linux-kernel - Re: [RFC][PATCH 0/3] Skip I/O merges when disabled

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Date:	Thu, 24 Apr 2008 16:38:59 -0400
From:	"Alan D. Brunelle" <Alan.Brunelle@...com>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 0/3] Skip I/O merges when disabled

Jens Axboe wrote:
> 
> The functionality is fine with me, merging is obviously a non-zero
> amount of cycles spent on IO and if you know it's in vain, may as well
> turn it off. One suggestion, though - if you add this as a performance
> rather than functionality change, I would suggest keeping the one-hit
> cache merge as that is essentially free. Better than free actually,
> since if you hit that merge point you'll be spending way less cycles
> than allocating+setting up a new request.
> 

With the patch below we retain the one-hit cache functionality. On a few
by-hand runs I'm seeing not much movement in the numbers (goodness). I'm
going to do a full 25 by 10-minute set of runs, and if things look OK,
I'll submit a new patch stream tomorrow.

Cheers,
Alan

View attachment "0004-Move-merge-skip-until-after-the-one-hit-check.patch" of type "text/x-patch" (1277 bytes)