[Top] [All Lists]

Re: [PATCH 1/2] percpu_counter: batch size aware __percpu_counter_compar

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 1/2] percpu_counter: batch size aware __percpu_counter_compare()
From: Tejun Heo <tj@xxxxxxxxxx>
Date: Thu, 14 May 2015 11:02:30 -0400
Cc: xfs@xxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, peterz@xxxxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=9hCKGN3zioVEuaPX3SHw+nO2L5+0jXi3Y+cg4TZWotA=; b=ZPZ2u2/f4UYDZA/dETiRL+tc7Vl2iB4YPE1JJLZq6ymqbPB6bRs5hLbTTm90/w6Jb1 hdDC9AppUTasVUvbPRt21w162sHQihE8Jer+AIVet+Kon80rnd9gwCiwe/nLtBVpt2hX LH3du0UpV1upuMb8ps2s3MRa7T1cDovI4h9287oh0k0Aq2PMopoQ7iptWj1nBlC1SJCb TLzkBdTYu3d+baipP3ZUxJQ+//4Gv+cXyeCjHTQ5cztoS7xysvjaqSnB8TlQupY4GEQ+ aBtGTXlyvbLSqyt6IswxNuioeRIuSwF59PDJ9g/44amPm8dqNCHKSihyWtOeMkFHGDIe CldQ==
In-reply-to: <20150514005553.GD4316@dastard>
References: <1431474754-15764-1-git-send-email-david@xxxxxxxxxxxxx> <1431474754-15764-2-git-send-email-david@xxxxxxxxxxxxx> <20150513135919.GS11388@xxxxxxxxxxxxxxx> <20150514005553.GD4316@dastard>
Sender: Tejun Heo <htejun@xxxxxxxxx>
User-agent: Mutt/1.5.23 (2014-03-12)
On Thu, May 14, 2015 at 10:55:53AM +1000, Dave Chinner wrote:
> percpu_counter: batch size aware __percpu_counter_compare()
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> XFS uses non-stanard batch sizes for avoiding frequent global
> counter updates on it's allocated inode counters, as they increment
> or decrement in batches of 64 inodes. Hence the standard percpu
> counter batch of 32 means that the counter is effectively a global
> counter. Currently Xfs uses a batch size of 128 so that it doesn't
> take the global lock on every single modification.
> However, Xfs also needs to compare accurately against zero, which
> means we need to use percpu_counter_compare(), and that has a
> hard-coded batch size of 32, and hence will spuriously fail to
> detect when it is supposed to use precise comparisons and hence
> the accounting goes wrong.
> Add __percpu_counter_compare() to take a custom batch size so we can
> use it sanely in XFS and factor percpu_counter_compare() to use it.
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>

Acked-by: Tejun Heo <tj@xxxxxxxxxx>

Please feel free to route the patch however you see fit.



<Prev in Thread] Current Thread [Next in Thread>