

Hi, Ming. Thanks for reviewing!

>> Unpatched kernel:
>> Read B/W: 283,638 KB/s
>> Read Merges: 0
>> Patched kernel:
>> Read B/W: 873,224 KB/s
>> Read Merges: 2,046K
> The data is amazing, but maybe better to provide some latency
> data.

Yes, good point. I'll include the full fio output in the next posting.

>> Much of the patch involves modifying call sites to blk_start_plug,
>> since its signature is changed. The meat of the patch is actually
> I am wondering if the type of blk_start_plug has to be changed
> since the active plug is always the top plug with your patch, and
> blk_finish_plug() can find the active plug from current->plug.

That is a much simpler idea, thank you. I think blk_finish_plug
shouldn't take the plug argument, though, since it won't actually use

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