[Top] [All Lists]

Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Thu, 19 Mar 2015 18:29:47 -0700
Cc: Mel Gorman <mgorman@xxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Aneesh Kumar <aneesh.kumar@xxxxxxxxxxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Linux-MM <linux-mm@xxxxxxxxx>, xfs@xxxxxxxxxxx, ppc-dev <linuxppc-dev@xxxxxxxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=q2nWIs84qaOfjtOg/RrplxWRKrGXIB8ELjMSgPGfL94=; b=YVtkj3/YZyzXk0WkX+YVc1v6ANyqS3MnOxiQeo37z8xijZDto4t1rqJOjwLUvl8NAm WcxxoGDlJB1jLuAims5eaY92YXvVz2EorwVUI8adItiTp8wxM5SSN14fR9hDJ0ZhZoFs lf+8XgNO7UmZv7MjkF/M2G1eknRiV5J6qEIJG8L39Jr5RkTZrrx5Hz397aGTR+iYcVw9 BwUjedDdt17c16NcQZNJP+js+Kfn6yZrqUk43oOcYDDfm4s0YrKfa2cZRPPNG+zUSYZX ozdHrUW3ubW8Zbmi3ggNHc7BYkVtdxoG1EC7GRoiBvUpQm+aCg3uF8tODYLc4f6Lhs2D qujg==
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=q2nWIs84qaOfjtOg/RrplxWRKrGXIB8ELjMSgPGfL94=; b=ImrjmSHMJ3AEwuZTSezSWiOisfNXBxBU92/7CcT8jqqiAZZoP2CCgSqu7BOvdOl8vu 2k3uP81KhWgsNBce8fhIcRFAo/k8yijEE/btgml5etfrJZuC5IlaFPxStnh86pGaxMXJ 243O1q7vPTtumeZL9fjGhLFL7z5lKsyInqdX4=
In-reply-to: <20150320002311.GG28621@dastard>
References: <20150317070655.GB10105@dastard> <CA+55aFzdLnFdku-gnm3mGbeS=QauYBNkFQKYXJAGkrMd2jKXhw@xxxxxxxxxxxxxx> <20150317205104.GA28621@dastard> <CA+55aFzSPcNgxw4GC7aAV1r0P5LniyVVC66COz=3cgMcx73Nag@xxxxxxxxxxxxxx> <20150317220840.GC28621@dastard> <CA+55aFwne-fe_Gg-_GTUo+iOAbbNpLBa264JqSFkH79EULyAqw@xxxxxxxxxxxxxx> <CA+55aFy-Mw74rAdLMMMUgnsG3ZttMWVNGz7CXZJY7q9fqyRYfg@xxxxxxxxxxxxxx> <CA+55aFyxA9u2cVzV+S7TSY9ZvRXCX=z22YAbi9mdPVBKmqgR5g@xxxxxxxxxxxxxx> <20150319224143.GI10105@dastard> <CA+55aFy5UeNnFUTi619cs3b9Up2NQ1wbuyvcCS614+o3=z=wBQ@xxxxxxxxxxxxxx> <20150320002311.GG28621@dastard>
Sender: linus971@xxxxxxxxx
On Thu, Mar 19, 2015 at 5:23 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> Bit more variance there than the pte checking, but runtime
> difference is in the noise - 5m4s vs 4m54s - and profiles are
> identical to the pte checking version.

Ahh, so that "!(vma->vm_flags & VM_WRITE)" test works _almost_ as well
as the original !pte_write() test.

Now, can you check that on top of rc4? If I've gotten everything
right, we now have:

 - plain 3.19 (pte_write): 4m54s
 - 3.19 with vm_flags & VM_WRITE: 5m4s
 - 3.19 with pte_dirty: 5m20s

so the pte_dirty version seems to have been a bad choice indeed.

For 4.0-rc4, (which uses pte_dirty) you had 7m50s, so it's still
_much_ worse, but I'm wondering whether that VM_WRITE test will at
least shrink the difference like it does for 3.19.

And the VM_WRITE test should be stable and not have any subtle
interaction with the other changes that the numa pte things
introduced. It would be good to see if the profiles then pop something
*else* up as the performance difference (which I'm sure will remain,
since the 7m50s was so far off).


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